Hypoxemia Episodes during Day and Night and Their Impact on Oxygen Saturation Targeting in Mechanically Ventilated Preterm Infants.

BACKGROUND: Hypoxemia episodes (HE) occur frequently in ventilated preterm infants and hinder the achievement of arterial oxygen saturation (SpO2) targets. These episodes may increase the risk for retinopathy of prematurity and neurodevelopmental disability. There are no data on the variation in HE and SpO2 targeting between day and night.

OBJECTIVE: The aim of this study was to evaluate the difference between day and night on the frequency and severity of HE and achievement of SpO2 targets.

METHODS: Twenty-four mechanically ventilated preterm infants with ≥4 episodes of SpO2 <75% over an 8-h period were enrolled. The fraction of inspired oxygen (FiO2), SpO2, and ventilator parameters were recorded over 24 h. Data from the day (9 a.m. to 5 p.m.) were compared to the night (9 p.m. to 5 a.m.) for the frequency of HE and proportion of time within and outside the target SpO2 range (90-95%).

RESULTS: The frequency of severe HE (SpO2 <75, ≥20 s) and prolonged severe HE (SpO2 <75, ≥60 s) was lower during the night compared to the day (1.6 ± 1.0 vs. 2.4 ± 1.3 episodes/h, p = 0.008, and 0.53 ± 0.35 vs. 0.90 ± 0.54 episodes/h, p = 0.018). There was no difference in mean episode duration. The frequency and duration of mild HE (SpO2 <85, ≥20 s) were lower during the night compared to the day (5.9 ± 2.7 vs. 7.1 ± 2.5 episodes/h, p = 0.003, and 72 ± 15 vs. 87 ± 25 s, p = 0.01, respectively). The proportion of time in severe hypoxemia (SpO2 <75%) was smaller, whereas time in hyperoxemia (SpO2 >95%) was greater, during the night compared to the day. The mean FiO2 did not differ between day and night.

CONCLUSION: In this group of infants with frequent HE, nighttime was associated with fewer episodes when compared to daytime. This is likely due to less handling and sensory stimulation during the night. The increase in time spent with hyperoxemia during the night is likely to be due to more tolerance of high SpO2 with less proactive weaning of FiO2.