Influence of direct and indirect etiology on acute outcome and 6-month functional recovery in acute respiratory distress syndrome

Abstract

To assess the possibility that acute respiratory distress syndrome (ARDS) of pulmonary and nonpulmonary origins represent two distinct syndromes. Analysis of data collected prospectively from an inception cohort of 117 patients with ARDS. Adult intensive care unit (ICU), university/postgraduate hospital. Differences were sought in mortality and 6-month functional outcome between patients developing ARDS due to pulmonary (group 1) and nonpulmonary (group 2) pathology. Group 1 patients displayed a trend toward increased ICU and in-hospital mortality (42.1% vs. 23.2%, p = .10, and 47.4% vs. 27.9%, p = .11, respectively). No difference was found in ICU length of stay (46.3 +/- 4.9 vs. 39.0 +/- 4.8 days for groups 1 and 2, respectively) nor in duration of positive-pressure ventilation (26.2 +/- 4.3 vs. 20.6 +/- 3.2 days). However, the need for pressure-controlled inverse ratio ventilation was significantly greater in group 1 (16.9 +/- 3.2 vs. 9.1 +/- 1.3 days; p = .033). In survivors, reductions in total lung capacity at 6 months (68.1 +/- 4.6 vs. 61.8 +/- 4.6% predicted for groups 1 and 2, respectively; p = .4), accessible lung volume (74.4 +/- 4.4 vs. 68.9 +/- 4.9% predicted; p = .56), and forced expiratory volume (77.8 +/- 2.9 vs. 80.3 +/- 2.4% predicted; p = .57) did not differ between groups. Gas transfer coefficient was well preserved (84.5 +/- 4.6 vs. 86.6 +/- 4.7% predicted; p = .80). These data suggest a trend toward higher mortality and ventilatory requirements in ARDS of direct etiology, generating a hypothesis worthy of further exploration.