Nasal mask ventilation (NMV) has been used successfully in chronic restrictive respiratory failure and more recently in acute exacerbations of chronic obstructive pulmonary disease (COPD). This study aimed to evaluate the possible role of NMV in acute respiratory failure (ARF) episodes when mechanical ventilation with endotracheal intubation is questionable. Thirty patients (age, 76 +/- 8.1 years) were treated by NMV during ARF episodes (COPD, 20; other chronic respiratory failure [CRF], 5; chronic heart failure [CHF], 4). All patients were hypoxemic (PaO2, 5.85 +/- 1.62 kPa) and hypercapnic (PaCO2, 8.63 +/- 1.89 kPa) with respiratory acidosis (pH, 7.29 +/- 0.08). In all cases, clinical or physiologic parameters indicated the need for mechanical ventilation, but endotracheal intubation was either not applied because of the age and the physiologic condition of the patients (17 cases) or was postponed (13 cases). NMV was performed using a volume-cycled ventilator and a customized nasal mask. Ventilation was continuous during the first 12 hours and the following nights and was then intermittent during the day. Twenty-one patients improved clinically, within a few hours. Progressive correction of arterial blood gases was observed: PaO2 increased during the first hour, but PaCO2 decreased more slowly. Eighteen patients were able to be successfully weaned from NMV. Twelve patients failed to improve despite NMV: eight of them died and four required endotracheal intubation. There was no difference in the success rate between patients in whom endotracheal ventilation was contraindicated or postponed. Clinical tolerance was satisfactory in 23 patients and poor in seven patients. A return to the respiratory condition was observed in the surviving patients with subsequent discharge from hospital. NMV therefore successfully treated respiratory distress initially in 60 percent of the 30 patients. These results suggest that NMV could be a possible alternative in the treatment of ARF, even in very ill patients, when endotracheal ventilation is controversial or not immediately required.