EARLY CHANGES IN LUNG-FUNCTION AND RESPONSE TO SURFACTANT REPLACEMENTTHERAPY

Dynamic respiratory system compliance (Cdyn) was measured in 44 preter m babies before, immediately after, and for 96 h following administrat ion of artificial surfactant (Exosurf). There was no significant chang e in Cdyn for the whole group over the entire study period. Subdivisio n into three groups on the basis of Cdyn prior to surfactant revealed a significant and sustained deterioration in lung function in those ba bies with the highest starting compliance and a significant and sustai ned improvement in those with the lowest compliance. Inspired oxygen a nd alveolar/arterial oxygen gradient also exhibited significant differ ences with least improvement in the babies with the best initial lung function and most improvement in the babies with worst initial lung fu nction. Despite clear initial differences in clinical status, neither long-term oxygen requirements nor the incidence of chronic lung diseas e differed significantly between the three groups. We conclude that th e response of an individual baby to the administration of surfactant i s, in part, determined by the lung function before surfactant is admin istered. Babies with higher initial lung compliance are more likely to deteriorate after administration and caution should be used before se lection of such babies for surfactant treatment.