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Source: Delclaux C, et al. Treatment of acute hypoxemic non-hypercapnic respiratory insufficiency with continuous positive airway pressure delivered by a face mask. JAMA 2000;284:2352-2360.
This multicenter, prospective, randomized trial compared the efficacy of continuous positive airway pressure (CPAP) plus oxygen to standard oxygen therapy (O2 alone) in 123 intensive care unit (ICU) patients with acute respiratory insufficiency. At study entry, all patients had bilateral infiltrates on chest x-ray, and 17% were classified as pure cardiac decompensation; 83% had acute lung injury due to infections, adult respiratory distress syndrome (ARDS), near drowning, and other causes.
CPAP treatment failed to reduce the endotracheal intubation rate (34% CPAP vs 39% O2), hospital mortality (31% vs 30%) or median ICU length of stay (6.5 vs 6.0 days). A higher number of adverse events occurred with CPAP treatment (18 vs 6, P = 001). Four patients in the CPAP group experienced cardiac arrest; no cardiac arrests occurred in the oxygen alone group (P = 0.14).
This study helps further define the population in which non-invasive positive pressure ventilation (NPPV) should be considered. To date, the evidence supporting NPPV is strongest for patients with acute exacerbations of chronic obstructive pulmonary disease (COPD) with hypercarbia. In fact, in COPD patients, NPPV has been shown not only to decrease the need for intubation, but also has been associated with improved survival. The findings of several studies, including a related article in the Journal of the American Medical Association, have suggested that the increased survival seen in COPD patients may be due, in part, to the avoidance of infectious complications, especially nosocomial pneumonia.1
However, this study raises some serious doubts as to the effectiveness of CPAP in patients with acute hypoxemic, non-hypercapnic respiratory failure primarily due to non-hydrostatic pulmonary edema. Not only was there no improvement in any of the main outcome measures for the CPAP group, but a significantly higher number of adverse events occurred with CPAP treatment. Most concerning, although alone not statistically significant, were the four cardiac arrests in the CPAP group that occurred at the time of intubation (3 patients), or at the time of removal of the CPAP mask for nursing care (1 patient). With the safety of CPAP in this group in question, it makes "just trying" NPPV an uncertain approach in these patients.
1. Girou E, et al. Association of noninvasive ventilation with nosocomial infections and survival in critically ill patients. JAMA 2000;284:2361-2367.