Noninvasive positive pressure ventilation (NPPV) is a life-saving procedure in acute respiratory failure (ARF), but its technique is not yet in routine use in many respiratory centers. We carried out a prospective randomized study comparing the combination of NPPV with conventional therapy (oxygen, bronchodilators, steroids, and theophylline) with conventional therapy alone in patients with acute respiratory failure caused by exacerbation of chronic obstructive pulmonary disease (COPD). A total of 58 patients were recruited from a large group of patients admitted to our hospital between September 1995 and March 1997. Twenty-nine patients were randomly assigned to the NPPV group and 29 to the conventional (non-NPPV) group. The patients were matched for demographic and physiological norm values (mean age 63.4 +/- 5.5 vs. 66.2 +/- 7.1 years, mean FEV1 0.68 +/- 0.15 vs. 0.74 +/- 0.16 L, PaO2 51.4 +/- 6.8 vs. 52.3 +/- 6.5 mm Hg, PaCO2 63.4 +/- 10.9 vs. 64.9 +/- 9.7 mm Hg, and pH 7.28 +/- 0.07 vs. 7.26 +/- 0.06). The outcome end points were needed for endotracheal intubation, length of hospital stay, and incidence of complications. NPPV was administered using BiPAP ventilatory device (Respironics, Inc.) by spontaneous and spontaneous/timed modes via nasal and facial masks. The mean time of NPPV was 29 +/- 25 h. Three patients refused from NPPV because of intolerance of mask or ventilation procedure. Two of them were eventually intubated and one of them died. In patients administered NPPV, we observed a significant rise of pH and fall of PaCO2 after 1 h of ventilation, in contrast to the non-NPPV group (7.34 +/ 0.09 vs. 7.21 +/- 0.08, p < 0.05; 53.2 +/- 10.7 vs. 71.4 +/- 10.2 mm Hg, p < 0.01, respectively). The need in intubation was lower in the NPPV group as compared to the reference group (12 vs. 28%, p = 0.18), mortality rate was higher in the non-NPPV group (31 vs. 8%, p = 0.03), and hospital stay was shorter in NPPV patients (26 +/- 7 vs. 34 +/- 10 days). The incidence of complications was lower in the NPPV group, they were less significant, and did not involve discontinuation of ventilation. Hence, NPPV is a first-line therapy in patients with ARF caused by COPD exacerbation, due to obvious advantages over conventional methods of treatment.