TREATMENT RESPONSES TO SURFACTANTS CONTAINING NATURAL SURFACTANT PROTEINS IN PRETERM RABBITS

The in vivo function of surfactants reconstituted using natural surfactant lipid and protein constituents was evaluated in 27-day-gestation preterm rabbits, The animals were treated with protein-free surfactant lipids (LH-20), LH-20 + 5% SP-A, LH-20 + 1% SP-B, LH-20 + 1% SP-C, LH-20 + 5% SP-A + 10/o SP-B + 1% SP-C (SP-ABC), natural sheep surfactant, or 4 ml/kg 0.45% NaCl (control) and then ventilated with tidal volumes of 8 ml/kg and 3 cm H2O positive end-expiratory pressure (PEEP). Ventilatory pressures (peak pressures minus PEEP) and dynamic compliances of the LH-20 + SP-C rabbits were greater (p < 0.01) than those of control, LH-20, and LH-20 + SP-A groups but lower (p < 0.05) than those in the LH-20 + SP-B, LH-20 + SP-ABC, and sheep surfactant groups. Recoveries of intravascular labeled albumin in the lungs were comparable in the LH-20 + SP-B, LH-20 + SP-C, LH-20 + SP-ABC, and sheep surfactant groups and less (p < 0.01) than in LH-20 + SP-A rabbits, which had lower (p < 0.05) recoveries than did the control and LH-20 groups. The postventilation pressure-volume curves for LH-20 + SP-B and LH-20 + SP-ABC rabbits had significantly lower opening pressures, larger maximal lung volumes, and larger retained volumes on deflation relative to the LH-20 + SP-C, LH-20, and control groups. The effects of ventilation style on the responses were assessed by ventilating another group of similarly treated rabbits with tidal volumes of 10 ml/kg and zero cm H2O PEEP Without PEEP, only sheep surfactant demonstrated effective responses. In vivo function of reconstituted surfactants containing SP-B was comparable to sheep surfactant, but, unlike natural surfactant, the activity was dependent upon a ventilation style using PEEP.