[Problems in noninvasive positive pressure ventilation of patients with acute-on-chronic hypercapnic respiratory failure].

In patients with acute exacerbations of chronic obstructive pulmonary disease non-invasive positive pressure ventilation (NPPV) has been used to avoid endotracheal intubation. The aim of this study was to identify factors that can prevent the success of this technique. We applied a BiPAP ventilatory assist device (Respironics, Inc., Murrysville, PA) via a nasal mask to 13 patients with acute exacerbation of chronic respiratory failure and analyzed their clinical and physiological status. Intubation was not needed in 11 of 14 episodes (78%). The mean pH, PaCO2, and heart rate before BiPAP in the three patients who required intubation differed significantly from those in the patients who did not require intubation (pH 7.19 vs. 7.31: p < 0.05, PaCO2 107.8 vs. 77.8 Torr: p < 0.05, heart rate 127 vs. 105/min; p < 0.05). In those who required intubation the mean pH improved during the first 12 hours of BiPAP but then worsened. In 5 episodes, the PaCO2 increased during the initial trial of BiPAP, but decreased after the amount of supplemental oxygen was reduced. We conclude that NPPV should be used soon after respiratory failure begins, and care should be taken not to supply too much oxygen.