The Collaborative Home Infant Monitoring Evaluation (CHIME) developed a research monitor (NIMS, Inc., Miami, FL) that, for the first three minutes of each hour monitored, automatically records: pulse oximetry, respiratory inductance plethysmography, ECG, heart rate trend, and sleep position. To elucidate normal patterns of hemoglobin oxygen saturation over time, we assessed 30,000 three minute epochs recorded overnight at home from 36 healthy term infants during the first 6 months of life. Sleep position was prone in 26%, supine in 47% and other in 27% of epochs. Baseline saturation was analyzed for each epoch during ≥10 s. of quiet breathing. Median baseline saturation was 97.9% (10th and 90th%iles, 95.2% and 99.7%): the median value was unchanged over time, but there was a progressive decrease in variability. There was no difference in baseline saturation by position. The baseline saturation was <90% in at least one epoch in 67% of infants and 22% of infants were <90% in 1-2% of their epochs. Each epoch was then assessed for episodes of an acute decline in saturation to <90% for ≥5 seconds to a lowest saturation ≥10% below baseline. These episodes were observed in 1% of all epochs recorded, 77% of which were associated with periodic breathing. At least one episode was seen in 72% of infants and 22% had an episode in 1-2% of their epochs. When epochs were stratified by position, these episodes were noted in only 0.19% of prone epochs vs. 1.17% of epochs in the supine position(OR 6.1, 95%CI 3.8, 9.8, p<0.001). In summary, healthy term infants generally have baseline saturation levels in the >95% range. Occasional periods of baseline saturation <90% and acute drops in saturation of≥10%, however, are not uncommon. Although baseline saturation was not influenced by sleep position, acute drops in saturation were more common in the supine position. These data are the first longitudinal, non-event oximetry data obtained at home for healthy term infants. They provide new insight into normal variability in saturation, and provide an essential frame of reference for interpreting diagnostic recordings. (NICHD ND 29067 29071 28971 29073 29060 29056 34625)

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