January 2002 / Volume 47 / Number 1 / Page 29
Bringing Scientific Evidence to the Ventilator Weaning and Discontinuation Process: Evidence-Based Practice Guidelines
Mechanical ventilatory support is a critical life sustaining modality for patients in respiratory failure. However, as the need for this support resolves, it is imperative that clinical attention be turned to the discontinuation process. Unnecessary prolongation of support is clearly associated with excess morbidity and costs. Clinical aggressiveness in the discontinuation process, however, must be tempered by the realization that premature removal of support can also induce patient harm.
Many questions face clinicians in dealing with the issue of discontinuing mechanical ventilatory support. Among these are: What are the reasons the patient required initiation/prolongation of mechanical ventilatory support, and is the patient stabilizing/reversing? What clinical signs/tests indicate that ventilator discontinuation is possible or likely? What is the best way to manage a patient who is not ready for discontinuation but who is improving? What is the role of tracheotomy? What is the role of specialized units or centers for the ventilator withdrawal process?
To help answer these questions using evidence-based approaches, 2 projects were initiated in 1999 that culminated in the development of the evidence-based practice guidelines published in this issue of RESPIRATORY CARE.
See the Special Article on Page 69
The first project was the McMaster University Evidence-Based Review of Weaning from Mechanical Ventilation.1 This effort was sponsored by the United States Agency for Health Care Policy and Research (AHCPR) and initially searched over 5,000 citations from several databases to come up with 154 studies deemed suitable for an evidence-based report. The final report for the AHCPR contained 15 comprehensive data tables and 15 appendices describing the details of the analyses. The second project was the establishment of a task force by the American Association for Respiratory Care (AARC), the American College of Chest Physicians (ACCP), and the Society for Critical Care Medicine (SCCM) to create a set of evidence-based clinical practice guidelines for ventilator weaning and discontinuation. This task force relied heavily on the McMaster AHCPR document for evidence-based material but also sought additional expertise for issues not specifically addressed in this report. The task force used a consensus process to formulate recommendations based on evidence when possible and used expert opinion when such evidence was lacking.
Although many useful recommendations are contained in these guidelines, 4 particular issues are worth additional emphasis. First, the task force reviewed a substantial body of data that indicated how poorly clinicians do at assessing ventilator discontinuation potential, especially in the patient deemed “ventilator dependent” for more than several days. This finding underscores the need for more focused assessment strategies for such patients. Second, the available data are quite clear in showing that the best indicator of ventilator discontinuation potential is the clinical assessment (eg, respiratory pattern, cardiovascular response, comfort/anxiety, oxygenation) of patients during 30–120 minute spontaneous breathing trials (SBTs). More complex "weaning parameters" focused on physiologic measurements—such as muscle strength, respiratory system mechanics, metabolic parameters, and work of breathing—add little to the assessment of individual patients for discontinuation potential. Third, for patients failing a SBT, there are virtually no data showing that progressive ventilator reduction strategies between every-24-hour SBTs offer any benefit in shortening the duration of ventilatory support. Put another way, more cost-effective use of health care professionals would seem better attained by searching for reversible causes of respiratory failure rather than ritualistic attempts at gradual reductions in ventilator settings. As long as SBTs are performed every 24 hours, stable, comfortable, assisted forms of ventilatory support aimed at providing a non-fatiguing breathing load seem all that is necessary. Finally, the evidence is very clear that nonphysician health care professionals (especially respiratory therapists) can effectively achieve all of these goals when operating under well designed ventilator management protocols.
Now that the 1999–2001 projects are complete, it is hoped that this comprehensive work will provide clinicians with solid evidence-based recommendations for clinical practice. In addition, it is also hoped that this report will show investigators where the important “holes” in our knowledge are, so that properly designed studies can be performed in the future.
Neil R MacIntyre MD FAARC
ACCP/AARC/SCCM Task Force on Ventilator Weaning and Discontinuation
Respiratory Care Services
Duke University Medical Center
Durham, North Carolina
- Criteria for Weaning from Mechanical Ventilation. Summary, Evidence Report/Technology Assessment: Number 23. AHRQ Publication No. 00-E028, June 2000. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/clinic/mechsumm.htm. Accessed December 5, 2001.