January 2002 / Volume 47 / Number 1 / Page 69
A Collective Task Force Facilitated by the American College of Chest Physicians, the American Association for Respiratory Care, and the American College of Critical Care Medicine
Pathophysiology of Ventilator Dependence
Criteria to Assess Ventilator Dependence
Managing the Patient Who Has Failed a Spontaneous Breathing Test
Role of Tracheotomy in Ventilator-Dependent Patients
The Role of Long-Term Facilities
The discontinuation or withdrawal process from mechanical ventilation is an important clinical issue. Patients are generally intubated and placed on mechanical ventilators when their own ventilatory and/or gas exchange capabilities are outstripped by the demands placed on them from a variety of diseases. Mechanical ventilation also is required when the respiratory drive is incapable of initiating ventilatory activity, either because of disease processes or drugs. As the conditions that warranted placing the patient on the ventilator stabilize and begin to resolve, attention should be placed on removing the ventilator as quickly as possible. Although this process often is termed “ventilator weaning” (implying a gradual process), we prefer the more encompassing term “discontinuation.”
See the Related Editorial on Page 29
Unnecessary delays in this discontinuation process increase the complication rate from mechanical ventilation (eg, pneumonia, airway trauma) as well as the cost. Aggressiveness in removing the ventilator, however, must be balanced against the possibility that premature discontinuation may occur. Premature discontinuation carries its own set of problems, including difficulty in reestablishing artificial airways and compromised gas exchange. It has been estimated that as much as 42% of the time that a medical patient spends on a mechanical ventilator is during the discontinuation process. This percent is likely to be much higher in patients with more slowly resolving lung disease processes.
There are a number of important issues involved in the management of a mechanically ventilated patient whose disease process has begun to stabilize and/or reverse such that the discontinuation of mechanical ventilation becomes a consideration. First, an understanding of all the reasons that a given patient required a mechanical ventilator is needed. Only with this understanding can medical management be optimized. Second, assessment techniques to identify patients who are capable of ventilator discontinuation need to be utilized. Ideal assessment techniques should be able to easily and safely distinguish which patients need prompt discontinuation and which need continued ventilatory support. Third, ventilator management strategies for stable/recovering patients who still require some level of ventilatory support need to be employed. These strategies need to minimize both complications and resource consumption. Fourth, extended management plans (including tracheotomy and long-term ventilator facilities) need to be considered for the long-term ventilator-dependent patient.
To address many of these issues, the Agency for Healthcare Policy and Research (AHCPR) charged the McMaster University Evidence Based Practice Center to do a comprehensive evidence-based review of many of the issues involved in ventilator weaning/discontinuation. Led by Deborah Cook MD, an exhaustive review of several thousand articles in the world literature resulted in a comprehensive assessment of the state of the literature in 1999. At the same time, the American College of Chest Physicians (ACCP), the Society for Critical Care Medicine (SCCM), and the American Association for Respiratory Care (AARC) formed a task force to produce evidence-based clinical practice guidelines for managing the ventilator-dependent patient during the discontinuation process. The charge of this task force was to utilize the McMaster AHCPR report as well as their own literature review to address the following 5 issues: (1) the pathophysiology of ventilator dependence; (2) the criteria for identifying patients who are capable of ventilator discontinuation; (3) ventilator management strategies to maximize discontinuation potential; (4) the role of tracheotomy; and (5) the role of long-term facilities. Review/writing teams were formed for each of these issues.
From these evidence-based reviews, a series of recommendations were developed by the task force, which are the basis of this report. Each recommendation is followed by a review of the supporting evidence, including an assessment of the strength of the evidence (Table 1). As there were many areas in which evidence was weak or absent, the expert opinion of the task force was relied on to “fill in the gaps.” Consensus was reached, first, by team discussions and, later, through the repeated cycling of the draft through all members of the task force.
Both the McMaster AHCPR group and the task force recognized the needs for the future. These include more randomized controlled trials to look at a number of issues. Among the more important questions that need answering are the following: (1) Which criteria are the best indicators of reversal of respiratory failure in the screening process? (2) What factors are involved in ventilator dependence and which measurement techniques are most useful in determining ultimate success in the discontinuation process? (3) In balancing discontinuation aggressiveness against the risks of premature discontinuation, what is a reasonable reintubation rate in patients recently removed from ventilatory support? (4) What is the value of trying to reduce levels of partial ventilator support in stable/recovering patients who have failed a discontinuation assessment? (5) What role do tracheotomies have in facilitating the discontinuation process? (6) What is the role of the long-term facility, and when should patients be transferred to such facilities?