Noninvasive positive pressure ventilation in acute respiratory failure due to COPD vs other causes: Effectiveness and predictors of failure in a respiratory ICU in North India

OBJECTIVES: To determine the effectiveness of noninvasive positive pressure ventilation (NIPPV), and the factors predicting failure of NIPPV in acute respiratory failure (ARF) due to chronic obstructive pulmonary disease (COPD) versus other causes of ARF. PATIENTS AND METHODS: This was a prospective observational study and all patients with ARF requiring NIPPV over a one-and-a-half year period were enrolled in the study. We recorded the etiology of ARF and prospectively collected the data for heart rate, respiratory rate, arterial blood gases (pH, partial pressure of oxygen in the arterial blood [PaO(2)], partial pressure of carbon dioxide in arterial blood [PaCO(2)]) at baseline, one and four hours. The patients were further classified into two groups based on the etiology of ARF as COPD–ARF and ARF due to other causes. The primary outcome was the need for endotracheal intubation during the intensive care unit (ICU) stay. RESULTS: During the study period, 248 patients were admitted in the ICU and of these 63 (25.4%; 24, COPD–ARF, 39, ARF due to other causes; 40 male and 23 female patients; mean [standard deviation] age of 45.7 [16.6] years) patients were initiated on NIPPV. Patients with ARF secondary to COPD were older, had higher APACHE II scores, lower respiratory rates, levels compared to other causes of ARF. After one hour there was lower pH and higher PaCO(2) levels with increase a significant decrease in respiratory rate and heart rate and decline in PaCO(2) levels in patients successfully managed with NIPPV. However, there was no in pH and PaO(2) difference in improvement of clinical and blood gas parameters between the two groups except at one hour which was significantly the rate of decline of pH at one and four hours and PaCO(2) faster in the COPD group. NIPPV failures were significantly higher in ARF due to other causes (15/39) than in ARF–COPD (3/24) (p = 0.03). The mean ICU and hospital stay and the hospital mortality were similar in the two groups. In the multivariate logistic regression model (after and adjusting for gender, APACHE II scores and improvement in respiratory rate, pH, PaO(2) at one hour) only the etiology of ARF, ie, ARF–COPD, was associated with a decreased PaCO(2) risk of NIPPV failure (odds ratio 0.23; 95% confidence interval, 0.58–0.9). CONCLUSIONS: NIPPV is more effective in preventing endotracheal intubation in ARF due to COPD than other causes, and the etiology of ARF is an important predictor of NIPPV failure.