A comparative study of characteristics and outcome of patients with acute respiratory failure and acute on chronic respiratory failure requiring mechanical ventilation

Abstract

Background and Aims: Patients with respiratory failure requiring assisted ventilation form a large diagnostic group among critically ill patients. The outcome of patients with acute respiratory failure (ARF) as compared to those with acute on chronic respiratory failure (ACRF), may be different. The present study was designed to evaluate the clinical and acid base profile at presentation, hospital course and outcome in patients with ARF and ACRF requiring ventilatory support and to define factors that influence the outcome of these two groups of patients. Materials and Methods : Fifty patients with respiratory failure {ACRF (n=27) and ARF (n=23)} who required invasive mechanical ventilation, were included in a prospective fashion. Clinical data including APACHE II score, blood gas analysis and renal and liver functions were recorded at presentation and for the next three days. Survival to hospital discharge was the primary outcome measure. Various parameters were compared between ARF and ACRF, as well as between survivors and non-survivors to define predictors of mortality. Results: Patients with ARF were significantly younger (41.5 versus 64.4 years, P P P =0.009). For the whole study group, APACHE II score and serum creatinine, 48 hrs after admission, were independent predictors of mortality. Conclusions: Although patients with ARF and ACRF may appear equally ill at presentation, mortality is higher for patients with ARF. A higher incidence of complications such as development of non-pulmonary organ failure during the hospital course in patients with ARF, seems to be responsible for this increased mortality.