Outcomes of Noninvasive Ventilation in Acute Hypoxemic Respiratory Failure in a Respiratory Intensive Care Unit in North India

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.