Variations in oxygen saturation of arterial blood in infants and children with congenital heart disease

Abstract

The oxygen saturation of systemic arterial blood was recorded by means of an oximeter for periods of 30 seconds or more in 43 infants or children who had severe cyanotic congenital heart disease (arterial oxygen saturation less than 75%). The magnitude and phase of variability were recorded and were corrected for instrumental distortion for periods of three seconds or more. Nonrandom variations of significant magnitude occurred at respiratory frequency in 19 patients, of whom 16 had obstruction to pulmonary inflow, indicating great variation in the magnitude of the right to left shunt during the respiratory cycle. In other conditions, such as transposition of the great arteries without pulmonary stenosis, the absence of systematic variations suggests that intracardiac and great vessel shunting occurs primarily at cardiac frequency.