Factors affecting the outcome of non-invasive ventilation in acute respiratory failure with acidosis and mortality in a tertiary care hospital in Pakistan

Abstract

Background To identify the predictors of non-invasive ventilation (NIV) outcome at early (one-hour) and later (24-hours) time points in acute respiratory failure because of any respiratory illness to infer the factors determining later success despite early failure, and timely shifting to mechanical ventilation. Methods The study was carried out at an intensive care unit of a tertiary care hospital in Lahore, Pakistan. Adult patients of type II respiratory failure of any cause requiring NIV were enrolled in study. Arterial blood gases were measured at one-hour and 24-hours. Binary regression analysis was applied to find out the factors affecting outcome at one and 24-hours, and factors associated with mortality. Results Among 226 patients; 139 were males, 71%, 25%, and 4% had obstructive, restrictive disease, and infective etiology respectively. Overall mortality was 17%, highest (50%) mortality among the infective group than the obstructive (16%) and restrictive disease (11%) groups. An initial PO2 of > 65mmHg, FiO2 > 41% and white cell count > 11/mm³ were associated with higher mortality. NIV failure at one-hour was associated with an initial pH < 7.25,initial bicarbonate < 33 mg/dl, initial PO2 > 65mmHg, and one-hour pCO2 > 75mmHg. Predictors of NIV failure at 24-hours were an initial PO2 > 65mmHg, one-hour pH < 7.3, one-hour PCO2 > 75mmHg, 24-hour PCO2 > 60mm Hg, and inspiratory positive airway pressure < 20 cm of H₂O. Conclusion High PO2 and FiO2 were associated with both mortality and NIV outcome. Initial pH, HCO3, PCO2 and IPAP predicted timings and failure of NIV.