THE PHYSIOLOGICAL-EFFECTS OF SURFACTANT TREATMENT ON GAS-EXCHANGE IN NEWBORN PREMATURE-INFANTS WITH HYALINE-MEMBRANE DISEASE

To describe the physiologic effects of surfactant treatment on gas exc hange in human premature infants with hyaline membrane disease, functi onal residual capacity (FRC), tidal volume (V(T)), the alveolar portio n of tidal volume (V(A)), alveolar ventilation (V(A)), nitrogen cleara nce index, effective breath fraction calculated as V(A)/V(T), complian ce of the respiratory system, and arterial oxygen and carbon dioxide t ensions were measured in 17 patients before and 0.5, 2, and 6 h after the administration of a single dose of either a synthetic surfactant ( SS), Exosurf (n = 10), or a bovine surfactant (BS), Survanta (n = 7). By 2 h, treatment with either BS or SS was followed by an increase in the arterial/alveolar ratio Of PO2 (a/A) and in FRC (p < 0.01 for both a/A and FRC). The a/A and FRC improved sooner (p < 0.001) and to a gr eater extent (p < 0.01) after BS than after SS. Compliance of the resp iratory system and V(T) were decreased after either BS or SS at 0.5 h (p < 0.01) and remained decreased after SS at 2 h (p < 0.01). There wa s no significant change in V(A) or V(A) after either BS or SS. Because FRC and a/A increased without an accompanying increase in V(A), V(A), or compliance of the respiratory system, we believe that the immediat e increase in FRC in this study was caused by stabilization of gas exc hange units already being ventilated in addition to recruitment of new units. Nitrogen clearance index decreased and effective breath fracti on increased after treatment, indicating an improved efficiency in gas mixing also thought to result from stabilization and maintenance of p atency of distal airways by surfactant.