Non invasive ventilation in acute respiratory insufficiency: an alternative.

Effectiveness of non invasive positive pressure ventilation (NIPPV) was pro spectively evaluated in 22 selected patients with acute respiratory failure , meeting criteria for orotracheal intubation and conventional mechanical v entilation. Patients were divided in two groups: group A (17 patients) with initial PaCO2 above 45 mm Hg and group B (5 patients) with initial PaCO2 b ellow 45 mmHg. NIPPV was administered with 2 levels of pressure either by n asal or facial mask. Respiratory rate (RR), arterial blood pH, PaCO2 and Pa O2/FiO(2) were registered pretreatment, 1 hour and 24 hours after NIPPV. St atistical analysis was performed by ANOVA test, p < 0.05 was considered sig nificant. Results: In group A there was a reduction in RR (X +/- DS) from 3 1.2 +/- 8.2 to 24.7 +/- 8.2 at one hour (h) (p = 0.02) and to 23.4 +/- 6.5 at 24 hs (p = 0.01), pH change from 7.33 +/- 0.07 to 7.37 +/- 0.07 at one h our (p = 0.13) and to 7.40 +/- 0.07 at 24 hs (p = 0.01), a PaCO2 change fro m 69.5 +/- 19.6 to 57.8 +/- 16.9 at one hour (p = 0.06) and to 54 +/- 13 at 24 hs (p = 0.02), and PaO2/FiO(2) change from 187.3 +/- 60.2 to 223.9 +/- 6.5 at one hour (p = 0.12) and to 245.8 +/- 75 at 24 hs (p = 0.03). In grou p B there was a change in RR from 33 +/- 16.3 to 26.6 +/- 12.5 at one hour (p = 0.46) and to 21.3 +/- 4.2 at 24 ha (p = 0.27), PaO2/FiO(2) change from 113.4 +/- 31 to 137.8 +/- 57.2 at one hour (p = 0.44) and to 208.7 +/- 51. 2 at 24 hs (p = 0.03). Only two patients in group A and one in group B were converted to conventional ARM. Conclusion 1) NIPPV is a therapeutic altern ative for selective patients with acute respiratory insufficiency and may r educe known morbidity of conventional mechanical ventilation. 2) In the gro up with hypercapnic acute respiratory failure the improvement in respirator y function begins with an immediate reduction in RR. Significant improvemen t in arterial blood gases usually occurs within 24 hours of NIPPV.