Surfactant and adult respiratory distress syndrome

In order to determine if the Adult Respiratory Distress Syndrome (ARDS) is associated with a shortage of pulmonary surfactant, we have examined a series of 155 undiluted tracheal aspirates obtained from 23 patients with ARDS and from 30 patients without ARDS, all 53 needing ventilatory support. The unfixed and unstained specimens were examined by polarized light microscopy for the presence of pulmonary surfactant. Free surfactant particles were present in the aspirates of 50 patients (95%). Within minutes of obtaining the specimen, in addition to showing surfactant, the examination of these undiluted, unfixed tracheal aspirates by light microscopy showed the presence of bacterial and fungal infection. As fibrinogen/fibrin inactivates surfactant, the undiluted aspirates of 21 patients with ARDS and of 30 patients without ARDS were stained for the presence of these proteins by a new slide method using 0.01 ml of tracheal aspirate. Fibrinogen/fibrin was found in the aspirates from 20 of 21 patients with ARDS and in only five of 30 patients without ARDS; these five had bronchopneumonia. The method has a sensitivity of 0.95 and a specificity of 0.83. The role of plasma proteins and of neutrophil leucocytes in causing ARDS is discussed.