Non-invasive ventilation in acute or chronic respiratory failure: a comparison of volumetric ventilation.

Background: Although experience acquired with non-invasive ventilation is r ecent, it is often proposed in selected patients with acute respiratory fai lure occurring in a background of chronic airflow obstruction Barometric or volumetric techniques can be used. Patients and methods. We compared tolerance and efficacy of inspiration ass ist (IA) using a present pressure and volume-controlled ventilation (VC). T welve patients with chronic airflow obstruction were randomized to IA (n=7) or VC (n=9) mode and ventilated with the appropriate mask. Results: Tolerance was equivalent for the two groups although hypercapnia f ell more in the IA group, particularly after 24 it ventilation (p<0.03), af ter three days (p<0.05), and at complete weaning (p<0.03). Correction of pH was significantly more rapid in the IA group than in the VC group (p<0.05 at 24 it). There was no difference in the number of days of ventilation, to tal ventilation,a time, or length of hospital stay. Success of non-invasive ventilation, defined as the control of acute respiratory failure without r ecourse to endotracheal :ventilation, was similar in the two groups (86% in group IA and 60% in group VC). Two of the 5 patients in the VC group:and o ne of the 7 in the IA group, required intubation.