LAUSR

Oxygenation instability is not quantified or documented despite being common and correlated with neonatal morbidities, retinopathy of prematurity, and adverse 18-month outcomes. We developed a five-type SpO2 histogram classification system based on the SpO2 difference within the 10–90th cumulative time percentile (A) and the time percentage with SpO2 ≤80% (B). In type 1, A is <5% and in type 5, A and B are ≥10%. We then studied consecutive 12-h SpO2 frequency histograms in all infants ≤34 weeks gestation receiving respiratory support on day 1, over 6 months. Six thousand and sixteen histograms were obtained in 73 infants, 28.9 ± 3.0 weeks gestation, and birth weight (BW) 1318.5 ± 495 g. All types were common and did not overlap. Type 3–5 (“unstable”) histograms were more common in oxygen or any intubated support. Time in SpO2 <85% and <80% progressively increased in types 3–5. Among histograms in oxygen, the mean (±SD) of SpO2 medians was 92.8 ± 1.9. Infants ≤28 weeks exhibited three phases of SpO2 instability (stable–unstable–stable). Those developing unstable histograms during the first week received longer ventilatory support (median [IQR], 101 [66] vs. 62 [28] days) and supplemental oxygen (62.5 [72] vs. 40.5 [40] days), and more were on ventilatory support at 40 weeks (7/15 vs. 0/10). Classified SpO2 histograms quantify and document SpO2 instability and identify early infants at risk of prolonged respiratory support, while median SpO2 does not.