Logout
 CME Information
 Editorial Board
 Lessons by Volume
   Volume 22
   Volume 21
   Volume 20
   Volume 19
   Volume 18
   Volume 17
   Volume 16
   Volume 15
 
 

Lesson 10, Volume 15—Weaning From Mechanical Ventilation: Acute and Chronic Management

By E. Wesley Ely, MD, MPH, FCCP

Effective December 31, 2004, PCCU Volume 15 is available for review purposes only. CME credit for this volume is no longer being offered.

Objectives

  1. Outline the magnitude of the problem of liberation from mechanical ventilation.
  2. Review evidence in support of protocol-driven weaning from the ventilator.
  3. Discuss salient issues related to spontaneous breathing trials.
  4. Focus on clinical decisions regarding extubation.
  5. Overview approaches to management of chronic ventilator-dependent patients.

Key words

clinical protocols; critical; mechanical ventilation; respiratory therapy; ventilator weaning

Abbreviations

AHCPR = Agency for Healthcare Policy and Research; FIO2 = fraction of inspired oxygen; HCP = health-care professional; MV = mechanical ventilation; PMV = prolonged mechanical ventilation; RCP = respiratory-care practitioner

In just the past 5 years, more than 500 articles have been written on weaning from artificial respiration, underscoring the interest in, importance of, and uncertainties about this clinical issue. Many advances have been made regarding the optimal methods of reducing and removing patients from mechanical ventilation (MV). These efforts are important because the duration of MV is associated with considerable morbidity, including ventilator-associated pneumonia, mortality, and costs.1,2-4 On the other hand, premature removal from MV can also contribute to failed extubation, nosocomial pneumonia, and increased mortality.5-7 Until recent years, physicians have most often approached the discontinuation of MV through a gradual reduction in ventilatory support, reflected in universally applied but varying forms of "weaning." This gradual approach may unnecessarily delay extubation of patients who have recovered from respiratory failure. With increasing attention placed on the considerable resources consumed during the care of patients with respiratory failure, a change in the culture of weaning is well-supported by the literature. Evidence supports the concept of liberation from MV8-10: that the timely recognition of patients having recovered from respiratory failure is more important than manipulation of MV in an attempt to accelerate recovery. Furthermore, utilizing the talents of nonphysician health-care professionals (HCPs) can improve the outcomes of patients.

The McMaster Evidence-Based Practice Center has conducted a comprehensive review of the literature regarding weaning to address key questions posed by the Agency for Healthcare Policy and Research (AHCPR).1 To create this 380-page document, in which they considered 5,653 articles from 1971 to 1999, the authors chose 154 manuscripts for final review and evaluation. Among the many aspects of weaning that were reviewed by the McMaster AHCPR investigators, the strongest conclusions were drawn in regard to the development and implementation of ventilator weaning protocols and the use of nonphysician HCPs (eg, respiratory-care practitioners [RCPs] and nurses) in the ICU to enhance patients’ liberation from MV. These protocols may be organized and led by physician opinion leaders, yet driven on a daily basis by nonphysician HCPs.

Evidence in Support of Protocol-Driven Weaning
for Mechanical Ventilation

There is abundant evidence that allied HCPs can implement protocols that enhance clinical outcomes for critically ill patients in diverse areas, such as performance of appropriate blood gas analysis or chest physiotherapy.11-16 Indeed, respiratory care protocols (also known as therapist-driven or patient-driven protocols), have been investigated in the general management of patients quite extensively during the past few years.17-20 From these investigations, we have learned that use of protocols enhances the allocation of respiratory care services, with improved clinical outcomes and cost savings. Effective implementation of protocols requires adequate staffing, and it has been shown that if staffing is reduced below certain thresholds, clinical outcomes may be jeopardized.21,22 Indeed, in the specific context of liberation from MV, reductions in nurse-to-patient ratios have been associated with prolonged duration of mechanical ventilation.23

Conclusion: Based upon the literature referenced above, we conclude that nonphysician HCPs can provide protocol-based care that enhances outcomes for patients with respiratory care needs (not limited to liberation from MV).

The McMaster evidence-based AHCPR report on weaning1 concluded that the best method for liberating patients from MV was to employ a protocol implemented by nurses and RCPs, beginning readiness testing soon after intubation and the initiation of MV. A major transition in thought regarding weaning began in 1994 and 1995, when it was demonstrated for the first time in randomized, controlled trials that one modality of weaning might be superior to another if executed in a specified fashion.9,24 However, there remained no data from randomized, controlled trials to firmly establish whether a weaning protocol was superior to the standard of care, which was an individual physician’s best management.25 Simultaneously, two randomized, controlled trials encompassing experience in 657 patients demonstrated that outcomes for mechanically ventilated patients who were managed using protocols and systematic trials of spontaneous breathing were improved over those of control patients managed with standard care.10,26

Specifically, in 1996, Ely et al10 reported a two-step protocol driven by nurses and RCPs incorporating a daily screen followed by a spontaneous breathing trial. Although the 151 patients managed in the medical ICU and critical care unit with the protocol had a higher severity of illness than the 149 control patients, they had 2 days less "weaning," 50% fewer complications related to the ventilator, and mean ICU costs of care that were lower by more than $5,000 per patient.10 In a slightly larger trial with a more diverse patient population published in 1997, Kollef et al26 used three different RCP- and nurse-driven weaning protocols and showed that the mean duration of MV could be reduced by 30 h. Numerous other investigators have shown the benefits of a protocolized approach to weaning in multiple settings.27-29 The implementation of nurse- or RCP-driven weaning protocols, regardless of the specific MV weaning mode employed, significantly expedites safe liberation.1,20

The reproducibility of benefit achieved by these approaches in different ICUs and institutions suggests that it is the use of a protocol and the culture change in which protocols develop that effects benefit, rather than any specific modality of weaning. Indeed, when other key features in the management of ventilated patients are protocolized, such as sedation and analgesia, further reductions in the time on MV can be realized. In the randomized, controlled trial of a nursing-implemented sedation protocol (n = 321) for mechanically ventilated patients performed by Brook et al,30 the use of the protocol was associated with a 50% reduction in the duration of MV, and 2- and 3-day reductions in the median ICU and hospital lengths of stay (p < 0.01 for all). Tracheostomy rates were also reduced in this study, and no increased rates of adverse outcomes—such as self-extubations, reintubations, or undue anxiety—were noted. Subsequent reports of the interruption of sedative drips in order to allow daily awakening trials in mechanically ventilated patients have confirmed reductions in the length of stay on the ventilator.31

Published data do not support endorsing any one protocol (although some guidelines are offered below), and choice of a specific protocol is best left to the individual institution. Importantly, each institution must endorse the fiscal commitment and the staffing modifications necessary for developing and implementing a multidisciplinary weaning protocol team of dedicated HCPs.32 While institutions must customize protocols to local practices, several important general concepts may ease the process of implementation and enhance success.

It is imperative that protocols not be used to replace clinical judgment, but rather to complement it. Protocols are meant as guides in patient management, and can serve as the general default management decision unless any of the HCPs (physicians, nurses, or RCPs) can justify a departure from the protocol. Likewise, protocols should not be viewed as static constructs, but rather as dynamic tools in evolution that can be molded to accommodate new data and/or HCPs’ preferences. More studies regarding the impact of protocol-based weaning are needed to better delineate approaches to specific patient populations (eg, neurosurgical or trauma patients), in specific organizational structures (eg, open vs closed units, teaching vs community hospitals), and using computer-assisted decision-making.

Conclusion: Randomized, controlled trials demonstrate that protocols for liberating patients from mechanical ventilation driven by nonphysician HCPs result in improved clinical outcomes.

Spontaneous Breathing Trials

The aforementioned protocols each used a two-step method of daily screening at the bedside followed by spontaneous breathing trials in those who passed screening criteria. The daily screen may vary depending on the patient population, but generally includes an assessment of adequacy of oxygenation (eg, ratio of PaO2 to the fraction of inspired oxygen [FIO2] > 200 on positive end-expiratory pressure £ 5 cm H2O) and ventilation (frequency/tidal volume ratio £ 105 breaths/min/L, which can be measured after 1 min of spontaneous breathing with ventilator rate set to 0 and pressure support set to 0). Given the low negative predictive value of most weaning parameters,4,33,34 we feel that clinicians should have a low threshold for performing a daily assessment of the patient’s ability to breathe spontaneously. 9,10,24,26 Patients chosen for a spontaneous breathing trial should be stable hemodynamically and improving with regard to the initial cause of respiratory failure. Spontaneous breathing trials can be performed safely in the "out of study" setting by nonphysician HCPs using any of several validated methods. The trial itself can be performed using a T-piece, continuous positive airway pressure without pressure support, with pressure support up to 7 cm H2O, and for durations of 30 min to 2 h.7,10,26,32,35 The monitored assessment of spontaneous breathing should be conducted at least once daily, and should be integrated with other major events in the patient’s daily care including the cessation or temporary reduction in delivery of sedation and analgesia medications.30 In the context of emerging data about the benefits of noninvasive positive pressure ventilation36,37 and the substantial roles of RCPs in providing this treatment, there is enthusiasm for developing and studying protocols in which RCPs execute weaning protocols using this modality.

Conclusion: An empirical approach to a trial of weaning (spontaneous breathing trial) is safe and indicated.

Clinical Decisions Regarding Extubation

When a patient does not demonstrate readiness for liberation from the mechanical ventilator, but is improving with lessening support requirements, the clinician is often left to wonder what to do with MV. Two of the aforementioned randomized, controlled trials9,24 addressed this dilemma. Both Esteban et al9 and Brochard et al24 employed a screening process whereby patients were enrolled into the trials only if they failed to demonstrate readiness via a spontaneous breathing trial. In these studies, either once-daily spontaneous breathing trials or pressure support ventilation were both superior to intermittent mandatory ventilation alone. Reported differences in the superiority of spontaneous breathing trials vs pressure support ventilation have been attributed to variations in the management protocols. The value of differing modes depends upon thresholds for initiating, progressing through, and terminating weans. Unfortunately, these thresholds involve more than objective data and appear related to physician judgment.1

Conclusion: When a patient appears to be improving, but cannot either oxygenate or ventilate adequately when breathing spontaneously, we recommend the following:

  1. All remediable factors to enhance the prospects of successful liberation from MV should be addressed (eg, electrolyte derangements, bronchospasm, malnutrition, excess secretions, etc.).
  2. The patient should be placed on a comfortable, safe, and well-monitored mode of MV such as pressure support ventilation, synchronized intermittent mandatory ventilation with pressure support ventilation, or extubated with support using noninvasive positive pressure ventilation.
  3. Few data support multiple manipulations of ventilator settings each day in an effort to wean or "train" the patient. In fact, these efforts may be viewed as a waste of precious resources (both person-power and time). Strategies that incorporate periodic "resting" of the patient for varying intervals on control-mode MV have been advocated by some, but have not been associated with superior outcomes. For clinicians who prefer to continue step-wise reductions in MV, it appears that multiple daily spontaneous breathing trials or pressure support ventilation are superior to intermittent mandatory ventilation.9,24 Whichever mode is used, at least a once-daily spontaneous breathing trial should be incorporated as mentioned above.
  4. Patients’ abilities to breathe spontaneously should be assessed at the risk of failure, but in the face of repeated failures, clinicians must then consider longer-term options, including both tracheotomy and a chronic or step-down ventilator facility.36

The above-mentioned investigations outlined either a rigid extubation protocol, or one combined with the clinician’s gestalt and preference for timing of extubation.7,9,10,24,26 Despite the care and rigor with which a team of HCPs evaluates their patients’ abilities to be liberated from MV, some patients will require reintubation and will go on to develop complications. However difficult to foresee in some patients,6,38 extubation failure should be avoided whenever possible, because the need for reintubation carries eight-fold higher odds for nosocomial pneumonia39 and six- to 12-fold increased mortality.5,7,35,40 It has become clear that the most important determinants of the morbidity associated with reintubation relate to its cause in each patient (ie, extubation failure due to airway compromise vs true weaning or "pump" failure) and the time to reintubation.6 Thus, recognition that decisions regarding MV discontinuation and extubation are distinct from one another has fundamental importance.

Reported reintubation rates range from 4 to 20% for different ICU populations,5-7,9,10,24,32,41 and may be as high as 33% in patients with mental status changes and neurologic impairment.38 The optimal rate of reintubation is not known, but likely rests between 5 and 15%. Two investigations have shown an associated reduction in reintubation rates by incorporating a protocol driven by nonphysician HCPs.10,42

Unplanned extubation can occur in patients who self-extubate because they have recovered but are not yet liberated. On the other hand, unplanned extubation can result from either self-extubation or accidental extubation in patients inadequately sedated and/or restrained. It has been known for some time that when self-extubation occurs, patients frequently (in about 50% of instances) do not require reintubation,40,43-46 a fact that should further motivate physicians to adopt proactive protocols directed toward earlier extubation.

Conclusion: The decision to extubate the patient must be guided by objective information but be combined with clinical acumen in order to reduce unnecessary reintubations and self-extubations.

Management of Chronic Ventilator-Dependent Patients

Approximately 20% of patients in the critical-care setting will need prolonged mechanical ventilation (PMV), defined as > 21 days of MV; PMV is reimbursed partially by the Health Care Financing Administration.47,48 Protocols in the acute ICU setting have been shown in randomized, controlled trials to reduced the incidence of PMV.10 As the aging of our population becomes more and more prominent, there are data to suggest that the proportion of patients requiring PMV will become greater.49-51 There are more than 30 studies, most of them observational and none of them randomized trials, on post-ICU weaning from the ventilator. Most studies support the conclusion that ICU patients who require PMV can be weaned safely and effectively when transferred to units dedicated to that activity. Whether free-standing or within the hospital of ICU origin, these units are characterized by less intensive staffing and less costly monitoring equipment.52,53

Conclusion: Intensivists should familiarize themselves with units in their hospital or facilities in their community that specialize in weaning patients from PMV. In the absence of a terminal and irreversible prognosis, patients who have failed to wean in the ICU should be transferred to a facility with demonstrated success and safety in weaning from PMV.

References

  1. Cook DJ, Meade MO, Guyatt GH, et al, for the McMaster Evidence-Based Practice Center. Weaning from mechanical ventilation. Agency for Healthcare Research and Quality (Contract No. 290-97-0017, Task order number 2), 2000
  2. Cook DJ, Walter SD, Cook RJ, et al. Incidence of and risk factors for ventilator-associated pneumonia in critically ill patients. Ann Intern Med 1998; 129:433-439
  3. Ely EW, Baker AM, Evans GW, et al. The cost of respiratory care in mechanically ventilated patients with chronic obstructive pulmonary disease. Crit Care Med 2000; 28:408-413
  4. Ely EW, Baker AM, Evans GW, et al. The prognostic significance of passing a daily screen of weaning parameters. Intensive Care Med 1999; 25:581-587
  5. Epstein SK, Ciubotaru RL, Wong JB. Effect of failed extubation on the outcome of mechanical ventilation. Chest 1997; 112:186-192
  6. Epstein SK, Ciubotaru RL. Independent effects of etiology of failure and time to reintubation on outcome for patients failing extubation. Am J Respir Crit Care Med 1998; 158:489-493
  7. Esteban A, Alia I, Gordo F, et al. Extubation outcome after spontaneous breathing trials with T-tube or pressure support ventilation. Am J Respir Crit Care Med 1997; 156:459-465
  8. Hall JB, Wood LD. Liberation of the patient from mechanical ventilation. JAMA 1987; 257:1621-1628
  9. Esteban A, Frutos F, Tobin MJ, et al. A comparison of four methods of weaning patients from mechanical ventilation. N Engl J Med 1995; 332:345-350
  10. Ely EW, Baker AM, Dunagan DP, et al. Effect on the duration of mechanical ventilation of identifying patients capable of breathing spontaneously. N Engl J Med 1996; 335:1864-1869
  11. Brock WA, Nolan K, Nolan T. Pragmatic science: accelerating the improvement of critical care. New Horizons 1998; 6(1):61-68
  12. Clemmer TP, Spuhler VJ. Developing and gaining acceptance for patient care protocols. New Horizons 1998; 6(1):12-19
  13. Kollef MH, Horst HM, Prang L, et al. Reducing the duration of mechanical ventilation: three examples of change in the intensive care unit. New Horizons 1998; 6(1):52-60
  14. Alexander E, Weingarten S, Mohsenifar Z. Clinical strategies to reduce utilization of chest physiotherapy without compromising patient care. Chest 1996; 110:430-432
  15. Browning JA, Kaiser DL, Durbin CG. The effect of guidelines on the appropriate use of ABG analysis in the intensive care unit. Respir Care 1989; 34:269-276
  16. Hart SK, Dubbs W, Gil A, et al. The effects of therapist evaluation of orders and interaction with physicians on the appropriateness of respiratory care. Respir Care 1989; 34:185-190
  17. Komara J, Stoller JK. The impact of a postoperative oxygen therapy protocol on use of pulse oximetry and oxygen therapy. Respir Care 1995; 40:1125-1129
  18. Stoller JK, Mascha EJ, Kester L, et al. Randomized controlled trial of physician-directed versus respiratory therapy consult service-directed respiratory care to adult non-ICU inpatients. Am J Respir Crit Care Med 1998; 158:1068-1075
  19. Stoller JK, Skibinski CI, Giles DK, et al. Physician-ordered use of a respiratory therapy consult service: results of a prospective observational study. Chest 1996; 110:422-429
  20. Stoller JK. The rationale for respiratory care protocols: an update. Respir Care 1998; 43:719-723
  21. Fridkin SK, Pear SM, Williamson TH, et al. The role of understaffing in central venous catheter-associated bloodstream infections. Infect Control Hosp Epidemiol 1996; 17:150-158
  22. Archibald LK, Manning ML, Bell LM, et al. Patient density, nurse-to-patient ratio and nosocomial infection risk in a pediatric cardiac intensive care unit. Pediatr Infect Dis 1997; 16:1045-1048
  23. Thorens JB, Kaelin RM, Jolliet P, et al. Influence of the quality of nursing on the duration of weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease. Crit Care Med 1995; 23:1807-1815
  24. Brochard L, Rauss A, Benito S, et al. Comparison of three methods of gradual withdrawal from ventilatory support during weaning from mechanical ventilation. Am J Respir Crit Care Med 1994; 150:896-903
  25. Stoller JK. Why therapist-driven protocols? Respir Care 1994; 39:706-708
  26. Kollef MH, Shapiro SD, Silver P, et al. A randomized, controlled trial of protocol-directed versus physician-directed weaning from mechanical ventilation. Crit Care Med 1997; 25:567-574
  27. Saura P, Blanch L, Mestre J, et al. Clinical consequences of the implementation of a weaning protocol. Intensive Care Med 1996; 22:1052-1056
  28. Wood G, MacLeod B, Moffatt S. Weaning from mechanical ventilation: physician-directed vs a respiratory-therapist-directed protocol. Respir Care 1995; 40:219-224
  29. Horst HM, Mouro D, Hall-Jenssens RA, et al. Decrease in ventilation time with a standardized weaning process. Arch Surg 1998; 133:483-488
  30. Brook AD, Ahrens TS, Schaiff R, et al. Effect of a nursing implemented sedation protocol on the duration of mechanical ventilation. Crit Care Med 1999; 27:2609-2615
  31. Kress JP, Pohlman AS, O’Connor MF, et al. Daily interruption of sedative infusions in critically ill patients undergoing mechanical ventilation. N Engl J Med 2000; 342:1471-1477
  32. Ely EW, Bennett PA, Bowton DL, et al. Large scale implementation of a respiratory therapist-driven protocol for ventilator weaning. Am J Respir Crit Care Med 1999; 159:439-446
  33. Chatila W, Jacob B, Guaglionone D, et al. The unassisted respiratory rate-tidal volume ratio accurately predicts weaning outcome. Am J Med 1996; 101:61-67
  34. Krieger BP, Ershowsky P, Becker DA, et al. Evaluation of conventional criteria for predicting successful weaning from mechanical ventilatory support in elderly patients. Crit Care Med 1989; 17:858-861
  35. Esteban A, Alia I, Tobin M, et al. Effect of spontaneous breathing trial duration on outcome of attempts to discontinue mechanical ventilation. Am J Respir Crit Care Med 1999; 159:512-518
  36. Nava S, Ambrosino N, Clini E, et al. Noninvasive mechanical ventilation in the weaning of patients with respiratory failure due to chronic obstructive pulmonary disease: a randomized controlled trial. Ann Intern Med 1998; 128:721-728
  37. Girault C, Daudenthun I, Chevron V, et al. Noninvasive ventilation as a systematic extubation and weaning technique in acute-on-chronic respiratory failure. Am J Respir Crit Care Med 1999; 160:86-92
  38. Vallverdu I, Calaf N, Subirana M, et al. Clinical characteristics, respiratory functional parameters, and outcome of a two-hour T-piece trial of patients weaning from mechanical ventilation. Am J Respir Crit Care Med 1999; 158:1855-1862
  39. Torres A, Gatell JM, Aznar E. Re-intubation increases the risk of nosocomial pneumonia in patients needing mechanical ventilation. Am J Respir Crit Care Med 1995; 152:137-141
  40. Chevron V, Menard J, Richard J, et al. Unplanned extubation: risk factors of development and predictive criteria for reintubation. Crit Care Med 1998; 26:1049-1053
  41. Burrowes P, Wallace C, Davies JM, et al. Pulmonary edema as a radiologic manifestation of venous air embolism secondary to dental implant surgery. Chest 1992; 101:561-562
  42. Wood KE, Flaten AL, Reedy JS, et al. Use of a daily wean screen and weaning protocol for mechanically ventilated patients in a multidisciplinary tertiary critical care unit [abstract]. Crit Care Med 1999; 27:A94
  43. Listello D, Sessler C. Unplanned extubation: clinical predictors for reintubation. Chest 1994; 105:1496-1503
  44. Tindol GA, Jr., DiBenedetto RJ, Kosciuk L. Unplanned extubations. Chest 1994; 105:1804-1807
  45. Boulain T. Unplanned extubations in the adult intensive care unit: a prospective multicenter study; Association des Reanimateurs du Centre-Ouest. Am J Respir Crit Care Med 1998; 157:1131-1137
  46. Betbese AJ, Perez M, Rialp G, et al. A prospective study of unplanned endotracheal extubation in intensive care unit patients. Crit Care Med 1998; 26:1180-1186
  47. Scheinhorn DJ, Chao DC, Stearn-Hassenpflug M, et al. Post-ICU mechanical ventilation: treatment of 1,123 patients at a regional weaning center. Chest 1997; 111:1654-1659
  48. Scheinhorn DJ, Hassenpflug M. Provision of long-term mechanical ventilation. Crit Care Clin 2000; 14:819-832
  49. Seneff MG, Zimmerman JE, Knaus WA, et al. Predicting the duration of mechanical ventilation: the importance of disease and patient characteristics. Chest 1996; 110:469-479
  50. Seneff MG, Wagner D, Thompson D, et al. The impact of long-term acute-care facilities on the outcome and cost of care for patients undergoing prolonged mechanical ventilation. Crit Care Med 2000; 28:342-350
  51. Kurek CJ, Cohen IL, Lambrinos J, et al. Clinical and economic outcome of patients undergoing tracheostomy for prolonged mechanical ventilation in New York state during 1993: analysis of 6,353 cases under diagnosis-related group 483. Crit Care Med 1997; 25:983-988
  52. Gracey DR, Hardy DC, Naessens JM, et al. The Mayo ventilator-dependent rehabilitation unit: a 5-year experience. Mayo Clin Proc 1997; 72:13-19
  53. Dasgupta A, Rice R, Mascha EJ, et al. Four year experience with a unit for long-term ventilation (respiratory special care unit) at the Cleveland Clinic Foundation. Chest 1999; 116:447-455

Copyright ©2001 American College of Chest Physicians
 
 

3300 Dundee Road • Northbrook, Illinois 60062-2348 • (847) 498-1400 • (800) 343-2227
Copyright ©1999-2008 American College of Chest Physicians. All Rights Reserved.
ACCP Privacy Policy | ACCP Web Site Terms of Use