Version May 2024
INTRODUCTION — 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 [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".)
PREDICTORS — Prediction 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".)
PHYSIOLOGY — The 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 "Clinical and physiologic complications of mechanical ventilation: Overview", section on 'Respiratory muscle weakness'.)
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 PREFERENCES — For 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".)
TRACHEOSTOMY — Most 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".)
WEANING — Prolonged 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 intubated critically ill adult patients: Initial evaluation and prescription".)
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.
COMPLICATIONS — Patients receiving PMV suffer similar complications as their counterparts receiving short-term mechanical ventilation. (See "Clinical and physiologic complications of mechanical ventilation: Overview".)
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.
OUTCOMES — Family 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].
●In another retrospective study of 308 adults undergoing prolonged mechanical ventilation, in-LTAC mortality was higher for older age groups (31 percent for 40 to 59 years, 41 percent for 60 to 79 years, and 55 percent for age ≥80 years) [72]. In-LTAC mortality rate was highest for those with severe cognitive impairment (58 percent) and vegetative or minimally conscious states (51 percent).
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 [73].
Several studies report consistent rates of successful weaning, ranging from 47 to 60 percent [64,65,74-76]. 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 [74]. 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 [75]. In a study of patients with COPD undergoing weaning, duration of mechanical ventilation predicted the likelihood of weaning failure [76].
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 [77]. 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 [78]. 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 [79]. 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 [80]. 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 [81]. 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 [82]. 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 [83-87].
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 [88]. 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 [89].
Long-term cognitive impairment has been associated with the presence, severity, and duration of associated delirium in survivors of critical illness [90]. 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) in adults: Clinical features and diagnostic evaluation", 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 [91]. 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 [92]. 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 ICU — Patients 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.)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Melissa Miller, MD, who contributed to earlier versions of this topic review.
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