THE PLEURAL EFFUSION IN ALI/ARDS PATIENTS: A CT SCAN STUDY

INTRODUCTION. The pleural effusion in patients with ALI/ARDS is a quite common finding. However, there are only few data which evaluated the presence/amount of pleural effusion and its clinical consequences. We aimed to compute the amount of pleural effusion and the impairment of gas exchange and the severity of lung disease. METHODS. Patients were studied at PEEP 5, 15 and 45 cmH2O of airway pressure during an end expiratory pause, by lung spiral CT scan (exposure 120 Kv-250 mA). Gas exchange was measured at the two PEEP levels. The outline of the lungs and of pleural effusion were manually delineated in each image by a physician using a dedicated software (Soft-EFilm University of Milan). Lung recruitability was computed as the fraction of total lung weight which regains inflation from 5 to 45 cmH2O of airway pressure. Patients were grouped according to the median value of the amount of pleural effusion. RESULTS. 68 ALI/ARDS patients mechanically ventilated (age 55±17 yrs, BMI 25±5 Kg/m2, PaO2/FiO2 200±77, PEEP 11.1±3.0 cmH2O, tidal volume 8.8±1.9 ml/Kg) were enrolled. The median pleural effusion was 293 ml (range 0-1023 ml). In table data are presented as mean ± SD. TABLE 1. Lower pleural effusion Higher pleural effusion PaO2 (mmHg) 79±21 80±26 PaCO2 (mmHg) 42±9 41±8 Age (yrs) 50±18 60±15 Lung weight (gr) 1560±515 1441±496 Lung recruitability (%) 13±10 13±13 p<0.05 vs Lower Effusion CONCLUSION. The presence of pleural effusion was not related to the impairment of gas exchange and to the amount of lung disease. Older patients presented a higher amount of pleural effusion probably due to a reduction of lymph drainage.