Predicting the presence of pulmonary function impairment in adult respiratory distress syndrome survivors.

Varying degrees of impairment in pulmonary function in survivors of adult respiratory distress syndrome (ARDS) have been reported. Physiologic indices of the severity of disease have been associated with impaired pulmonary function after ARDS, including duration of exposure to FIO2 > 0.6, AaDO2, maximal mean pulmonary artery pressure, lowest total static thoracic compliance, and peak airway pressure. Prediction of impairment following ARDS is difficult because clinical observations may reflect reversible lung injury (e.g. lung edema) and clinical features of ARDS do not predict subsequent function reliably. We developed a severity score to predict the presence of impairment of pulmonary function in 51 ARDS survivors, by examining the following clinical variables: (1) predisposing factor for ARDS; (2) age; (3) sex; (4) severity of hypoxemia; (5) smoking history; (6) number of days of positive pressure ventilation; (7) lowest total static thoracic compliance; (8) maximal mean pulmonary artery pressure, and (9) presence of barotrauma. Pulmonary function studies were performed at least 1 year after ARDS onset. The ARDSscore developed required only two variables: ARDSscorce = duration of positive pressure ventilation (days) minus lowest static thoracic compliance (ml/cm H2O). Significant correlations (p < 0.001) were found between linear regressions of percent predicted FEV1, FVC, TLC and DLCO against ARDSscore. ARDSscore > +20 predicted an 82% probability of impaired FEV1, FVC or TLC and a 100% probability of an impaired DLCO. We conclude that a score based upon duration of positive pressure ventilation and lowest static thoracic compliance predicts impaired pulmonary function more than 1 year after ARDS.