Early Predictors of Success of Non-invasive Positive Pressure Ventilation in Hypercapnic Respiratory Failure

Abstract

To study the indication of NIPPV in patients with hypercapnic respiratory failure. To evaluate the clinical, laboratory and ventilatory parameters with respect to improvement or deterioration in general condition of the patient. To predict the outcome in the form of weaning from NIPPV or requirement of invasive ventilation. To compare APACHE II score with outcome. Non-invasive ventilation (NIV) is now being considered more as the respiratory support of choice for acute respiratory failure. In some patients, with acute hypercapnic respiratory failure, NIV is inadequate and invasive ventilation is required for the management of respiratory failure. Thus, the determination of early predictors of the success of non-invasive positive pressure ventilation (NIPPV) is important to identify the patients who are likely to benefit from it. This study was done to determine the early predictors of the success of NIPPV in hypercapnic respiratory failure. In the current hospital-based prospective observational study, 100 patients admitted with hypercapnic respiratory failure requiring ventilation therapy are included in the study. Baseline clinical (heart rate [HR] and respiratory rate [RR]), arterial blood gas (ABG) parameters (pH, pO2, and pCO2), and ventilatory parameters were recorded before the initiation of NIPPV. The above parameters were re-evaluated at 1, 4, and 24 h after initiation of NIPPV. Acute Physiology and Chronic Health Evaluation II (APACHE II) score was also calculated on admission and at the end of 24 h to compare with the outcome. Of the 100 patients, 73% of patients showed improvement in clinical and laboratory parameters. There was an improvement in HR, RR, pH, pCO2, and pO2 within the 1st hour and continued to improve even after 1 h, 4 h, and 24 h of NIPPV in the success group. About 27% of patients who failed to improve required intubation. The optimum cutoff value for APACHE II score on admission for predicting the outcome of NIPPV was found to be 33 in this study. Therefore, a score above 33 predicts failure of NIV. This study demonstrated that the clinical and laboratory parameters predict the success of NIPPV in patients with hypercapnic respiratory failure averting the need for mechanical ventilation.