Objectives: To determine the outcomes of noninvasive ventilation (NIV) and the factors associated with NIV failure in patients with acute hypoxemic respiratory failure (AHRF).
Methods: This was a prospective observational study and all patients with AHRF requiring NIV over a one-and-a-half-year period were enrolled in the study. We recorded the etiology of AHRF and prospectively collected the data for heart rate, respiratory rate, arterial blood gases (pH, P(aO2), P(aCO2)) at baseline, 1 hour, and 4 hours. The patients were further classified into 2 groups, based on the etiology of AHRF: either acute lung injury/acute respiratory distress syndrome [ALI/ARDS], or AHRF due to other causes. The primary outcome was the need for endotracheal intubation during the ICU stay.
Results: During the study period, 287 patients were admitted in the ICU, and of these 40 (13.9%) (21 ALI/ARDS, 19 AHRF due to other causes; 16 male, 24 female patients; mean +/- SD age 43.2 +/- 20.6 years) patients with AHRF were initiated on NIV. The baseline characteristics were similar in the 2 groups. After 1 hour there was a significant decrease in respiratory rate and heart rate, with increase in pH and P(aO2); however, there was no difference in improvement of clinical and blood-gas parameters between the 2 groups. The NIV failures, the mean ICU and hospital stay, and the hospital mortality were similar in the 2 groups. In the univariate logistic regression model the only factor associated with NIV failure was the baseline ratio of P(aO2) to fraction of inspired oxygen (P(aO2)/F(IO2)) (odds ratio 0.97, 95% confidence interval 0.95-0.99).
Conclusions: NIV should be judiciously used in patients with AHRF. A low baseline P(aO2)/F(IO2) ratio was associated with NIV failure.