[Show abstract][Hide abstract]ABSTRACT: In acute respiratory distress syndrome, mechanical ventilation often induces alveolar overdistension aggravating the primary insult. To examine the mechanism of overdistension, surfactant-deficient immature rabbits were anesthetized with pentobarbital sodium, and their lungs were treated with serum-diluted modified natural surfactant (porcine lung extract; 2 mg/ml, 10 ml/kg). By mechanical ventilation with a peak inspiration pressure of 22.5 cm H2O, the animals had a tidal volume of 14.7 ml/kg (mean), when 2.5 cm H2O positive end-expiratory pressure was added. This volume was similar to that in animals treated with nondiluted modified natural surfactant (24 mg/ml in Ringer solution, 10 ml/kg). However, the lungs fixed at 10 cm H2O on the deflation limbs of the pressure-volume curve had the largest alveolar/alveolar duct profiles (> or =48,000 microm2), accounting for 38% of the terminal air spaces, and the smallest (<6,000 microm2), accounting for 31%. These values were higher than those in animals treated with nondiluted modified natural surfactant (P <0.05). We conclude that administration of serum-diluted surfactant to immature neonatal lungs leads to patchy overdistension of terminal air spaces, similar to the expansion pattern that may be seen after dilution of endogenous surfactant with proteinaceous edema fluid in acute respiratory distress syndrome.
Article · Nov 2004 · Journal of Applied Physiology
[Show abstract][Hide abstract]ABSTRACT: Surfactant therapy for acute respiratory distress syndrome (ARDS) has shown encouraging results in animal studies, but not always in clinical trials. Efficacy of this therapy may be limited to ARDS caused by indirect injury, but mistiming of its application in clinical trials may be responsible for the discouraging results. In addition, the therapy may not last long enough to be effective. In rats with acidified milk aspiration, the effects of aerosolized surfactant therapy followed by inhalation of aerosolized dextran (molecular weight, 40,000) last significantly longer than those of aerosolized surfactant therapy alone. This mode of surfactant therapy could lead to better results since it can be started and repeated at any time.