Alveolar hyperoxic injury in rabbits receiving exogenous surfactant

We have previously demonstrated that instillation of a calf lung surfactant extract (CLSE) in rabbits after exposure to 100% O2 for 64 h mitigates the progression of lung pathology after return to room air (J. Appl. Physiol. 62: 756-761, 1987). In the present study, we investigated whether we could prevent or reduce the onset and development of hyperoxic lung injury by sequential instillations of CLSE during the hyperoxic exposure. Rabbits were exposed to 100% O2. CLSE (125 mg, approximately 170 mumol of phospholipid) was suspended in 10 ml of sterile saline and instilled intratracheally into their lungs, starting at 24 h in O2, a time at which no physiological or biochemical injury was detected, and at 24-h intervals thereafter. Control rabbits breathed 100% O2 and received either equal volumes of saline or no instillations at all. CLSE-instilled rabbits had higher arterial PO2 (Pao2) values throughout the exposure period and survived longer when compared with saline controls [120 +/- 4 vs. 102 +/- 4 (SE) h; n greater than or equal to 10; P less than 0.05]. At 72 h in O2, CLSE-instilled rabbits had significantly higher lavageable alveolar phospholipid levels (12.5 +/- 1.5 vs. 5 +/- 1 mumol/kg) and total lung capacities (41 +/- 2 vs. 25 +/- 3.5 ml/kg) and lower levels of alveolar protein (24 +/- 3 vs. 52 +/- 8 mg/kg), minimum surface tension (2 +/- 1 vs. 26.1 dyn/cm), and lung wet-to-dry weights (5.9 +/- 0.2 vs. 6.5 +/- 0.3). After 72 h in O2, lungs from both CLSE- and saline-instilled rabbits showed evidence of diffuse hyperoxic injury. However, atelectasis was less prominent in the former. We concluded that instillation of CLSE limits the onset and development of hyperoxic lung injury to the alveolar epithelium of rabbits.