Exosurf rescue surfactant improves high ventilation-perfusion mismatch in respiratory distress syndrome.

OBJECTIVE To assess ventilation/perfusion (VA/Q) mismatch of the high type, following rescue surfactant therapy for respiratory distress syndrome. HYPOTHESIS Surfactant therapy reduces such mismatch. DESIGN Randomized, double-blind, placebo-controlled study, assessing VA/Q with the arterial-alveolar difference of CO2 tension (P(a-A)CO2). This difference was determined with capnometry and arterial blood gases, using the equation: P(a-A)CO2 equals arterial CO2 minus alveolar CO2 partial pressure. SETTING A level III nursery. PATIENTS Ten intubated infants with respiratory distress syndrome. INTERVENTION Infants were randomized to each receive two doses of surfactant or two doses of air placebo. RESULTS P(a-A)CO2 improved after surfactant and worsened after placebo (P = 0.0021), comparing slopes of 12-hr regression lines. A similar pattern occurred with oxygenation. These changes in P(a-A)CO2 and in oxygenation were minimally correlated within the surfactant group. CONCLUSION Exosurf rescue surfactant reduced VA/Q mismatch of the high type, over several hours.