Weaning

Management and prognosis of patients requiring prolonged mechanical ventilation

Author: MeiLan King Han, MD, MS
Section Editors: Polly E Parsons, MD; R Sean Morrison, MD
Deputy Editor: Geraldine Finlay, MD

All topics are updated as new evidence becomes available and our peer review process is complete.

Literature review current through: Apr 2022. | This topic last updated: Apr 25, 2022.

INTRODUCTIONProlonged mechanical ventilation (PMV) is defined by the Centers for Medicare and Medicaid Services in the United States as greater than 21 days of mechanical ventilation for at least six hours per day [1], although many studies have used an alternative duration to define PMV. It is estimated that between 4 and 13 percent of mechanically ventilated patients require PMV [2,3], resulting in between 7250 and 11,400 patients undergoing PMV at any one time [2]. PMV is associated with increased health care cost, morbidity, and mortality [2,3].

Issues related to PMV are reviewed here, including predictors, weaning, complications, and outcomes. Issues related to the evaluation and management of patients who are difficult to wean from mechanical ventilation, as well as the selection of such patients for transfer to a long-term acute care facility where PMV usually occurs, are discussed separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit".)

PREDICTORSPrediction of which patients will require PMV is discussed here, whereas prediction of successful liberation from mechanical ventilation is described elsewhere. (See "Weaning from mechanical ventilation: Readiness testing".)

There are no evidence-based predictors that can reliably identify patients who will require PMV. Studies have sought to identify such predictors, but their results are difficult to generalize because they examined varying durations of mechanical ventilation and specific patient populations. In addition, attempts to validate potential predictors have found poor sensitivity and specificity.

One of the few studies examining general medical and surgical intensive care unit (ICU) patients prospectively followed 5915 patients that required mechanical ventilation on the first day of their ICU admission. The relative contribution of various patient- and disease-related variables to the duration of mechanical ventilation was identified. The following variables were reported as being associated with an increased duration of mechanical ventilation, with their relative contribution shown in parentheses [4]:

●ICU admission due to pneumonia, acute respiratory distress syndrome (ARDS), neuromuscular disease, head trauma, or postoperative intracerebral hemorrhage (44.3 percent).

●Elevated Acute Physiology Score (APS) of the Acute Physiologic and Chronic Health Evaluation III (APACHE III) on the first day in the ICU (25 percent). The average duration of ventilation increased linearly with APS scores up to 75, but then declined with APS scores above 75 due to early mortality.

●Admission to the ICU from another ICU, another hospital, or the medical ward (6.1 percent). In contrast, admission from the operating room or recovery room was associated with a shorter duration of mechanical ventilation.

●Abnormal arterial carbon dioxide (PaCO2), serum blood urea nitrogen (BUN), serum creatinine, arterial pH, white blood cell count (WBC), or body temperature (4.8 percent) on the first day in the ICU.

●Extended inpatient length of stay prior to ICU admission (4.3 percent).

●Elevated respiratory rate on the first day in the ICU (3.5 percent).

●Admission to a large teaching hospital (3.4 percent).

●Low serum albumin on the first day in the ICU (2.9 percent).

●History of obstructive or restrictive lung disease (2.4 percent).

●Decreased ratio of arterial oxygen to fraction of inspired oxygen (PaO2/FiO2) on the first day in the ICU (2 percent). The average duration of mechanical ventilation increased as the PaO2/FiO2 ratio fell to 150 mmHg and then declined due to early mortality.

●Advanced age (1.1 percent). Average duration of mechanical ventilation increased with age up to 85 years and then declined due to early mortality.

Another predictive index that has been proposed is the I-TRACH score. An I-TRACH score (Intubation in the ICU, tachycardia [heart rate >110 beats per minute], renal dysfunction [urea nitrogen level >25 mmol/L], acidemia [pH <7.25], creatinine [<2.0 or >50 percent increase from baseline values] and decreased bicarbonate level [HCO3 <20 mmol/L]) greater than or equal to four was predictive of subsequent need for mechanical ventilation beyond 7 and 14 days at the time of intubation [5]. The sensitivity was 61.8 percent, specificity 82 percent, positive predictive value 45.7 percent, and negative predictive value 89.8 percent for predicting >14 days of mechanical ventilator support.

The development of critical illness polyneuropathy (CIP) appears to be a predictor of PMV. This was illustrated by an observational study of 64 patients deemed ready to wean from mechanical ventilation [6]. The patients with confirmed CIP required mechanical ventilation for a longer duration than patients without CIP (median of 34 versus 14 days) [6]. The relationship between CIP and duration of mechanical ventilation persisted after adjustment for potential confounders (odds ratio 15.5, 95% CI 4.55-52.3).

It is likely that peripheral weakness also predicts the duration of mechanical ventilation because it is a marker of respiratory muscle weakness. In an observational study of 116 patients who were mechanically ventilated for seven days or more, the Medical Research Council muscle strength score correlated with the maximal inspiratory pressure, maximal expiratory pressure and vital capacity [7]. (See "Neuromuscular weakness related to critical illness" and "Tests of respiratory muscle strength".)

PHYSIOLOGYThe imbalance created by an increased respiratory load and decreased respiratory muscle performance appears to be responsible for most cases of prolonged ventilatory dependence [8-10]:

●Increased respiratory muscle load was demonstrated by a study of 31 mechanically ventilated patients with chronic obstructive pulmonary disease who had their respiratory mechanics evaluated before and during a trial of spontaneous breathing [8]. Seventeen patients failed the spontaneous breathing trial (SBT) and returned to mechanical ventilation, while 14 patients tolerated the trial and were successfully extubated. The group that failed the SBT had larger absolute increases in dynamic lung elastance, intrinsic positive end-expiratory pressure (auto-PEEP), and inspiratory resistance during the SBT, findings suggestive of an increased respiratory muscle load.

●Decreased respiratory muscle performance was illustrated by a study of 31 ventilator dependent patients who had their respiratory mechanics evaluated during spontaneous breathing [10]. The patients had an increased respiratory drive (indicated by a decrease in the airway opening pressure at 0.1 s) and decreased respiratory muscle strength (indicated by a diminished maximum transdiaphragmatic pressure), findings suggestive of decreased respiratory muscle performance.

It has been suggested that PMV itself may contribute to decreased respiratory muscle performance [11], a hypothesis that is largely based upon evidence that short-term mechanical ventilation may induce respiratory muscle and diaphragmatic weakness. The degree to which this observation applies to patients undergoing PMV is unknown. (See "Physiologic and pathophysiologic consequences of mechanical ventilation", section on 'Diaphragm' and "Physiologic and pathophysiologic consequences of mechanical ventilation", section on 'Respiratory muscles'.)

Decreased central respiratory drive (ie, due to medications or central nervous system disease) is often considered a potential contributor to prolonged ventilatory dependence, but the evidence suggests that this is an infrequent cause of PMV [8,9], since most patients who fail to wean actually have an increased central respiratory drive.

ASSESSING PATIENT GOALS AND PREFERENCESFor patients who are unable to wean from invasive ventilation within one to three weeks of intubation, the next step is usually consideration of tracheostomy and transfer to a long-term assisted care facility. When approaching these decisions, we meet with the patient to review their current medical status, the likelihood of eventual weaning, and expected quality and duration of life should they remain ventilator dependent [12]. If the patient is not able to participate in decision-making, we meet with their designated decision-maker or, in the absence of a patient-designated decision-maker, with the patient's family. These discussions focus on the patient's goals and preferences for medical care in the context of expected outcomes of PMV [13]. When intensive care unit interventions are unlikely to accomplish the patient's goals, it is appropriate to raise the issue of transitioning to palliative care. (See "Communication in the ICU: Holding a meeting with families and caregivers" and "Communication of prognosis in palliative care" and "Withholding and withdrawing ventilatory support in adults in the intensive care unit" and "Advance care planning and advance directives".)

TRACHEOSTOMYMost patients who choose to continue with PMV will have a tracheostomy placed to facilitate comfort, communication, and transfer to a weaning facility. The timing, techniques, and outcomes of tracheostomy are discussed separately. (See "Tracheostomy: Rationale, indications, and contraindications".)

WEANINGProlonged ventilator dependence signifies either incomplete resolution of the illness that precipitated mechanical ventilation or the development of new problems. More than one factor is often responsible for weaning failure. This section describes the optimization of patients requiring PMV for weaning, as well as strategies for weaning. While ideally all patients would be weaned off of all ventilator support, in some patients persistent nocturnal mechanical ventilation or noninvasive ventilation may be required.

Optimization for weaning — Prior to weaning a patient who has required PMV, all potential causes of ventilator dependence should be identified and either corrected or optimized. In addition, factors that might not be the cause of the patient's respiratory failure, but could impair the weaning process, should be identified and managed. (See "Management of the difficult-to-wean adult patient in the intensive care unit", section on 'Identify and correct the cause'.)

Cardiovascular — Heart failure or ischemia can be induced by reduction of ventilatory support and cause weaning failure [14-18]. This was illustrated by the following studies:

●Ninety-three patients underwent continuous ST-segment monitoring while weaning from mechanical ventilation [17]. Myocardial ischemia was identified in six patients. Those patients with myocardial ischemia were more likely to fail weaning than those without (4 out of 6 patients versus 32 out of 87 patients).

●Fifteen mechanically ventilated patients with known cardiac disease failed spontaneous breathing trials [15]. During the trials, an increase in the pulmonary artery occlusion pressure (average increase from 8 to 25 mmHg) was noted in every patient. Following diuretic therapy with an average weight loss 0.5 kg, 9 of the 15 patients were successfully liberated from mechanical ventilation.

The management of heart failure and myocardial ischemia are reviewed separately. (See "Treatment and prognosis of heart failure with preserved ejection fraction" and "Chronic coronary syndrome: Overview of care" and "Overview of the management of heart failure with reduced ejection fraction in adults".)

Metabolic factors — A number of electrolyte imbalances can impact weaning from mechanical ventilation [19-25]:

●Hypophosphatemia, hypomagnesemia, and hypocalcemia have been associated with respiratory muscle weakness. Separate studies have demonstrated marked increase in diaphragmatic strength immediately following repletion, suggesting that the deficiencies impair the contractile properties of the diaphragm [19-21].

●Severe hypothyroidism and myxedema impair diaphragmatic function and blunt ventilatory responses to hypercapnia and hypoxia [22-24]. They are uncommon (3 percent), but treatable, causes of weaning failure [25]. In one observational study, nonthyroidal illness syndrome (abnormal thyroid function associated with acute or chronic illness) was an independent risk factor for PMV [26].

The management of hypophosphatemia, hypomagnesemia, hypocalcemia, hypothyroidism, and hyperglycemia are described separately. (See "Hypophosphatemia: Evaluation and treatment" and "Hypomagnesemia: Evaluation and treatment" and "Treatment of hypocalcemia" and "Treatment of primary hypothyroidism in adults" and "Glycemic control in critically ill adult and pediatric patients".)

Sepsis or SIRS — Impaired oxygen uptake is commonly caused by sepsis or systemic inflammatory response syndrome (SIRS) [27]. As a result, anaerobic metabolism increases and metabolic acidosis develops. The need to compensate for the acidemia increases ventilatory demand and impairs weaning. (See "Evaluation and management of suspected sepsis and septic shock in adults".)

Psychological fears — Psychological factors may be among the most important non-respiratory factors leading to ventilator dependence. Stress can be minimized by frequent communication between the staff, patient, and patient's family [28]. Ambulation and environmental stimulation using television, radio, or books improves attitude and long-term outlook [29]. Biofeedback may be helpful in decreasing the weaning time in patients who are having difficulty withdrawing from ventilator support [30,31].

Nutrition — During critical illness, protein catabolism leads to decreased respiratory muscle mass, strength, and endurance [32]. The purpose of nutrition support is to minimize these effects. There are studies that suggest that some nutrition support may enhance the likelihood of weaning success and other positive outcomes, although this is controversial [33-36]. (See "Nutrition support in critically ill patients: An overview".)

It is important that the amount of nutrition support be adequate without being excessive:

●Severe negative energy balances are associated with increased mortality [36]. Moderate caloric levels of caloric intake (33 to 65 percent of American College of Chest Physician recommended targets) have been associated with better clinical outcomes than higher levels of caloric intake [33].

●Overfeeding with excessive carbohydrates can impair ventilator withdrawal [33], presumably by leading to excess carbon dioxide production and an increased ventilatory load on the respiratory muscles.

Physical therapy — Patients who require PMV are frequently deconditioned due to prolonged illness and immobility [37].

●One study randomly assigned 39 patients who required PMV to receive six weeks of physical training or no physical therapy [38]. Compared to baseline, patients who received physical therapy improved their respiratory and extremity muscle strength, functional status, and ventilator-free duration. In contrast, the control group did not improve in any of the outcomes measured.

●Another study documented that early rehabilitation after coronary artery bypass surgery decreased duration of mechanical ventilation and hospital stays [39]. Another study evaluated 80 patients who underwent mechanical ventilation for greater than 72 hours and randomized them to rehabilitation versus no rehabilitation [40]. Rehabilitation was leveled, including anti-gravity limb training at the lowest levels all the way up to sitting in a chair, standing, and walking for the highest levels. Diaphragm function was assessed using ultrasound. After three days of rehabilitation training, all patients had poorer diaphragmatic function than on day 1, indicating negative effects of mechanical ventilation itself on diaphragm function. However, patients undergoing rehabilitation had less decline in diaphragm function than those who did not. Early rehabilitation therapy also shortened the duration of ventilator use and duration of intubation.

While even more data are needed to establish the best protocols for physical therapy in weaning patients who require PMV [41,42], the physical and psychological benefits of physical therapy have already been established in a wide range of patient care settings, and it is reasonable to expect that these benefits extend to patients who require PMV.

Drugs — Medications can have a profound impact on a patient's ability to wean from mechanical ventilation. As an example, many drugs suppress central ventilatory drive (eg, central nervous system depressants like opiates, benzodiazepines, or barbiturates) or induce respiratory muscle weakness (eg, paralytics, corticosteroids). A patient's medications should be reviewed prior to weaning. Medications that might impair weaning should be discontinued or titrated to the minimal effective dose, depending on their importance.

Weaning strategies — Strategies for the weaning and discontinuation of PMV are summarized here. Strategies for the weaning and discontinuation of mechanical ventilation in patients who received mechanical ventilation for a shorter duration are presented elsewhere. (See "Initial weaning strategy in mechanically ventilated adults".)

Guidelines issued by a collective task force organized by the American College of Chest Physicians recommend that weaning be gradual in the patient requiring PMV [43]. The initiation of weaning should be considered when the following criteria are satisfied:

●Evidence for reversal of the underlying cause for respiratory failure

●Adequate oxygenation (eg, PaO2/FiO2 ratio >150 to 200 on ventilator settings that include ≤8 cm H2O of positive end-expiratory pressure (PEEP) and an FiO2 ≤0.5)

●Adequate pH (eg, ≥7.25)

●Hemodynamic stability, defined as the absence of active myocardial ischemia and clinically significant hypotension

●Ability to initiate an inspiratory effort

The optimal protocol for weaning in patients who have required PMV is not known. In a randomized trial specific to patients with PMV, patients who received unassisted breathing trials through a tracheostomy collar had a shorter median time to ventilator liberation (15 days [interquartile range (IQR) 8 to 25 days] versus 19 days [IQR 12 to 31 days]), although 6-month and 12-month mortality did not differ [44]. This trial was conducted in a single long-term weaning facility, and further studies at other institutions are needed to determine the generalizability of these findings.

Several studies suggest that protocols that stress frequent reassessment have a greater impact on weaning than the method [1,45,46]. As an example, an observational study evaluated 252 patients requiring PMV who were weaned via a respiratory therapist-driven protocol [46]. The protocol advanced patients directly to a one-hour spontaneous breathing trial if the rapid shallow breathing index (frequency to tidal volume ratio) was less than 80. Protocol-guided weaning was associated with a shorter median duration of mechanical ventilation compared to historical controls (17 versus 29 days). This suggests that use of a standardized protocol may be more important than the weaning strategy itself. The same investigators later found that a rapid shallow breathing index less than 97 was the most accurate predictor of a successful spontaneous breathing trial in patients with PMV [47].

In our clinical practice, once patients can tolerate spontaneous breathing trials, we gradually increase the duration of the daily spontaneous breathing trials [1]. Criteria used to assess patient tolerance during spontaneous breathing include the respiratory pattern, adequacy of gas exchange, hemodynamic stability, and subjective comfort [43]. Patients who fail spontaneous breathing should be placed on a non-fatiguing, comfortable mode of ventilation and the cause of failure determined and corrected.

COMPLICATIONSPatients receiving PMV suffer similar complications as their counterparts receiving short-term mechanical ventilation. (See "Physiologic and pathophysiologic consequences of mechanical ventilation".)

Studies have identified the following as common problems that occur during PMV: infection (eg, bacterial pneumonia, tracheobronchitis, line sepsis, Clostridium difficile colitis, urosepsis), volume overload, tracheal bleeding, ileus, renal failure, pneumothorax, seizures [48-50]. Laryngeal edema is also common. In a prospective study of 95 patients undergoing PMV (mean duration 28 days), 37 percent had laryngeal edema (defined as a cuff leak <140 mL) when assessed at the time of tracheostomy [51].

Diagnosis of pneumonia in patients undergoing PMV is particularly difficult because the airways of these patients are frequently colonized with bacteria. This was illustrated by a study that performed quantitative bronchoalveolar lavage in 14 asymptomatic patients who required PMV [52]. There was growth of at least one organism at >10,000 CFU/mL (the generally accepted minimum for diagnosis of ventilator-associated pneumonia) in 29 of the 32 lobes sampled. Thus, the utility of quantitative bronchoscopic culture in patients who require PMV is uncertain and requires further study. Until then, clinicians need to rely more heavily on other indicators of infection.

Many patients are transferred from the intensive care unit (ICU) to a long-term acute care (LTAC) facility for PMV and weaning. Although pneumonia is the most common infectious disease in patients that require PMV, little data exists regarding the epidemiology of ventilator-associated pneumonia in LTAC. Anecdotal evidence suggests that the causative microorganisms are initially the same as those prevalent in the ICU of origin and later the flora prevalent in the LTAC [53,54]. (See "Epidemiology, pathogenesis, microbiology, and diagnosis of hospital-acquired and ventilator-associated pneumonia in adults".)

Tracheostomy is another source of complications seen in patients receiving PMV. Examples of tracheostomy complications include loss of airway patency due to unplanned decannulation, fistula formation between the trachea and the innominate artery, and obstruction of the tracheal tube can occur due to mucous plugging or the development of granulation tissue.

OUTCOMESFamily members and caregivers tend to be more optimistic than clinicians about the eventual outcomes. This was demonstrated by an observational study of 126 patients requiring PMV [55]. The study found that family members and caregivers were more likely than clinicians to expect the patient to be alive (94 versus 43 percent), lack major functional limitations (71 versus 6 percent), and have a good quality of life (83 versus 4 percent) one year later.

Estimates of mortality and other clinical outcomes vary considerably for patients undergoing PMV. The variability probably reflects whether the population studied is a general population of patients requiring PMV or a subset of patients selected for their high weaning potential. It may also reflect the transfer practices (from the intensive care unit [ICU] to a long-term acute care [LTAC] facility) of the hospitals studied, as hospitals that more readily transfer patients from the ICU to an LTAC have been shown to have lower mortality rates and shorter lengths of stay [56].

However, overall mortality for these patients is high and, even for the survivors, quality of life is low. It is important that clinicians educate patients and families about these potential outcomes prior to tracheostomy placement and have ongoing discussions with patients regarding overall goals of care. (See 'Assessing patient goals and preferences' above.)

Mortality — Patients undergoing PMV have a high burden of palliative care needs and a high mortality that ranges from 33 to 73 percent [50,57-65]. The high mortality rates in this population were illustrated by the following studies:

●A meta-analysis of 39 studies of patients on PMV reported a one-year mortality of approximately 60 percent (73 percent in US hospitals and 47 percent in non-US hospitals) [64].

●One observational study of 1419 patients on PMV reported a similar one-year mortality of 52 percent [50]. Among these patients, 25 percent died in the weaning hospital and 27 percent died after discharge. Patients were excluded from the study if they were admitted for end-of-life care, terminal weaning, or were deemed incapable of weaning at the time of admission.

●In a smaller study of 80 patients who were admitted to a respiratory care unit for PMV and survived to discharge, 55 percent died within one year after discharge [66]. Poor skin integrity and chronic irreversible neurologic diseases were associated with increased risk for mortality. Survivors of PMV tend to be those who are younger and spent less time in the ICU [67]. However, in another study also focusing on PMV patients admitted to an LTAC, 33 percent died within one year after discharge [65].

●In a Canadian database analysis of hospital admissions between 2002 and 2013, there were 11,600 patients who underwent PMV (PMV >21 days) [68]. When compared with the patients who did not undergo PMV, patients who underwent PMV had a higher in-hospital mortality (42 versus 28 percent), and they were more likely to be discharged to other facilities (85 versus 44 percent). Among the patients who were discharged from the hospital, those who underwent PMV were more likely to die (17 versus 11 percent) and be readmitted to hospital at one year (47 versus 38 percent).

●Another prospective longitudinal study of 315 patients reported a one-year mortality of 33 percent [65].

The use of variables to predict mortality has been evaluated [62,69,70]. The variables included in one prospective study were the need for vasopressors, the need for hemodialysis, the presence of thrombocytopenia, and an age ≥50 years on the 21st day of mechanical ventilation [70]. The absence of these factors was associated with 15 percent mortality, whereas the presence of three or four factors was associated with a mortality of 97 percent. In a database claims study, additional predictors of mortality in those ≥65 years included a do-not-resuscitate order, the presence of comorbidities, admission from or to a skilled-care facility, longer hospital length of stay, principal diagnoses of sepsis and hematologic malignancy, and male sex [62]. In another retrospective study of 866 patients undergoing PMV in a LTAC, a higher burden of chronic comorbid illnesses correlated negatively with survival [71].

Weaning success — Patients requiring PMV spend an average of 36 days mechanically ventilated in the ICU and 31 days weaning outside the ICU [43]. Some patients require several months to be liberated from mechanical ventilation [57]. Unless a patient has respiratory failure due to an irreversible disease process, patients requiring PMV should not be considered permanently ventilator-dependent until at least three months of weaning has failed [43]. Another examined the utility of a score based on mechanical ventilator settings calculated after tracheostomy placement to predict ventilator independence and demonstrated an AUC of 0.71 for differentiating patients who were liberated within 14 days [72].

Several studies report consistent rates of successful weaning, ranging from 47 to 53 percent [64,65,73,74]. In a meta-analysis of 39 studies of patients on PMV only 50 percent were successfully liberated from mechanical ventilation [64]. Similarly, a retrospective cohort study of 135 patients admitted to an LTAC facility for weaning reported that 43 percent were successfully weaned and the remaining 58 percent were fully or partly dependent upon mechanical ventilation at one year [73]. Among those who were successfully liberated from mechanical ventilation, the majority (81 percent) were decannulated successfully. In general, the longer the ventilator-free period, the lower the likelihood of need for PMV reinstitution [74].

Discharge home — In a meta-analysis of 39 studies of patients on PMV only 19 percent of patients (range 16 to 24 percent) were discharged to home [64]. In an observational study of 80 patients requiring PMV (defined in this study as ≥7 days of mechanical ventilation), the proportion of patients who were home, institutionalized, and deceased at six months were 47, 14, and 39 percent, respectively [75]. Three or fewer comorbid conditions and an Acute Physiology Score ≤21 were associated with the best outcomes. In contrast, patients with more comorbid conditions or a slower rate of improvement were least likely to be discharged home within six months.

Quality of life — Survivors of critical illness have a lower quality-of-life (QOL) than age- and sex-matched controls, particularly patients who require PMV or survive acute respiratory distress syndrome (ARDS), trauma, or sepsis [76]. However, QOL tends to improve over years.

While mortality rates are high, it appears that certain patients are able to regain substantial function. An observational study of 718 patients who required 14 or more days of mechanical ventilation in the ICU revealed that 99 percent of three-year survivors were independent and living at home [77]. Only 50 percent reported mild to moderate functional impairment. Another study examined 25 patients discharged from a ventilator rehabilitation unit and demonstrated that PMV had no independent adverse effect on QOL several years later [78]. QOL instead appeared to be related to the presence or absence of chronic underlying diseases.

ARDS survivors who require PMV have poorer QOL than other ARDS survivors. In a study of 74 patient with ARDS who required PMV (mean duration of ventilation 28 days), neurocognitive sequelae were detected in 77 percent of survivors at discharge and 47 percent of survivors two years later [79]. In addition, 25 percent of patients reported moderate to severe depression and anxiety two years after discharge.

Approximately 76 percent of patients who survive PMV and tracheostomy indicate that they would have chosen mechanical ventilation if they were able to make the decision [80]. But, the responses are influenced by their current health, as well as the financial and emotional burden that their illness had on their family.

Neuropsychological and physical — Survivors of critical illness commonly experience neurocognitive and psychological dysfunction. Data from prospective observational cohorts of patients who survive ICU admission suggest that the populations at risk are older patients and those with acute respiratory distress syndrome and sepsis [81-85].

Psychologic dysfunction has also been noted in populations that have undergone PMV that are transferred to LTAC facilities for ventilator weaning. In a prospective cohort study of 336 patients transferred to a LTAC facility for PMV, 42 percent were diagnosed with depressive disorders [86]. These patients were at higher risk for weaning failure and mortality. In a similar study with 41 patients, 12 percent were diagnosed with post-traumatic stress disorder within three months following weaning [87].

Long-term cognitive impairment has been associated with the presence, severity, and duration of associated delirium in survivors of critical illness [88]. Critical illness has also been identified as a potential risk factor for dementia. These issues are discussed in detail separately. (See "Delirium and acute confusional states: Prevention, treatment, and prognosis", section on 'Outcomes' and "Risk factors for cognitive decline and dementia".)

Critical care neuromyopathy is common after critical illness, the details of which are discussed separately. (See "Neuromuscular weakness related to critical illness" and "Post-intensive care syndrome (PICS)", section on 'Physical impairment'.)

Resource utilization — There is a growing body of literature examining the costs of caring for patients who require PMV. One cost-effectiveness analysis found that providing PMV costs $55,460 per life-year gained and $82,411 per quality-adjusted life-year gained, compared to withdrawal of ventilation [89]. The incremental costs per quality-adjusted life-year gained exceeded $100,000 among those patients who were ≥68 years old or whose predicted one year mortality was >50 percent. (See "A short primer on cost-effectiveness analysis".)

Much of this cost is probably related to the cost of ongoing and recurrent medical care. This was suggested by a prospective cohort study that followed patients who required PMV for one year following discharge from the acute care hospital [90]. Sixty-seven percent of patients required at least one readmission to an acute care hospital, 74 percent of days alive were spent in a health care facility or receiving home health care, and 91 percent of patients had some functional dependency at the end of the study. The mean cost per patient exceeded $300,000.

TRANSFER FROM ICUPatients requiring PMV were historically cared for in the intensive care unit (ICU). In the 1990s, changes in reimbursement created incentives to transfer patients undergoing PMV from the ICU of acute care hospitals to long-term assisted care (LTAC) facilities. Many patients requiring PMV undergo weaning and discontinuation of mechanical ventilation in an LTAC. The selection of patients for transfer from an ICU to an LTAC is discussed separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit".)

SUMMARY AND RECOMMENDATIONS

●Prolonged mechanical ventilation (PMV) is defined by the Centers for Medicare and Medicaid Services in the United States as greater than 21 days of mechanical ventilation for at least six hours per day, although many studies have used an alternative duration to define PMV. (See 'Introduction' above.)

●There are no variables that reliably identify patients who will require PMV. (See 'Predictors' above.)

●No mode of ventilation has proven superior to others in achieving liberation from mechanical ventilation. (See 'Weaning strategies' above.)

●The most common complications of PMV are related to infections or tracheostomy. (See 'Complications' above.)

●Mortality is high among patients that require PMV, although a subgroup of patients will return to independent living with satisfactory function. (See 'Outcomes' above.)

●Patients requiring PMV should not be considered permanently ventilator dependent until three months of weaning attempts have failed. (See 'Weaning strategies' above and 'Outcomes' above.)

●For patients who are facing possible tracheostomy and long-term ventilator dependence, a meeting with the patient is essential to review their goals and preferences in the context of their expected prognosis and quality of life. If the patient is not able to participate in decision making, we meet with their designated decision-maker, or in the absence of a patient designated decision-maker, with the patient’s family. (See 'Assessing patient goals and preferences' above.)

●We suggest that potential causes of ventilator dependence be optimized prior to the initiation of weaning from PMV, rather than weaning while the causes are being corrected (Grade 2C). (See 'Optimization for weaning' above.)

●We suggest that weaning be initiated once the following criteria are satisfied (Grade 2C):

•Evidence for some reversal of the underlying cause for respiratory failure

•Adequate oxygenation (eg, PaO2/FiO2 ratio >150 to 200 on ventilator settings that include ≤8 cm H2O of positive end-expiratory pressure and an FiO2 ≤0.5)

•Adequate pH (eg, ≥7.25)

•Hemodynamic stability, defined as the absence of active myocardial ischemia and clinically significant hypotension

•Capable of initiating an inspiratory effort

●We suggest that patients requiring PMV be weaned by gradually increasing the duration of spontaneous breathing (Grade 2C). (See 'Weaning strategies' above.)

●Patients who fail spontaneous breathing should be placed on a non-fatiguing, comfortable mode of ventilation and the cause of failure determined and corrected. We suggest that daily spontaneous breathing resume after the cause of failure has been corrected (Grade 2C). (See 'Optimization for weaning' above.)

ACKNOWLEDGMENTThe UpToDate editorial staff acknowledges Melissa Miller, MD, who contributed to an earlier version of this topic review.

Use of UpToDate is subject to the Terms of Use.

REFERENCES

WEANING AND DISCONTINUATION OF MECHANICAL VENTILATION

As the need for critical care services and emergency department lengths of stay increase, emergency clinicians will increasingly be called upon to provide long-term critical care management, including weaning and discontinuation of mechanical ventilation [24,25].

Weaning is the process whereby mechanical ventilatory support is gradually withdrawn and the patient resumes spontaneous breathing. Weaning can be separated into two parts: weaning to partial ventilator support, and weaning to discontinuation of support and removal of the endotracheal tube. Aspects of weaning of particular import to the emergency clinician are described below. Weaning from mechanical ventilation is discussed in detail elsewhere. (See "Weaning from mechanical ventilation: Readiness testing" and "Initial weaning strategy in mechanically ventilated adults" and "Management of the difficult-to-wean adult patient in the intensive care unit".)

Before beginning a weaning trial, clinicians should determine whether the patient is ready using the following criteria as a general guide [26,27]:

●Evidence for some reversal of the underlying cause of respiratory failure

●Adequate oxygenation (PaO2 >60 mmHg on FiO2 <0.4; PEEPe <10 cmH2O; PaO2/FiO2 >150 to 300)

●Stable cardiovascular status (HR <140; stable BP; no, or minimal, use of vasopressors)

●No significant respiratory acidosis (pH ≥7.25)

●Adequate hemoglobin (generally Hgb >7 g/dL in patients without ischemic cardiac disease, or Hgb >10 in patients with ischemic cardiac disease)

●Adequate mentation (arousable; can follow commands reliably; no continuous sedative infusions)

●Stable metabolic status (acceptable electrolyte levels)

Clinicians should adapt these criteria to clinical circumstances; some patients will not satisfy all criteria yet be successfully weaned off mechanical ventilation. Over the years, a wide variety of physiologic indices have been proposed to assist in the discontinuation of ventilatory support. Such indices have varying strengths and weaknesses, and different applications. Variables such as respiratory rate, PaO2/FiO2 (P/F) ratio, and the rapid shallow breathing index (RSBI) are used.

RSBI is a commonly used assessment tool to determine readiness to wean and discontinue mechanical ventilation in the ICU. The RSBI measurement consists of a one-minute trial of unassisted breathing with an extrinsic positive end-expiratory pressure (PEEPe) of 0 cmH20 and pressure support of 0 cmH2O. At the end of one minute, the average respiratory rate is divided by the average tidal volume (VT) to obtain the RSBI (ie, RSBI = RR/VT). A number less than or equal to 105 has been found to be most predictive of successful extubation. (See "Weaning from mechanical ventilation: Readiness testing".)

After an initial assessment of weaning, including calculation of a RSBI, we perform a spontaneous breathing trial (SBT) to determine if the patient is prepared for discontinuation of mechanical ventilation. There are three ways to perform an SBT: putting the patient on minimal pressure support and PEEPe, assessing respiratory parameters (so-called "performing mechanics"); using continuous positive airway pressure (CPAP) alone; or using a T-piece trial, which requires the patient to breathe through the endotracheal tube for a preset period of time with oxygen but without ventilatory support. Institutional approaches vary, but any of the methods described is acceptable. (See "Initial weaning strategy in mechanically ventilated adults".)

The criteria used to assess patient tolerance during an SBT are the respiratory pattern, adequacy of gas exchange, hemodynamic stability, and patient comfort. Generally, if the patient tolerates an SBT lasting 30 minutes, the mechanical ventilator should be discontinued and the endotracheal tube removed. A longer SBT (up to 120 minutes) may be necessary if the patient's condition is more uncertain.

Otherwise healthy patients intubated for a transient problem (eg, acute drug intoxication) can often be extubated rapidly following a brief period of observation. Once the problem has resolved and the patient is awake, breathing spontaneously, and manifesting no signs of respiratory or hemodynamic instability, the endotracheal tube can be removed.

SUMMARY AND RECOMMENDATIONS

●Mechanical ventilation is performed in the emergency department (ED) to accomplish any of a number of goals, including the following:

•To protect the airway

•To improve pulmonary gas exchange (ie, reverse hypoxemia or acute respiratory acidosis)

•To relieve respiratory distress (ie, decrease oxygen consumption or respiratory muscle fatigue)

•To permit appropriate sedation and neuromuscular blockade

●To perform mechanical ventilation properly, emergency clinicians must be familiar with ventilator settings, modes of ventilation, and potential complications. Potential complications include diminished cardiac output, ventilator associated lung injury, and pneumonia. Ventilator management and additional complications are described in the text. (See 'Ventilator settings' above and 'Modes of ventilation' above and 'Complications' above.)

●There is no single optimal mode of mechanical ventilation; diseases and patient condition vary over time and ventilator settings must be adjusted accordingly. Nevertheless, certain guiding principles should be applied in most instances, including:

•Minimize plateau pressures and tidal volumes, allowing hypercapnia if necessary (except in brain-injured patients), to reduce the risk of lung injury.

•Optimize extrinsic positive end-expiratory pressure (PEEPe) to prevent alveolar collapse and improve oxygenation.

•Reduce inspired oxygen to nontoxic levels (≤60 percent) as quickly as possible.

●Emergency clinicians can select among three fundamental strategies for mechanical ventilation: noninvasive positive pressure ventilation (NPPV), general invasive positive pressure ventilation (IPPV), and lung-protective invasive positive pressure ventilation (L-IPPV). NPPV has proven most effective in patients with acute exacerbations of chronic obstructive pulmonary disease and acute cardiogenic pulmonary edema. L-IPPV is the strategy used to prevent ventilator-associated lung injury, including barotrauma. Each approach, including initial ventilator settings, is described in the text. (See 'Approach to ventilatory management' above.)

●To improve patient outcomes, modifications to mechanical ventilation must be made based upon the disease process. Approaches to ventilator management for important conditions that confront the emergency clinician are provided in the text. (See 'Disease-specific ventilatory management' above.)

●Emergency clinicians should not reflexively treat the "bucking," distressed patient, presumed to be "fighting" the ventilator, with neuromuscular blocking agents and sedative medications. To do so is to risk missing potentially life-threatening problems, such as a tension pneumothorax. Approach the distressed mechanically ventilated patient in a systematic fashion, as outlined in the attached algorithm (algorithm 1). (See 'Approach to ventilated patient in distress' above.)

●Once organic causes of distress are addressed, clinicians must ensure that the intubated patient receives adequate sedation and analgesia. The Society of Critical Care Medicine's algorithm for sedation and analgesia of mechanically ventilated patients provides a reasonable approach. We have modified the original version for use in the ED(algorithm 3). (See 'Sedation and analgesia for the ventilated patient' above.)

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Initial weaning strategy in mechanically ventilated adults

Authors: Scott K Epstein, MD; Allan Walkey, MD, MSc
Section Editor: Polly E Parsons, MD
Deputy Editor: Geraldine Finlay, MD

Contributor Disclosures

All topics are updated as new evidence becomes available and our peer review process is complete.

Literature review current through: Apr 2022. | This topic last updated: Apr 06, 2021.

INTRODUCTIONLiberation from mechanical ventilation is an important process in recovery of critically ill patients in the intensive care unit. It is a three-step process, consisting of readiness testing, weaning, and extubation. Patients who wean successfully have less morbidity and mortality and use fewer resources than patients who require prolonged mechanical ventilation [1-4]. Thus, ensuring that patients wean in a safe and effective way is important for patient outcomes.

The practice of weaning varies widely. Our approach to initial weaning methods is reviewed here. Assessment of a patient's readiness to wean, extubation, and management of the difficult to wean patient are described separately. (See "Weaning from mechanical ventilation: Readiness testing" and "Extubation management in the adult intensive care unit" and "Management of the difficult-to-wean adult patient in the intensive care unit".)

DEFINITIONS

Readiness testing — Readiness testing uses clinical criteria (and occasionally physiological tests) to determine whether a patient is ready to begin weaning from mechanical ventilation (table 1). (See "Weaning from mechanical ventilation: Readiness testing".)

Weaning — Weaning is the process of decreasing the degree of ventilator support and allowing the patient to assume a greater proportion of their own ventilation (eg, spontaneous breathing trials or a gradual reduction in ventilator support). The purpose is to assess the probability that mechanical ventilation can be successfully discontinued. (See "Extubation management in the adult intensive care unit".)

●Simple wean – Patients are considered to have undergone a simple wean when they pass their first weaning trial, typically a spontaneous breathing trial (SBT). This is the subject of this topic review.

●Difficult-to-wean – Patients are considered difficult-to-wean if they fail their first SBT and then require up to three SBTs or seven days to pass an SBT [5]. This population is discussed separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit".)

●Prolonged weaning – Patients are considered to have undergone prolonged weaning if they fail at least three SBTs or require more than seven days to pass an SBT. (See "Management and prognosis of patients requiring prolonged mechanical ventilation".)

Extubation — Extubation is the removal of the endotracheal tube (ETT) and is the final step in liberation from mechanical ventilation support. (See "Extubation management in the adult intensive care unit".)

CHOOSING A WEANING METHODFor patients who have been intubated for more than 24 hours and have been deemed as ready to wean (see "Weaning from mechanical ventilation: Readiness testing"), we suggest a weaning trial. Patients who are intubated for less than 24 hours do not necessarily need to undergo a weaning trial (eg, patients who undergo short-term intubation for airway protection or minor surgery).

●Daily spontaneous breathing trials (SBTs) with inspiratory pressure support is our preferred method of weaning based upon randomized trials that have shown it is efficient, safe, and effective [6-8]. However, practice varies widely. (See 'Daily spontaneous breathing trials (SBTs)' below and 'Variation in practice' below.)

●Older methods include progressive decreases in the level of pressure support during pressure support ventilation (PSV) and progressive decreases in the number of ventilator-assisted breaths during intermittent mandatory ventilation (IMV). (See 'Alternative methods' below.)

●Newer weaning methods include computer-driven automated PSV weaning and early extubation with immediate use of postextubation noninvasive ventilation (NIV). (See 'Selecting manual or automated weaning' below and 'Extubation to noninvasive ventilation' below.)

Selecting manual or automated weaning — Weaning protocols can be manual (ie, personnel-driven) or automated (ie, computer-driven) [8-16]. There is insufficient evidence to definitively conclude that one method is superior to the other. We generally prefer manual protocols because they can be tailored to the patient, they are less costly, and because most of the available clinical trials that demonstrated efficacy used manual protocols [11,12]. While automated systems are less labor-intensive, there are fewer clinical trial data supporting their efficacy.

●Manual protocols – A manual system is one where, following a daily assessment of readiness to wean, healthcare staff manually alter the ventilator settings so that the patient undergoes a weaning trial. Such protocols are usually respiratory therapy- or nursing-driven. While effective, manual protocols are labor-intensive and compliance can be challenging, especially in a busy environment [13,17,18].

●Automated systems – Automated systems use proprietary, computerized, closed loop weaning software packages that automate weaning by pressure support. Once the patient is deemed ready for weaning by healthcare staff, the automated weaning program adjusts levels of pressure support during the weaning trial to keep the patient in a normal range of intermittently-monitored respiratory rate, tidal volume, and exhaled carbon dioxide. Once the patient is stable at a specific level of pressure support, the program automatically reduces the pressure support level and reassesses respiratory stability.

Some patients may not be suitable for automated weaning. For example, patients whose baseline arterial carbon dioxide tension (PaCO₂) is >60 mmHg should not be weaned by automated systems, since a PaCO₂ >60 mmHg is the upper limit of the target range in most weaning software packages. In addition, automated systems are generally not necessary in the postoperative setting when extubation is expected within a short period of time (eg, one to two days) following surgery.

●Evidence supporting protocolized weaning – The efficacy of ventilator liberation protocols is supported by numerous clinical trials and meta-analyses comparing protocolized weaning versus no protocol (ie, physician judgment) [11,12]. In a meta-analysis of 14 trials (2205 patients), protocolized weaning reduced mechanical ventilation (MV) duration by 26 percent (95% CI 13 to 37 percent), which corresponds to a reduction of approximately 25 hours (95% CI 12 to 36 hours) assuming an average MV duration of 96 hours without protocolized weaning [12]. Intensive care unit (ICU) length of stay was reduced by 11 percent (95% CI 3 to 19 percent), which corresponds to a reduction of approximately one day (95% CI 0.2 to 1.5 days), assuming an average ICU length of stay of eight days without protocolized weaning. Both groups had similar mortality rates (22 percent each) and reintubation rates (9.4 percent in the protocolized weaning group versus 11.9 percent in the control group). The clinical trials included in the meta-analysis were heterogeneous with regard to the population studied and protocol used. Most protocols were driven by nursing and respiratory therapy staff and included a daily assessment of readiness to wean, followed by a weaning trial if deemed ready. The effect on reducing MV duration did not appear to differ in trials using manual weaning protocols compared with computer-driven approaches; however, only two trials (n=154) used computer-driven protocols, which limits the conclusions that can be drawn from this subgroup analysis. The relative effect size appeared to differ according to type of ICU, with larger effect size in patients admitted to surgical ICUs (47 percent reduction in MV duration [95% CI 20 to 65 percent]), medical ICUs (29 percent reduction [95% CI 7 to 46 percent]), and mixed ICUs (21 percent reduction [95% CI 2 to 36 percent]); and little to no effect in patients admitted to neurointensive care units (1 percent reduction in MV duration [95% CI 20 percent decrease to 18 percent increase]).

●Comparison of automated versus manual protocols – Small randomized trials comparing computer-driven automated weaning systems with non-automated weaning have reached variable conclusions [10,19-22]. In a meta-analysis of 7 randomized trials (516 patients), patients managed with computer-driven automated systems had shorter MV duration compared with patients in the control group (mean difference one day; 95% CI 0.09-1.9 days) [23]. Mortality and hospital length of stay were similar in both groups. Two other meta-analyses reported similar findings [19,22]. An important limitation of these meta-analyses is that the control group in many of the trials consisted of “usual care” without a standardized weaning protocol. In the one trial that directly compared automated weaning with a standardized non-computer-driven weaning protocol, MV duration was similar in both groups (10.5 versus 11 days, respectively) [10]. In addition, most trials included in the meta-analyses evaluated one specific proprietary system and the findings may not be generalizable to other systems.

Daily spontaneous breathing trials (SBTs) — For most patients with acute respiratory failure on mechanical ventilation, we suggest an SBT as the initial weaning strategy. In an SBT, the patient breaths spontaneously through the endotracheal tube (ETT) for a set period of time, typically 30 minutes to two hours. The amount of ventilator support used for the SBT and the duration are discussed below. (See 'Choosing ventilatory support' below and 'Trial duration' below.)

Approximately 50 to 75 percent of patients pass the initial SBT and are able to be successfully extubated [7,14,24]. For patients who fail the initial SBT, we suggest ongoing weaning with daily SBTs rather than other weaning strategies such as gradual PSV or IMV weaning. A strategy of extubation with immediate application of NIV may be an option for select patients who fail the initial SBT and are at high risk of having further difficulty weaning and extubating (eg, patients with chronic obstructive pulmonary disease [COPD] or chronic hypercapnic respiratory failure). (See 'Alternative methods' below.)

Evidence supporting daily SBTs — The practice of performing daily SBTs is supported by randomized controlled trials and meta-analyses [7,8,12]:

●SBT versus usual care – The available evidence suggests that compared with usual care (ie, weaning at the discretion of the attending physician), performing daily SBTs reduces MV duration. In a meta-analysis of eight trials (1188 patients), protocolized weaning with daily SBTs reduced MV duration by 16 percent (95% CI 0 to 30 percent), which corresponds to a reduction of approximately 15 hours (95% CI 0 to 29 hours) assuming an average MV duration of 96 hours without daily SBTs [12].

●SBT versus other weaning strategies – Based on the available evidence, it is unclear if weaning with daily SBTs is superior to other protocolized weaning strategies such as gradual PSV or IMV weaning. The previously described meta-analysis provided an indirect comparison of SBT-based weaning protocols versus gradual PSV or IMV weaning protocols and did not detect a significant difference between the two approaches; both were more effective than usual care with similar effect sizes [12]. Two small randomized trials have directly addressed this question and reached different conclusions. One trial found that patients weaned with daily SBTs (using T-piece (figure 1)) were successfully extubated sooner than patients who underwent gradual PSV or IMV weaning [7]. The second trial found that patients who underwent gradual PSV weaning had a shorter weaning duration and higher likelihood of successful extubation compared with patients who underwent daily T-piece SBTs or gradual synchronized intermittent mandatory ventilation (SIMV) weaning [14].

The conflicting findings of the two trials may be related to differences in how the SBTs were performed in each trial. In the first trial, patients were extubated if they tolerated a two-hour SBT [7]. The patients were unlikely to develop respiratory muscle fatigue because they were closely monitored and returned to full ventilatory support at the first sign of distress. In contrast, in the second trial, clinicians could request up to three separate SBTs over a 24 hour period, each lasting two hours, before deciding whether to extubate a patient [14]. It is possible that these very prolonged SBTs using a T-piece resulted in fatigue, a process that can take 24 or more hours to reverse (figure 2) [25]. In other words, respiratory fatigue may have slowed the progress of patients weaned via SBTs in the second trial.

One reason why IMV weaning may be less successful than SBT or PSV weaning is that the degree of respiratory muscle rest on IMV is not proportional to the level of ventilatory support and patient is only supported on mandatory breaths [26]. This effect can be overcome by adding PSV to the unsupported breaths during SIMV [27].

Choosing ventilatory support — We suggest performing the SBT with some form of ventilatory support (eg, low-level PSV, automatic tube compensation [ATC] or continuous positive airway pressure [CPAP; eg, 5 cm H₂O]) rather than no ventilatory support (eg, using a T-piece (figure 1)). Choosing among the options for ventilator support is often institution- or clinician-dependent. In our practice, we typically use PSV (eg, inspiratory pressure augmentation of 5 to 8 cm H₂O), which is consistent with the recommendations of the American College of Chest Physicians/American Thoracic Society [28-30]. When using PSV-SBT, the positive end-expiratory pressure (PEEP) remains at 5 cm H₂O and the fraction of inspired oxygen (FiO₂) at 0.4 or lower.

Our approach is based on the rationale that PSV mitigates any increased work of breathing due to resistance of the ETT [26,27,31-34]. This is especially important for patients with small ETTs (eg, size ≤7 mm), but even larger ETTs can have considerable narrowing of the lumen after intubation [32]. In addition, using PSV, ATC, or CPAP during the SBT allows the ventilator's monitoring system and alarms to alert the clinician if there are changes in the patient’s respiratory rate, tidal volumes, or minute ventilation; whereas such monitoring is not possible if a T-piece is used (figure 1). The practice of performing the SBT on PSV is supported by several clinical trials (described below) that suggest PSV-SBT leads to higher rates of successful extubation compared with other methods [30].

Ventilatory support in the form of CPAP in patients at risk for acute cardiogenic pulmonary edema and patients with acute hypercapnia from obstructive lung disease may result in a falsely reassuring SBT, since CPAP is a form of therapy and reduces the work of breathing for both of these conditions, especially in COPD patients with intrinsic positive end expiratory pressure (PEEPi) [35-38]. A T-piece may be more appropriate in such conditions particularly when patients fail an initial PSV-SBT. Ventilatory support with ATC is not used frequently and its use may be institution-dependent.

The evidence supporting the use of PSV-SBT comes from several randomized trials and a meta-analysis [28,30]. The largest trial included 1153 patients who were deemed ready for weaning and were then randomized to a 30-minute trial on PSV (8 cm H₂O) or a two-hour T-piece trial [30]. More patients in the PSV-SBT arm achieved successful extubation at 72 hours compared with those in the T-piece arm (82 versus 74 percent). In addition, 90-day mortality was lower in the PSV-SBT group (13 versus 17 percent; hazard ratio 0.74, 95% CI 0.55-0.99). Reintubation rates and hospital length of stay were similar in both groups. The findings were consistent across various subgroups, including older patients (>70 years), those ventilated for longer than four days, medical and surgical patients, and those with COPD. However, more patients in the PSV-SBT group received some form of noninvasive support (ie, high flow oxygen delivered via nasal cannulae [HFNC] or NIV) following extubation (25 versus 19 percent), which may have contributed to the higher extubation success rate in that group.

In an earlier meta-analysis of four randomized trials (875 patients), not including the trial described above, PSV-SBT compared with T-piece resulted in a higher rate of successful extubation (74 versus 67 percent) [28]. The effect on ICU mortality was not statistically significant (9 versus 12 percent; relative risk 0.74, 95% CI 0.45-1.24); however, only two trials reported this outcome and the meta-analysis may have been underpowered to detect a difference.

Data also suggest that PSV is superior to T-piece trials in patients at high risk of extubation failure. In a study of over 500 patients considered to be at risk of extubation failure, the proportion of successful extubations was higher in patients who underwent a PSV trial compared with T-tube trial (67 versus 56 percent) [39].

Smaller trials comparing SBTs performed with T-piece versus other forms of ventilatory support, including CPAP [40] and ATC [41], did not detect significant differences in extubation success rates.

A single small trial compared ATC with CPAP during the SBT and found a higher rate of extubation success with ATC (82 versus 65 percent) [42]. Another trial comparing ATC with PSV, found similar extubation success rates and reintubation rates in both groups [43].

Trial duration — We typically perform SBTs for a duration of 30 minutes to two hours, which is the range used in most of the available clinical trials. However, the optimal duration for an SBT is uncertain and it may depend upon the underlying reason for intubation, the duration of MV prior to the weaning trial, performance on previous SBTs, and physician- or institution-specific practices.

Our general approach is as follows:

●Duration of MV <24 hours – Some patients who are intubated for <24 hours generally do not require an SBT, although a 30-minute SBT is unlikely to be harmful (eg, following surgery or for airway protection).

●Duration of MV 1 to <10 days – In most patients who have been mechanically ventilated for <10 days, an initial SBT of 30 minutes duration is generally sufficient to determine whether mechanical ventilation can be discontinued [30,44,45]. In a multicenter trial of 526 patients receiving mechanical ventilation (most were intubated for <10 days) randomly assigned to 30-minute or 120-minute T-piece SBTs, rates of weaning failure and reintubation were virtually identical in both groups [44].

●Duration of MV ≥10 days – For patients who are mechanically ventilated for more prolonged periods (eg, ≥10 days), trials of 30 minutes may still be sufficient [30,46]. However, we prefer an individualized approach and in many cases extend trials for up to two hours in this population. For example, patients with chronic respiratory failure who have undergone an extended duration of mechanical ventilation may warrant a longer SBT to ensure that they are ready for extubation. In one study of 75 patients with chronic obstructive pulmonary disease who were mechanically ventilated for 15 or more days, the median time to SBT failure was 120 minutes [45].

●Subsequent SBTs after failed initial SBT – For patients who fail their initial SBT, we generally extend subsequent trials for longer than 30 minutes, up to two hours [45,47]. (See 'Weaning failure' below and "Management of the difficult-to-wean adult patient in the intensive care unit", section on 'Resuming weaning trials'.)

Alternative methods — Older methods of weaning are infrequently used as an initial weaning strategy [6,48]. These include progressive decreases in the level of pressure support during pressure support ventilation (PSV-weaning) and progressive decreases in the number of ventilator-assisted breaths during intermittent mandatory ventilation (IMV-weaning) [7,14]. These methods have largely been supplanted by SBT since data support a shorter duration of MV with SBT weaning when compared with PSV/IMV weaning. These data are discussed above. (See 'Daily spontaneous breathing trials (SBTs)' above.)

Pressure support weaning — There are several protocols that have been used for PSV weaning. As an example, pressure support may be initially set between 12 and 18 cm H₂O (to target a spontaneous respiratory rate ≤25 breaths per minute). PSV is then reduced, if possible, by 2 to 4 cm H₂O at least twice a day until a pressure support of 5 to 8 cm H₂O is reached for two hours or more (ie, typically over a 24 hour period). More rapid reductions in PSV weaning have also been described. PEEP of up to 4 or 5 cm H₂O is usually applied.

As previously discussed, the available clinical trial data suggest that PSV weaning protocols are effective in reducing MV duration compared with usual care (ie, weaning at the discretion of the attending physician). However, the data are conflicting as to whether PSV weaning has similar efficacy, superior efficacy, or inferior efficacy compared with daily SBTs. (See 'Evidence supporting daily SBTs' above.)

Intermittent mandatory ventilation — Several protocols have been used for intermittent mandatory ventilation (IMV) weaning. As an example, the ventilator rate may be initially set at 8 to 12 breaths per minute. The IMV rates is then decreased usually by 2 to 4 breaths per minute, if possible, at least twice a day until four or five breaths per minute or less is reached for two hours or more.

As previously discussed, the available clinical trial data suggest that IMV weaning protocols are effective in reducing MV duration compared with usual care (ie, weaning at the discretion of the attending physician). However, the data suggest that IMV weaning is not superior to daily SBTs, and may in fact be inferior. (See 'Evidence supporting daily SBTs' above.)

Extubation to noninvasive ventilation — In patients deemed ready to wean, a strategy of extubation with immediate application of NIV has been proposed as an option for select patients who fail the initial SBT (eg, patients with COPD or chronic hypercapnic respiratory failure). Extubation to NIV can also be used as a tool in patients at high risk of extubation failure. These issues are described separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit", section on 'Method of weaning trial' and "Extubation management in the adult intensive care unit", section on 'Noninvasive ventilation'.)

Variation in practice — Weaning practice varies significantly among clinicians, hospitals, regions, and countries. Our preferred weaning method is consistent with observed practice in most US ICUs as illustrated in a multicenter, international prospective observational study of 1868 patients who were mechanically ventilated for at least 24 hours and admitted to one of 142 intensive care units (ICUs) in six geographic regions (Canada, US, UK, Europe, India, Australia/New Zealand) [49]. Most ICUs had a university affiliation and were medical surgical ICUs or multidisciplinary ICUs. The results were as follows:

●Written directives to screen for SBT readiness varied widely, ranging from 5 to 83 percent. Written directives for screening were present in more than half of participating ICUs in Canada, India, and the US (83 percent) while written directives for SBT conduct were lower, though present in 78 percent of US ICUs. Similarly, the frequency of screening (eg, never, once daily, twice daily) and personnel involved (eg, nursing, respiratory therapist, clinician) also varied among regions; daily screening was conducted in 83 percent of US ICUs. Readiness testing is discussed separately. (See "Weaning from mechanical ventilation: Readiness testing".)

●Approximately 20 percent of patients died prior to a weaning attempt and 8 percent underwent a direct tracheostomy. Among the remaining patients, over two-thirds underwent an SBT while the remaining third were directly extubated without an SBT. ICUs in the US were associated with greater odds of using an SBT compared with ICUs in other regions. Most regions outside the US were using pressure support mode before an SBT or direct extubation, while most ICUs in the US were receiving volume- or pressure-controlled modes of ventilation.

●Among those who underwent an SBT, almost half used low-level pressure support (PSV) with positive end expiratory pressure (PEEP), while one quarter used a T-piece, and 11 percent used continuous positive airway pressure (CPAP). PSV with PEEP was more commonly used in all regions except India and Europe, where T-piece trials were the most common method used.

ASSESSMENT OF WEANING SUCCESS OR FAILURERegardless of the weaning strategy used, the clinician must determine whether weaning was a success or failure so that a decision for extubation can be made.

Clinical assessment — During the weaning trial, clinicians should monitor vital signs and ventilator parameters such as the tidal volume and respiratory rate (ie, minute ventilation). In addition, patients should be assessed for respiratory distress and mental status changes, and if alert and responsive, asked about the presence of dyspnea and chest pain. Telemetry monitors should also be examined for ST changes that might prompt electrocardiography to look for cardiac ischemia. At the end of the spontaneous breathing trial (SBT), an arterial or venous blood gas (ABG, VBG) is not always necessary. However, blood gas analysis is prudent in those at risk of developing acute hypercapnia during weaning (eg, patients with chronic obstructive pulmonary disease [COPD], patients who underwent prolonged mechanical ventilation, patients with known or suspected neuromuscular weakness).

Importantly, clinicians should use their clinical judgement at the bedside to make a final conclusion regarding success or failure. Nonetheless, several objective criteria were used during weaning trials to indicate failure. The development of one or more of these criteria listed in the table (table 2) generally indicates weaning failure [7,14].

While fever can contribute to weaning failure by inducing tachycardia and respiratory distress, it is not necessarily a criterion per se for designating the trial as a failure.

Weaning success — When a patient successfully passes a weaning trial, they should be evaluated for safety of extubation. This requires an assessment of the volume of respiratory secretions as well as airway patency and protection (ie, has a sufficient cough and adequate level of consciousness). Extubation is reviewed in detail separately. (See "Extubation management in the adult intensive care unit".)

For patients who successfully pass an SBT on low-level pressure support ventilation (PSV; eg, 7 cm H₂O), it is not necessary to “rest” the patient by resuming prior ventilatory settings prior to extubation. However, if the SBT is performed on T-piece (figure 1), there may be a role for “resting” prior to extubation [50].

Weaning failure — In general, patients who fail a weaning trial should be placed back on their previous ventilator settings. No further attempts at weaning are typically made for another 24 hours, although rare exceptions can be made. For example, it is reasonable to repeat the weaning trial sooner in patients who have sedation-related failure (ie, hypoventilation from excessive somnolence) if they are subsequently more alert after weaning sedation.

Causes of weaning failure should be sought and treated, if feasible, before resuming further weaning trials (table 3). Management of patients who fail their initial SBT is discussed in detail separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit".)

SOCIETY GUIDELINE LINKSLinks to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Weaning from mechanical ventilation".)

SUMMARY AND RECOMMENDATIONS

●Liberation from mechanical ventilation is a three-step process, consisting of readiness testing, weaning, and extubation. Weaning is the process of decreasing the amount of support that the patient receives from the mechanical ventilator, so the patient assumes a greater proportion of the ventilatory effort. The purpose is to assess the probability that mechanical ventilation can be successfully discontinued. (See 'Introduction' above.)

●Initial approach to weaning – Practice varies widely. The steps below represent our approach to initial weaning in patients who have been intubated for more than 24 hours and have been deemed as ready to wean:

•We recommend protocolized weaning rather than no protocol (ie, physician judgment) (Grade 1B). For most patients, we suggest manual weaning protocols (ie, personnel-driven) rather than automated weaning systems (ie, computer-driven) (Grade 2C). We prefer manual protocols because they can be tailored to the patient, they are less costly, and because most of the available clinical trials used manual protocols. Automated systems are a reasonable alternative. (See 'Selecting manual or automated weaning' above.)

•For most patients, we suggest weaning via once-daily spontaneous breathing trials (SBTs), rather than gradual pressure support ventilation (PSV) or intermittent mandatory ventilation (IMV) weaning (Grade 2C). While gradual PSV and IMV weaning have been used in the past, the available evidence suggests that they are likely not superior to SBT. (See 'Daily spontaneous breathing trials (SBTs)' above and 'Alternative methods' above.)

•For most patients, we suggest that the SBT be performed with low-level PSV (eg, 5 to 8cm H₂O) rather than through a T-piece (Grade 2B). Automatic tube compensation (ATC) or continuous positive airway pressure (CPAP) are reasonable alternatives to low-level PSV. T-piece trials may be appropriate in select patients if there is concern that a PSV trial may provide a falsely reassuring assessment of readiness to extubate (eg, patients with acute cardiogenic pulmonary edema and patients with hypercapnia from obstructive lung disease). (See 'Choosing ventilatory support' above.)

•An initial SBT of 30 minutes duration is generally sufficient to determine whether mechanical ventilation can be discontinued. Trials of up to 120 minutes are appropriate for patients who fail their initial SBT and those with prolonged mechanical ventilation duration (eg, ≥10 days). (See 'Trial duration' above.)

●Assessment of weaning success or failure – Clinical impression determines whether a patient fails or tolerates weaning. (See 'Assessment of weaning success or failure' above.)

•Criteria for failure – Objective criteria used during weaning trials are listed in the table (table 2); the development of one or more of these indicates weaning failure. (See 'Clinical assessment' above.)

•Weaning success – Patients who tolerate the SBT should be evaluated for extubation. The approach to extubating patients in the intensive care unit (ICU) is discussed separately. (See 'Weaning success' above and "Extubation management in the adult intensive care unit".)

•Weaning failure – Patients who fail the SBT should be returned to previous ventilator settings. The reason for failure should be sought and corrected before resuming further weaning trials (table 3). Subsequently, the patient should be assessed for readiness to wean with daily SBTs. The approach to managing such patients is discussed separately. (See 'Weaning failure' above and "Management of the difficult-to-wean adult patient in the intensive care unit".)

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REFERENCES

Weaning from mechanical ventilation: Readiness testing

Author: Scott K Epstein, MD
Section Editor: Polly E Parsons, MD
Deputy Editor: Geraldine Finlay, MD

Contributor Disclosures

All topics are updated as new evidence becomes available and our peer review process is complete.

Literature review current through: Apr 2022. | This topic last updated: Feb 04, 2022.

INTRODUCTIONLiberation from mechanical ventilation is a three-step process that involves readiness testing, weaning, and extubation. Criteria for readiness testing are reviewed here. Weaning and extubation are discussed separately. (See "Initial weaning strategy in mechanically ventilated adults" and "Extubation management in the adult intensive care unit".)

DEFINITIONS

Readiness testing — Readiness testing uses objective clinical criteria (and occasionally physiological tests) to determine whether a patient is ready to begin weaning from mechanical ventilation. (See 'Clinical criteria' below and 'Weaning predictors' below.)

Weaning — Weaning is the process of decreasing the degree of ventilator support and allowing the patient to assume a greater proportion of their own ventilation (eg, spontaneous breathing trials or a gradual reduction in ventilator support). (See "Extubation management in the adult intensive care unit" and "Initial weaning strategy in mechanically ventilated adults".)

Extubation — Extubation is the removal of the endotracheal tube and is the final step in liberation from mechanical ventilation support. Extubation is performed when the patient is successful at weaning and both airway patency and airway protection measures are in place. (See "Extubation management in the adult intensive care unit".)

GOALSReadiness testing identifies patients who are ready to wean as well as those who are not ready to wean from mechanical ventilation. Identifying those who are ready to wean avoids unnecessary mechanical ventilation and thereby, also avoids the risk of death and complications related to mechanical ventilation (eg, pulmonary barotrauma, ventilator-associated lung injury) [1,2]. Similarly, identifying patients who are not ready to wean protects patients from the risks of premature weaning (eg, cardiovascular dysfunction, respiratory muscle fatigue, psychological distress). (See "Physiologic and pathophysiologic consequences of mechanical ventilation" and "Ventilator-induced lung injury" and "Diagnosis, management, and prevention of pulmonary barotrauma during invasive mechanical ventilation in adults".)

DAILY SCREENING LIBERATION ASSESSMENTWe and others agree that patients who are mechanically ventilated for more than 24 hours should undergo daily ventilator liberation protocol assessment [3,4].

Liberation protocols contain guidance regarding readiness for weaning as well as the performance of subsequent weaning trials and extubation. Support for daily protocolized liberation strategies comes from the observation that clinicians consistently underestimate the capacity of patients to breathe independently from the ventilator [5-15] and data from randomized trials which have demonstrated benefit from protocol use when compared with usual care [4,16-19]. Consequently, some intensive care units (ICUs) have incorporated liberation protocols into routine care for mechanically ventilated patients.

However, considerable global variation exists in the use of protocols to guide weaning [20,21]. Best illustrating this variation was a multicenter, international prospective observational study of 1868 patients who were mechanically ventilated for at least 24 hours and admitted to one of 142 intensive care units (ICUs) in six geographic regions (Canada, US, UK, Europe, India, Australia/New Zealand) [21]. Written directives to screen for readiness ranged from 5 to 83 percent and were present in more than half of participating ICUs in Canada (56 percent), India (70 percent), and the United States (83 percent). However, written directives for SBT conduct were present in less than half of ICUs outside of the US, where directives were used in 78 percent of US ICUs. Similarly, the frequency of screening (eg, never, once daily, twice daily) also varied widely; once daily screening occurred in more than half of ICUs in Canada (67 percent), India (74 percent), and the US (83 percent), while lower rates were seen in the other regions.

Liberation protocols may not be beneficial in all settings and should be tailored to the patient population in which they will be applied. For example, liberation protocols have not been shown to be superior to usual care in highly staffed, closed ICUs in an academic hospital [22]. As another example, a liberation protocol did not improve outcome in neurologic patients [23], but adding a neurologic assessment led to a reduction in the need for reintubation among this population [24].

Data that support the value of liberation protocols that prompt spontaneous breathing trials (SBTs) are discussed separately. (See "Initial weaning strategy in mechanically ventilated adults", section on 'Daily spontaneous breathing trials (SBTs)'.)

CLINICAL CRITERIAClinical criteria that are listed in the table (table 1) should be used to identify patients who are ready to begin weaning [25]. While these criteria are widely used, it should be recognized that up to 30 percent of patients who never satisfy such criteria may be successfully weaned [9].

To be considered ready for weaning, patients should have all of the following:

●Improvement in the underlying cause of respiratory failure,

●Adequate oxygenation

●An arterial pH >7.25

●Hemodynamic stability

●Ability to take spontaneous respirations.

Other criteria that are ideally in place but not critical for readiness assessment include a hemoglobin level ≥7 g/dL, core temperature ≤38.5ºC, and an awake or easily arousable mental status (eg, sedation may need to be titrated to a target goal such as Richmond agitation-sedation scale [RASS] -2 to +1). (See "Sedative-analgesic medications in critically ill adults: Selection, initiation, maintenance, and withdrawal".)

These criteria are derived from studies that predicted successful weaning with their use performed within the context of a liberation protocol:

●A randomized trial of 304 mechanically ventilated patients compared those who underwent readiness testing using objective clinical criteria alone with those who underwent readiness testing using objective clinical criteria plus a weaning predictor, the rapid shallow breathing index [26] (see 'Rapid shallow breathing index' below). The group that used objective clinical criteria alone took one day less to discontinue mechanical ventilation. There was no difference in length of stay or reintubation rate. This trial is discussed in greater detail separately. (See 'Clinical outcomes' below.)

●The Awakening and Breathing Controlled (ABC) trial screened 336 mechanically ventilated patients daily for adequate oxygenation (peripheral oxygen saturation [SpO₂] >88 percent while receiving a fraction of inspired oxygen [FiO₂] <50 percent and a positive end-expiratory pressure [PEEP] ≤8 cm H₂O), for hemodynamic stability and any spontaneous inspiratory effort during a five-minute period, as well as the absence of agitation, myocardial ischemia, and increased intracranial pressure [27]. Weaning predictors were not measured. Those who passed the screen underwent a spontaneous breathing trial (SBT). More than 50 percent of patients who underwent an SBT tolerated it, suggesting that these criteria are reasonable indicators of successful weaning.

The complication rate of using readiness criteria for subsequent SBTs appears to be low. In a study of more than 1000 patients who underwent an SBT following the use of clinical readiness weaning criteria, only one complication was identified (<0.1 percent) [17]. Another study of 19 patients who underwent an SBT following readiness criteria found that low frequency fatigue, which can hinder future weaning attempts, did not occur [28].

Required criteria — Discussed in this section are the required clinical criteria, that are necessary before a patient can be considered ready to wean (table 1).

The underlying indication for mechanical ventilation has improved — In most cases, the underlying condition that precipitated intubation and mechanical ventilation should be improving as evidenced by clinical, radiological, and/or laboratory parameters (eg, fluid overload, pneumonia, acute respiratory distress syndrome).

Adequate oxygenation — Thresholds that determine adequate oxygenation are empiric. We consider oxygenation adequate when either the ratio of arterial oxygen tension to fraction of inspired oxygen (PaO₂/FiO₂) is ≥150 mmHg or when the SpO₂ is ≥90 percent while receiving an FiO₂ ≤40 percent and a PEEP ≤5 cm H₂O. For patients who have chronic hypoxemia, a PaO₂/FiO₂ ratio ≥120 mmHg may be used instead.

A higher level of PEEP may be acceptable in some patients to avoid atelectasis (eg, 8 cm H₂O in patients with obesity or abdominal distension for another reason such as ascites, or patients with a narrow endotracheal tube [ETT; eg, < 7cm]). Similarly, a slightly higher FiO₂ (eg, 0.5) may be acceptable if significant underlying lung disease is present.

Arterial pH >7.25 — Severe acute acid-base disturbances, in particular, an acute metabolic, respiratory, or mixed acidosis, should be resolving or estimated to be close to baseline prior to weaning. In most cases, the pH is within normal limits. However, in patients with chronic metabolic or respiratory acid-base disturbances, we try to obtain or estimate baseline values and ventilate patients at a target value that is close to their baseline (eg, patients with chronic hypercapnia, renal tubular acidosis). Although arbitrary, the value of an arterial pH >7.25 is reasonable based upon the observation that for most spontaneously breathing patients, it may be tolerated without undue load on the respiratory system. Exceptions exist including patients with worsening acid-base disturbance, those who cannot generate sufficient minute ventilation to compensate for acute acidosis (eg, those with neuromuscular weakness).

Hemodynamic stability — We generally consider that patients are ready to wean if they are hemodynamically stable and without myocardial ischemia. The blood pressure thresholds below or above which it is unsafe for a patient to wean have not been established. However, it is reasonable to require that the mean arterial pressure be consistently >60 mmHg, and/or the systolic blood pressure be >90 mmHg and <180 mmHg, or estimated to be at the patients baseline. The use of vasopressors to maintain hemodynamic stability is acceptable, but only low and stable doses should be necessary (eg, dopamine <5 mcg/kg/minute, low-dose dobutamine in patients with heart failure).

Ability to initiate inspiration — For weaning trials to begin, patients should be able to initiate inspiratory effort. We assess this by determining that the patient is breathing above the set respiratory rate on the ventilator. For patients who are breathing at or below the set rate, we temporarily reduce the set rate to a lower value for a brief period and ensure that the patient is able to initiate spontaneous breaths above the newly set value (eg, set ventilator rate at six breaths per minute for one minute).

Additional or optional requirement — When assessing patients readiness to wean, we take into consideration several additional criteria that are also listed in the table (table 1) [3,4]. While it is ideal that these criteria are in place, they are less critical to the success of weaning than the required criteria listed above (see 'Required criteria' above). These include the following:

●Hemoglobin level ≥7 g/dL – Anemia reduces oxygen carrying capacity and can affect successful weaning. While in the past, any degree of anemia was considered a contraindication to weaning, studies performed since then suggest that hemoglobin levels of approximately 7 to 8 g/dL or greater are appropriate targets for safe weaning. For example, a secondary analysis of a randomized trial reported no difference in the rate of successful weaning when a restrictive blood transfusion strategy (ie, maintain hemoglobin level of 7 to 9 g/dL) was compared to a liberal strategy (ie, maintain a hemoglobin level of 10 to 12 g/dL; 78 versus 82 percent) [29]. Similarly, another single center retrospective study of 138 difficult to wean patients found a higher probability of weaning success in patients with a hemoglobin level of ≥8 g/dL compared with patients who had a hemoglobin <8 g/dL [30]. No difference in weaning success was found in patients who have hemoglobin levels of 8 to 10 g/dL compared with those who have hemoglobin levels >10 g/dL.

●Core temperature ≤38.5ºC – The rationale for this criterion is that the presence of fever makes successful weaning less likely because it increases the minute ventilation and, thus, increases work of breathing [31]. In addition, fever may also result in diminished respiratory muscle function (eg, patients with sepsis) [32]. However, a temperature threshold above which weaning is unsafe has not been identified. It should be noted that this applies to patients with actual fever at the time of assessment and does not apply to individuals who are afebrile for periods in between intermittent spiking of fever.

●A mental status that is either awake and alert or easily arousable – Although an awake or easily arousable patient is ideal for weaning and more importantly, extubation, it is not always feasible (eg, due to sedatives or delirium). It has been shown that an abnormal mental status (eg, Glasgow Coma Scale score between 8 and 15 (table 2) or Richmond agitation-sedation scale -2 to +1) does not appear to be associated with a higher rate of extubation failure [33,34]. Thus, as long as a patient can protect their airway, an abnormal mental status does not preclude weaning. Evaluation of the ability to protect the airway for extubation is described separately. (See "Extubation management in the adult intensive care unit", section on 'Assess airway protection'.)

FOLLOW-UP

Patients who are ready to wean — For patients who are deemed ready to wean, we perform a weaning trial, which predicts the patients’ potential for spontaneous breathing following extubation. Details regarding methods of weaning are provided separately. (See "Initial weaning strategy in mechanically ventilated adults".)

Readiness testing is imperfect, and some patients deemed ready to wean fail a subsequent spontaneous breathing trial (SBT). Failed weaning has not been shown to be harmful if it is well monitored and the patient is returned to full ventilatory support at the first sign of intolerance (ie, ventilatory fatigue should be avoided). This justifies repeated daily readiness assessments and SBTs in those deemed ready to wean, provided the reason for weaning failure is investigated and treated (eg, excess sedation, development of myocardial ischemia, neuromuscular weakness, electrolyte disturbances).

Patients not ready to wean — For patients who do not meet readiness criteria, we continue to treat the underlying disorder or complications of mechanical ventilation until readiness criteria can be eventually met. In many cases, if the patient improves, they can undergo a weaning trial when ready. If they do not improve, then we assess the patients for long term mechanical ventilation with a tracheostomy. Management of the difficult to wean patient is discussed separately. (See "Management of the difficult-to-wean adult patient in the intensive care unit".)

Patients with uncertainty — For patients in whom uncertainty exists as to whether the readiness criteria will predict a successful weaning trial, we sometimes use a weaning predictor to identify potential candidates suitable for weaning or to confirm lack of readiness to wean (eg, patients with borderline readiness criteria or suspected respiratory muscle weakness). Use of weaning predictors is most pertinent among patients in whom the risk associated with a failed spontaneous trial is significantly elevated (eg, patients with prolonged mechanical ventilation, patients with critical care neuromyopathy).

Among the predictors, the rapid shallow breathing index (RSBI) is our preferred weaning predictor because it is well studied, easy to measure, and no alternative predictor has been shown to be superior. (See 'Rapid shallow breathing index' below.)

●For patients who have an RSBI <105 breaths/minute/L (measured without ventilatory support), we initiate a weaning trial.

●For patients who have an RSBI ≥105 breaths/minute/L (measured without ventilatory support), we maintain full ventilatory support.

For patients in whom neuromuscular weakness is suspected, we also sometimes measure the maximal inspiratory pressure and/or diaphragmatic ultrasound at the bedside to confirm our suspicion. (See 'Predictors not routinely used' below.)

Weaning predictors — Some clinicians use physiological tests (weaning predictors) in addition to clinical criteria to predict whether a patient is likely to tolerate weaning, while others, including us, only use them when doubt exists over a patients’ readiness to wean. Among the predictors, the RSBI is the most widely used and extensively studied (table 3). All other tests generally have poor predictive capacity or require complex testing.

Rapid shallow breathing index — The RSBI is the ratio of respiratory frequency to tidal volume (f/VT).

Measurement — We measure the f and VT using a hand-held spirometer attached to the endotracheal tube while a patient is breathing room air for one minute without any ventilator assistance [35]. The spirometer measures the total volume inspired and expired in one minute (ie, minute ventilation) while the operator counts the actual respiratory rate. The VT can be calculated by dividing the minute ventilation by the f. The f and VT can then be used to calculate the RSBI.

However, if a spirometer is not available or the patient cannot breathe room air, the RSBI may be calculated using the ventilator [36-39]. We set the ventilator to a pressure support level of 0 cm H₂O and a positive end-expiratory pressure (PEEP) of 0 cm H₂O, without flow or pressure trigger for one minute [38,39]. The tidal volume can then be determined by the ventilator. However, the respiratory rate should be manually counted since the ventilator may underestimate the respiratory rate if the patient makes inspiratory efforts that are not sensed by the ventilator. Such unmeasured inspiratory efforts falsely lower the RSBI, particularly in patients who have chronic obstructive lung disease with dynamic hyperinflation [40].

Interpretation — An RSBI ≥105 breaths/minute/L (ie, a negative RSBI) indicates that a patient is likely to fail weaning while a positive test RSBI <105 breaths/minute/L is more likely to undergo successful weaning. However, many experts adopt an individual approach to interpreting the threshold value and allow for factors that may falsely alter it. For example, several factors have been shown to increase the RSBI, including a narrow endotracheal tube (eg, ≤7 cm), female gender, sepsis, fever, supine position, anxiety, suctioning, and chronic restrictive lung disease [41,42]. Thus, interpretation may need to be adjusted individually under these circumstances.

Evidence suggests that a negative RSBI (RSBI ≥105 breaths/minute/L) is better at identifying patients who will fail weaning than a positive RSBI (RSBI <105 breaths/minute/L) is at identifying patients who can be successfully weaned [35,43,44]. RSBI was originally described in a prospective cohort study that evaluated 64 mechanically ventilated patients [35]. An RSBI ≥105 breaths/minute/L was associated with weaning failure, while an RSBI <105 breaths/minute/L predicted weaning success with a sensitivity, specificity, positive predictive value, and negative predictive value of 97, 64, 78, and 95 percent, respectively [35]. The pretest probability of weaning success in the study population was approximately 60 percent. When these data were used to calculate likelihood ratios, the LR+ was 2.7 and the LR- was 0.05 (table 4). This indicates that there is only a small increase in the probability of weaning success among patients with a positive RSBI (<105 breaths/minute/L). In contrast, there was a large increase in the probability of weaning failure among patients with a negative RSBI (≥105 breaths/minute/L). These findings were supported by a systematic review of 20 RSBI studies [43] and a bayesian analysis of the same studies [44].

Clinical outcomes — Routine use of the RSBI has not been shown to decrease duration of weaning or mechanical ventilation. As examples:

●In one trial, 304 mechanically ventilated patients had their RSBI measured daily and all of the patients underwent daily screening [26]. Patients randomized to RSBI-dependent weaning underwent an SBT if they passed all components of the screening and had an RSBI <105 breaths/minute/L. In contrast, patients randomized to RSBI-independent weaning underwent an SBT if they passed all components of the screening, regardless of their RSBI. The group that underwent RSBI-dependent weaning took one day longer to discontinue mechanical ventilation. There was no difference in the total duration of mechanical ventilation, length of stay, or reintubation rate.

●In a meta-analysis that pooled data from 48 studies, sensitivity for RSBI in predicting successful extubation was 83 percent, while specificity was low (58 percent) [45]. Results were consistent among several subgroups. The corresponding likelihood ratios (LR+ of 2.0, LR- of 0.3) translate to only a small increase in the probability of weaning success with a positive RSBI and a moderate probability of weaning failure with a negative RSBI.

Predictors not routinely used — Several other weaning predictors have been described but have poor predictive capacity, are investigational, have poorly defined thresholds, or require complex maneuvers for calculation. These predictors are listed in the table (table 3).

●Measurements of oxygenation and gas exchange – Although adequate oxygenation is an essential clinical criterion to consider when deciding whether a patient is ready to wean (see 'Clinical criteria' above), it is a poor weaning predictor when used alone to predict weaning outcome. These include the following:

•The ratio of arterial oxygen tension to fraction of inspired oxygen (PaO₂/FiO₂)

•The ratio of arterial oxygen tension to alveolar oxygen tension (PaO₂/PAO₂)

•The alveolar-arterial (A-a) oxygen gradient

•Measures of dead space

●Measurements of load on the respiratory system and respiratory capacity (some require special equipment) ─ None of the following parameters have been shown to consistently predict successful weaning or failure to wean:

•Minute ventilation [43]

•Respiratory system compliance [35,46]

•Work of breathing [47-51]

•Oxygen cost of breathing [52-54]

•Occlusion pressure (P0.1) [55-57] and (P0.1/maximum inspiratory pressure ratio) [58,59]

•Maximal inspiratory pressure

•Gastric mucosal acidosis [60,61]

•Diaphragmatic ultrasound [62-66]

•Esophageal pressure [43]

•Diaphragmatic pressure during a spontaneous tidal breath [43]

•Tension-time index [43]

●Multicomponent integrative indices – RSBI is the best example of an integrated index. While several of the more complicated integrated indices looked promising, none have been confirmed as having the high level of accuracy that was initially reported. These include:

•Inspiratory effort quotient (IEQ) [67]

•The CROP index (Compliance, Rate, Oxygenation, Pressure) [35]

•The CORE index (Compliance, Oxygenation, Respiration, Effort) [68]

•Weaning Index (WI) [69]

•Integrative weaning index (IWI) [46]

SOCIETY GUIDELINE LINKSLinks to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Weaning from mechanical ventilation".)

SUMMARY AND RECOMMENDATIONS

●Discontinuing mechanical ventilation is a three-step process that consists of readiness testing, weaning, and extubation. During readiness testing, objective clinical criteria are used to determine whether a patient is ready to begin weaning. Weaning is the process of decreasing the degree of ventilator support and allowing the patient to assume a greater proportion of their own ventilation. Extubation is the removal of the endotracheal tube (ETT). (See 'Introduction' above and 'Definitions' above.)

●The purpose of readiness testing is to identify patients who are ready to wean, since clinicians tend to underestimate the capacity of patients to breathe independently. Early identification of patients who may be extubated avoids risk of death and complications related to mechanical ventilation (eg, pulmonary barotrauma, ventilator-associated lung injury). Readiness testing is also intended to identify patients who are not ready for weaning, thereby protecting them against the potential risks of premature weaning (eg, cardiovascular dysfunction, respiratory muscle fatigue, psychological distress). (See 'Goals' above.)

●For patients who are mechanically ventilated for more than 24 hours, we perform daily ventilator liberation protocol assessment rather than non-protocolized assessment. However, wide variation exists in practice. (See 'Daily screening liberation assessment' above.)

●Reasonable objective clinical criteria used to predict readiness for weaning are listed in the table (table 1). (See 'Clinical criteria' above.)

●Based on the assessment, we suggest the following approach (see 'Follow-up' above):

•For patients who are deemed ready to wean, we suggest a weaning trial (Grade 2C). (See 'Patients who are ready to wean' above.)

•A weaning trial is not typically performed in patients who do not meet readiness criteria. Daily readiness assessment should be continued. (See 'Patients not ready to wean' above.)

•For patients in whom uncertainty exists, we sometimes use a weaning predictor to identify potential candidates suitable for weaning or to confirm lack of readiness to wean. Among the predictors (table 3), the rapid shallow breathing index (RSBI) is our preferred weaning indicator because it is well studied, easy to measure, and no alternative weaning predictor has been shown to be superior. However, there is no evidence that RSBI-dependent weaning improves clinical outcomes, such as duration of weaning, duration of mechanical ventilation, length of stay, or reintubation rate. (See 'Patients with uncertainty' above and 'Weaning predictors' above.)

-For patients who have an RSBI 105 breaths/minute/L (measured without ventilatory support), we initiate a weaning trial.

-For patients who have an RSBI ≥105 breaths/minute/L, we maintain full ventilatory support.

•Several other weaning predictors have been described but have poor predictive capacity, are investigational, have poorly defined thresholds, or require complex maneuvers for calculation (table 3).

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REFERENCES

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