Review: Continuous positive airway pressure support reduces the need for intubation in patients with cardiogenic pulmonary edema
ACP J Club. 1999 May-June;130:58. doi:10.7326/ACPJC-1999-130-3-058
Pang D, Keenan SP, Cook DJ, Sibbald WJ. The effect of positive pressure airway support on mortality and the need for intubation in cardiogenic pulmonary edema. A systematic review. Chest. 1998 Oct;114:1185-92.
Is continuous positive airway pressure (CPAP) or noninvasive positive-pressure ventilation (NIPPV), used in conjunction with standard medical care, effective for reducing mortality and the need for endotracheal intubation in patients who are hospitalized with cardiogenic pulmonary edema and have abnormal gas exchange values?
Studies were identified through MEDLINE (1983 to June 1997) using terms related to the therapy of pulmonary edema and respiratory insufficiency. Bibliographies of relevant studies and review articles were reviewed, and conference abstracts from 9 relevant journals were searched.
English-language, randomized controlled trials (RCTs) were selected if the patients had presented to the hospital with acute pulmonary edema; if either CPAP and standard medical care or NIPPV and standard medical care were compared with standard medical care alone; and if the outcomes were hospital survival or need for endotracheal intubation.
Data were extracted on study quality and characteristics, sample size, nationality of the study, inclusion and exclusion criteria, intervention, and outcomes.
497 articles were reviewed, and 3 studies met the inclusion criteria. CPAP was evaluated in all 3 studies (179 patients). CPAP plus usual care compared with usual care alone reduced the need for intubation but not mortality (Table). Insufficient data were available for meaningful assessment of NIPPV because no RCTs of NIPPV and usual care were found. One small RCT of NIPPV and CPAP was found, but it included no control patients and the groups were not similar at baseline.
Continuous positive airway pressure plus usual care in patients with cardiogenic pulmonary edema reduces the need for endotracheal intubation but does not clearly show a reduction in mortality. Inadequate evidence exists to evaluate noninvasive positive-pressure ventilation.
Sources of funding: Richard Ivey Critical Care Trauma Center; London Health Sciences Centre; University of Western Ontario; Aberdeen Medical School.
For correspondence: Dr. S.P. Keenan, St. Paul's Hospital, 1081 Burrad Street, Vancouver, British Columbia V6Z 1Y6, Canada. FAX 604-631-5674.
Table. Continuous positive airway pressure (CPAP) plus usual care vs usual care alone for patients with cardiogenic pulmonary edema*
|Outcomes at discharge||Weighted event rates||RRR (95% CI)||NNT (CI)|
|Need for intubation||15.0%||41.1%||61% (34 to 77)||4 (3 to 7)|
|Mortality||11.2%||17.8%||43% (-21 to 73)||Not significant|
*Abbreviations defined in Glossary; RRR, NNT, and CI calculated from data in article.
Technological advances often outstrip our ability to produce scientific studies. The use of CPAP, the modality on which Pang and colleagues base their conclusions, has in many institutions already been supplanted by the use of nasal or full-face mask biphasic intermittent positive airway pressure ventilation (BiPAP) and various modes of NIPPV. This supplantation is largely because of clinical experience showing improved tolerance, comfort, and efficacy despite a dearth of hard data, as the authors have shown.
Pang and colleagues have valiantly attempted to clear some very muddy waters in the burgeoning practice of noninvasive modes of ventilatory assistance. They have focused their review on cardiogenic pulmonary edema and, because of the nature of research in such a varied field of practice, were only able to find 3 studies that met their review criteria on the use of CPAP. Many other studies that did not meet their criteria variously used nasal or full-face mask BiPAP, ventilator-supplied CPAP with or without pressure support ventilation, or intermittent mandatory ventilation and were generally clinical series or case reports. The authors' conclusions are appropriately modest, and they make 2 important points. First, the 3 studies of CPAP showed a 26% absolute risk reduction for intubation, and “this suggests that 4 patients with acute pulmonary edema eligible for CPAP would need to be treated with CPAP to prevent 1 endotracheal intubation.” Second, “Patients should become more comfortable as evidenced by a drop in heart rate, respiratory rate, and improvement in gas exchange values. If this does not occur early, consideration should be given to intubation and mechanical ventilation.” This is, indeed, rational clinical practice: First, expect failure at least half of the time. Second, if the first mode of support chosen, such as nasal BiPAP, does not produce clinical improvement fairly quickly, try another mode, such as full-face mask BiPAP or CPAP with or without pressure support ventilation. Finally, if success still has not been achieved, use conventional therapy.
Christopher M. Hughes, MD
Monongahela Valley HospitalMonongahela, Pennsylvania, USA
Christopher M. Hughes, MD
Monongahela Valley Hospital
Monongahela, Pennsylvania, USA