Normalization of arterial blood gases after treatment of surfactant-deficient lambs with Tween 20

Pulmonary surfactant (PS) is capable of lowering surface tension at an air-water interface to less than 10 dynes/cm. This property of PS is believed to be important for normal lung function. We tested the detergent Tween 20, which cannot lower surface tension at an air-water interface to less than 25 dynes/cm, for its ability to promote reasonable gas exchange in surfactant-deficient lambs delivered prematurely at 120 to 124 days gestation. Lambs were treated at birth with 75 mM NaCl (control), 5% Tween 20 in 75 mM NaCl, or PS in 75 mM NaCl and placed on infant ventilators. Control lambs had poor oxygenation and were in respiratory failure at 30 min of age (arterial PCO2 of 75.8 +/- 11 mmHg (mean +/- SE)) despite peak inspiratory pressures (PIP) of 32 +/- 0.7 cm H2O. Pulmonary surfactant treatment allowed adequate ventilation with a PIP of 23.8 +/- 1.2 cm H2O. Tween treatment also allowed adequate ventilation with a PIP of only 27 +/- 1.3 cm H2O. Minimal surface tensions in alveolar washes of control and Tween-treated lambs were 28.7 +/- 1.3 and 26.7 +/- 2.3 dynes/cm, respectively, compared with less than 10 dynes/cm for PS-treated lambs. Thus, Tween 20 did not alter the alveolar wash minimal surface tension when compared with that of the control animals but it did significantly improve gas exchange and lung compliance.