We treated prematurely delivered rabbit pups with the synthetic
surfactant that has been named
Exosurf. By weight,
Exosurf is 61.8%
dipalmitoylphosphatidylcholine, 6.8% hexadecanol, 4.6%
tyloxapol, and 26.7% NaCl. This simple mixture, suspended at 15 mg
lipid X ml-1 water, has appropriate in vitro characteristics for a lung
surfactant substitute. As determined by static pressure volume relationships performed after 30 min ventilation, lungs treated with
Exosurf accepted significantly more gas at maximal inflation (36 versus 15 ml X kg-1
body weight) and had significantly greater volumes during deflation that did saline-treated control lungs; lungs treated with natural rabbit
surfactant (SAM) had significantly larger volumes at maximal inflation (65 versus 35 ml X kg-1) and during deflation than did the
Exosurf-treated lungs. After 30 min of ventilation with
oxygen and fixation
at 10 cm H2O pressure, the ratio of air space to tissue space was determined by a point-counting technique, and mean linear intercepts were measured for air spaces.
Exosurf-treated lungs were intermediate between SAM and saline-treated lungs in both measurements. With
positive pressure ventilation to maintain a tidal volume of 6.5 to 7.5 ml X kg-1, total compliance was significantly greater and inspiratory pressure significantly lower in both SAM- and
Exosurf-treated animals than in saline-treated control animals, although the lungs of the SAM-treated animals were more compliant than the lungs of animals treated with
Exosurf. During the first minute of
positive pressure ventilation, lungs treated with SAM or
Exosurf expanded equally rapidly, both expanding more rapidly than the saline-treated lungs.(ABSTRACT TRUNCATED AT 250 WORDS)