Simultaneous measurement of preductal and postductal oxygen saturation by pulse oximetry in hyaline membrane disease.

Preductal and postductal oxygen saturation were compared in 20 ventilated preterm infants with hyaline membrane disease to establish the frequency of right to left shunting and to assess the accuracy of postductus arteriosus blood gas sampling. One hundred and thirty eight comparisons were made and the frequency of right to left shunting was 17% (95% confidence interval 12 to 25%). Shunting episodes with possible preductal hyperoxia occurred far less commonly on a maximum of 5% of occasions. The findings in infants under 1000 g and of 24-28 weeks' gestation were not significantly different from larger or more mature infants. Shunting occurred significantly more frequently in very ill infants who subsequently died as a result of respiratory disease.