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Review: Noninvasive positive-pressure ventilation reduces mortality and need for intubation in the intensive care unit

ACP J Club. 1998 Mar-April; 128:39. doi:10.7326/ACPJC-1998-128-2-039

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Noninvasive positive-pressure ventilation reduced the need for intubation in acute respiratory failure

Source Citation

Keenan SP, Kernerman PD, Cook DJ, et al. Effect of noninvasive positive pressure ventilation on mortality in patients admitted with acute respiratory failure: a meta-analysis. Crit Care Med. 1997 Oct;25:1685-92.



To determine, using meta-analysis, whether standard therapy plus noninvasive positive-pressure ventilation (NIPPV) reduces mortality and the need for endotracheal intubation in adults admitted to the intensive care unit with acute respiratory failure.

Data sources

Clinical trials were identified with MEDLINE (1966 to September 1995) using the terms respiratory insufficiency; respiratory failure; or lung disease, obstructive, combined with the terms ventilation, mechanical; ventilators; mechanical or intermittent positive pressure ventilation; or inspiratory positive pressure ventilation. SCISEARCH was used to identify cited studies, bibliographies of studies and review articles were checked, and authors were contacted.

Study selection

Randomized controlled trials were selected if the patients studied presented to the hospital with acute respiratory failure, the intervention included the addition of NIPPV, and mortality or the need for intubation was reported.

Data extraction

Data were extracted on study quality, country of study, inclusion and exclusion criteria, type of NIPPV, mortality, and need for intubation.

Main results

7 studies met the inclusion criteria. 4 studies included only patients with chronic obstructive pulmonary disease (COPD) (172 patients), 2 studies included mixed populations (73 patients), and 1 study excluded patients with COPD (41 patients). Type of NIPPV varied (volume ventilator vs pressure support and nasal vs face mask interface). Patients who received NIPPV had reduced mortality and need for intubation (5 studies for each outcome) (Table). Subgroup analysis showed larger reductions when only patients with COPD were analyzed (3 studies for each outcome).


Standard therapy plus NIPPV reduces mortality and the need for endotracheal intubation in adults in the intensive care unit with acute respiratory failure. The benefits are greater when only patients with COPD are analyzed; patients without COPD may need further study.

Source of funding: In part, Department of Critical Care Medicine, University of Western Ontario.

For article reprint: Dr. S.P. Keenan, Department of Medicine, London Health Sciences Centre, Victoria Campus, 375 South Street, London, Ontario N6A 4G5, Canada. FAX 519-667-6698.

Table. Noninvasive positive-pressure ventilation (NIPPV) vs no NIPPV*

Outcome NIPPV weighted EER No NIPPV weighted CER RRR (95% CI) Weighted ARR NNT (CI)
Death in all studies 13% 32% 71% (41 to 85) 19% 6 (4 to 13)
Intubation in all studies 41% 67% 41% (-6 to 67) 26% 4 (3 to 24)
Death in all COPD studies 7% 31% 69% (35 to 86) 24% 5 (3 to 13)
Intubation in COPD studies 24% 69% 65% (45 to 78) 45% 3 (2 to 4)

*COPD = chronic obstructive pulmonary disease. Other abbreviations defined in Glossary; RRR, ARR, NNT, and CI calculated from data in article.


Keenan and colleagues provide meta-analytic evidence that NIPPV for patients with exacerbations of COPD is beneficial. Why, then, do they recommend caution before using NIPPV in practice? The limitations of meta-analysis (an observational technique) include the limitations of the experiments (clinical trials) reviewed. Bias, which is particularly important in nonblinded technology trials such as these, should be minimized by defining objective, reproducible study end points and by ensuring standardized application of the experimental method. This may be particularly difficult in the urgent clinical setting.

Other strategies to minimize bias include external adjudication committees that use prespecified criteria to evaluate outcomes. In the trials summarized, the method of application of NIPPV, the type of interface, and method of titrating NIPPV were not always specified. In addition, no statements were made of how well the study protocols were used or whether co-interventions were controlled. One is left with a general uncertainty concerning both the details of the NIPPV intervention and the nonspecificity of “standard therapy” that was used.

Practical, widespread use of research evidence from randomized trials depends on additional factors, including individual patient characteristics, explicit and exportable methods, clinicians' familiarity with technology, and availability of the technology (1). NIPPV seems to be a reasonable early intervention in the management of patients with COPD who have acute exacerbations, but caution is well advised.

Alan H. Morris, MD
LDS HospitalUniversity of UtahSalt Lake City, Utah, USA

Alan H. Morris, MD
LDS HospitalUniversity of Utah
Salt Lake City, Utah, USA


1. Morris A. Algorithm-based decision making. In: Tobin M, ed. Principles and Algorithm Practice of Intensive Care Monitoring. New York: McGraw-Hill; 1998:1355-81.