Noninvasive intermittent positive pressure ventilation (NIPPV) via a nasal or facial mask is an effective treatment of hypercapnic acute respiratory failure (ARF) caused by various diseases preventing endotracheal intubation (ETI) in 60-90% of patients. The technique can even be effective for routine care, using simplified ventilators, after adequate personnel training. In this study, the effectiveness, in a general respiratory ward under usual care, of NIPPV delivered by simplified ventilators via facial or nasal mask was evaluated in 40 patients with hypercapnic ARF (NIPPV group) and compared to 30 matched historical patients under conventional treatment (Conv group). Compared to conventional treatment, NIPPV was associated with a reduction in negative events such as ETI and mortality together (17% versus 60%, p = 0.0002), but not mortality alone (5% versus 13.5%, NS) or in the mean (+/- SD) length of the hospital stay (27.31 +/- 16.2 versus 27.5 +/- 20.5 days, NS). Patients treated with NIPPV, but not those treated conventionally, showed significant and rapid changes in arterial carbon dioxide tension (Pa,CO2) and pH between baseline and subsequent evaluation after 6 h, 1, 3 and 7 days and upon the discharge from hospital; in fact, in the NIPPV group after 6 h the arterial pH had risen from 7.30 +/- 0.062 to 7.35 +/- 0.066 and Pa,CO2 had decreased from 9.4 +/- 1.5 to 8.5 +/- 1.1 kPa. In the Conv group pH was stable at 7.29 and Pa,CO2 had risen from 9.39 +/- 1.8 to 9.43 +/- 1.6 kPa. In the NIPPV group no differences were found in the admission characteristics between patients successfully and unsuccessfully ventilated, although a significant improvement was observed after 1 h, for pH from 7.31 +/- 0.058 to 7.36 +/- 0.57 and Pa,CO2 from 9.2 +/- 1.3 to 8.3 +/- 1.3 kPa in successfully ventilated patients. In patients who failed to be ventilated with NIPPV pH worsened, from 7.26 +/- 0.069 to 7.24 +/- 0.078 and Pa,CO2 from 10.0 +/- 2.1 to 11.3 +/- 2.5 kPa. In conclusion, addition of noninvasive positive pressure ventilation delivered by nasal or face mask to conventional therapy, reducing the need for endotracheal intubation, may improve the management of patients with hypercapnic acute respiratory failure as compared to conventional therapy alone, even when instituted in a respiratory ward under usual care with simplified ventilators.