ARDS : early diagnosis & prevention of irreversible change by surfactant therapy

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(1) Determination of the reversible period in adult (acute) respiratory distress syndrome (ARDS) : In experiment to administrate endotoxin, elastase, lysolecithin, and anti-surfactant protein B monoclonal antibody in rats and rabbits, the ARDS-like symptom could be reversed by surfactant replacement until 6 hours after the arterial oxygen pressure (PaO_2) started to decrease. Therefore, 6 hours after the onset of the symptom was thought to be the reversible period. Formation of hyaline membrane, however, was noted in the alveoli even at the reversible period, uggesting that some cares should be taken to prevent the organic changes as early as possible.(2) Replacement method of surfactant and development of artificial surfactant : In rats, inhalation of an aerosolized surfactant (modified natural surfactant, Surfactant CK) reversed symptoms of ARDS-like lung injury which was induced by administration of endotoxin. By this procedure, the organic change of the lung tissue, an irreversible damage, could be postponed at least for 6 hours. In addition, an artificial surfactant which was prepared with synthetic dipalmitoyl-phosphatidylcholine, phosphatidylglycerol and dioleoylphosphatidylcholine (60 : 20 : 20) plus surfactant protein B (0.7%) and C (1.4%) exhibited the same effects with Surfactant CK.(3) Relation between condition of pulmonary surfactant and vascular resistance : We found that inactivation of pulmonary surfactant induces dilatation of the capillary vessels of the alveoli. We think that this is an important finding to explain the mechanism of hypoxemia in ARDS.(4) Early diagnosis of ARDS : We have obtained some findings that surface tension values of the liquid aspirated from the trachea may by useful for early diagnosis of ARDS.