ARDS: refinement of concept and redefinition.

Abstract

AMERICAN REVIEW OF RESPIRATORY DISEASE who wrote Adult Respiratory Distress Syndrome (May it Rest in Peace) (2). In the interim, we have each continued both clinical and basic research designed to unravel some of the many remaining mysteries about the pathogenesis of ARDS and factors associated with the prognosis. Gradually, a fairly standard approach to supportive therapy has emerged that involves mechanical ventilation, use of positive end expiratory pressure (PEEP), blood and fluid replacement, treatment ofpresumed or identified infections, and nutritional and psychological support. Still today more than 50070 ofpatients die ofARDS in either the early or late stages of disease. Also this interval has seen the definition of many of the risk factors associated with ARDS (3, 4) and the factors associated with prognosis once ARDS is established (5). On the bright side is the favorable outcome of patients who can be weaned from mechanical ventilation and can leave the hospital (6). Those investigators who have continued to observe their patients over many years have marvelled at the potential of the lung to remodel itself and reestablish good or even normal ventilatory and gas transfer function of the lung. Many patients have minimal or no symptoms at all in the late recovery phase. The expanded definition of the adult respiratorydistress syndrome proposed by John Murray and associates in this issue has considerable merit in my opinion (7). Wecertainly need a grading system for severity of lung injury. Stratifying patients by the degree of impaired oxygenation along with PEEP requirements is both reasonable and practical. It will be potentially useful to identify causal factors related to the initiation of this syndrome. I am personally delighted at the suggestion that ARDS not be defined in terms of measurements made by a flow-directed catheter. After all, the flow-directed catheter didn't even exist when we offered our three early papers on ARDS (8-10). Certainly hemodynamic measurements will play a strategic role in selected patients as a guide to therapy and for clinical research purposes in certain patients with informed consent. I believe stratification by bedside measurements of overall compliance is also reasonable and practical. These measurements will be available and can be made serially in all patients requiring mechanical ventila-