Missed Opportunities for Noninvasive Ventilation in Acute Respiratory Failure
Abstract & Commentary
By David J. Pierson, MD, Editor, Professor, Pulmonary and Critical Care Medicine, Harborview Medical Center, University of Washington, Seattle, is Editor for Critical Care Alert.
Synopsis: In this review of patients admitted to the ICU with acute respiratory failure secondary to COPD exacerbation or cardiogenic pulmonary edema, nearly two-thirds of patients who apparently met criteria for noninvasive ventilation (NIV) were intubated without a trial of NIV.
Source: Sweet DD, et al. J Crit Care. 2008;23:111-117.
Investigators at St Paul's Hospital in Vancouver, BC, conducted a retrospective review of all ICU admissions between November 1998 and July 2003, to find all patients who were potential candidates for noninvasive ventilation (NIV) in the context of an exacerbation of COPD or acute cardiogenic pulmonary edema (CPE). They sought patients with these admitting diagnoses who were able to cooperate, protect their airways, and clear secretions; who had respiratory rates between 26 and 35 breaths/min; who had arterial pH < 7.35, PCO2 > 50 mm Hg, or PO2 < 60 mm Hg (if an arterial blood gas was obtained); and who had no contraindication to NIV. The purpose of the study was to determine how many of the identified patients were given a trial of NIV, under these circumstances in which that intervention could be considered appropriate therapy.
During the study interval 243 patients were admitted to the ICU with either COPD exacerbation or acute CPE, and received ventilatory assistance either via an endotracheal tube or with NIV. After exclusion of patients who were intubated prior to admission or for surgery, had incomplete records, or had identifiable contraindications to the use of NIV, there were 59 patients (44 COPD, 15 CPE) who were considered NIV candidates. Of these, only 20 (34%; 16 COPD and 4 CPE) were given a trial of NIV prior to intubation. Eleven of these 20 patients failed the NIV trial and were subsequently intubated. There were no detectable changes in the use of NIV or in its success rate during the years encompassed by the study. The authors conclude that, although there could have been inapparent or unrecorded reasons why NIV should not have been used in some of the directly intubated patients, the fact that nearly two-thirds of this cohort who appeared to be appropriate for this therapy did not receive it represents a missed opportunity for potentially life-saving treatment, and a potential focus for increased efforts at knowledge translation via education and care standardization.
Commentary
Currently assuming increasing prominence along with evidence-based medicine in the quest for better health care outcomes is the concept of knowledge transfer.1 It is being increasingly recognized that knowledge of the best therapy for a given condition (eg, through the results of randomized controlled clinical trials) takes us only part way to the desired end results of decreased mortality, reduced complications, shortened hospital stays, and improved quality of life for our patients. That knowledge has to be put into use. Noninvasive ventilation can achieve all the positive results just listed in patients with COPD exacerbations or CPE, but only if it is used when it should be and in an effective manner.
In this study, Sweet and colleagues found that, in their institution and between 1998 and 2003, NIV had neither been used as often as it should have been nor (one can infer) as effectively as it should have been. Because of the limitations of a retrospective study design, we cannot know which of their patients had contraindications to NIV that were not picked up in the chart review. However, it seems unlikely that such contraindications were present in two-thirds of the patients who were otherwise identified as good candidates for NIV. And the fact that 11 of the 20 patients in whom NIV was tried subsequently needed intubation suggests that the application of NIV may not have been optimal. In numerous studies of NIV in acute respiratory failure caused by COPD exacerbation, avoidance of intubation has been achieved in at least three-fourths of the patients, with roughly similar results in studies of CPE.2,3
There is definitely a learning curve with NIV. As clinicians and institutions gain more experience, the use of NIV tends to increase, as do success rates such as in the avoidance of intubation. Although Sweet et al did not find evidence of a secular trend of increasing NIV use during the 6-year period of their review, with increases in both the evidence base and clinician experience with NIV since 2003 it may be assumed that this therapy is finding wider and more successful application today in the authors' institution as elsewhere.
The evidence base supporting the use of NIV in acute respiratory failure, and defining the clinical settings in which it can and cannot improve patient outcomes, has become much more solid during the last decade.2,3 The table below lists the conditions in which experience with NIV has been most extensive, arranged according to the degree to which the supporting evidence is most firm.
References
- Sinuff T, et al. Crit Care Med. 2008 Apr;36(4):1049-1058.
- Hill NS, et al. Crit Care Med. 2007;35(10):2403-2407.
- Peñuelas O, et al. Noninvasive positive-pressure ventilation in acute respiratory failure. CMAJ. 2007;177(6):1211-1218.
- Curtis JR, et al. Crit Care Med. 2007 Mar;35(3):932-939.
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