Study objective: To establish the natural history of lung injury in adult respiratory distress syndrome (ARDS) in terms of increased pulmonary vascular permeability. Secondly, to relate such changes to the number of neutrophils in bronchoalveolar lavage (BAL) and a clinical score of the severity of lung injury.
Design: Prospective, open.
Setting: Adult intensive care unit of a tertiary (national) referral hospital.
Patients: Fourteen patients meeting accepted diagnostic criteria for ARDS.
Interventions: Mechanical ventilatory support. Conventional intensive care and support for other failed organ systems as appropriate.
Measurements and results: Pulmonary vascular permeability was estimated using a dual isotope technique (protein accumulation index [PAI]), neutrophil numbers by BAL and the severity of ARDS by the lung injury score (LIS). The PAI and LIS were measured simultaneously on three occasions as far apart as possible during the course of the illness. A single BAL was performed immediately after one of the three PAI/LIS measurements, the precise timing being dictated by the clinical stability of each patient. Fourteen patients (8 male; age range, 19 to 69 years) were studied, 1.40 +/- 0.16, 11.36 +/- 1.79, and 20.90 +/- 2.30 days after the onset of ARDS (mean +/- SEM). Six patients died. The PAI (normal range, 0 to 1.0 x 10(-3)) was 2.81 +/- 0.39, 2.94 +/- 0.48, and 2.80 +/- 0.87; and LIS (severe injury > or = 2.5) was 2.18 +/- 0.25, 2.48 +/- 0.14, and 2.06 +/- 0.27, respectively. The BAL neutrophil content was 54.09 +/- 8.89. There were significant positive correlations between PAI and LIS (r = 0.73, p < 0.001) and PAI and BAL neutrophil content (r = 0.81, p < 0.001).
Conclusions: These data suggest that increased pulmonary vascular permeability persists throughout the course of ARDS and is related to a clinical score of injury severity and BAL neutrophil content.