The Reference Interval for the Attainment of Comparable Term Functional Levels of Pulmonary Oxygenation Capacity in Healthy Preterm Infants: A Single-Center Retrospective Study.

OBJECTIVE

We aimed to identify the reference interval (RI) of the postmenstrual age (PMA) at which lung oxygenation capacity is sufficiently stable in healthy preterm infants.

DESIGN AND SETTING

A single-center, retrospective study involving a cohort of infants born at gestational age (GA) < 34 weeks who were discharged without respiratory support and experienced no short-term adverse respiratory outcomes.

OUTCOME MEASURES

The PMA when oxygen supplementation was discontinued (Stop-O), and subsequent SpO stabilization at ≥ 96% with room air spontaneous breathing for three consecutive days (Stable-SpO).

RESULTS

Of the 243 eligible infants, 176 meeting the Stable-SpO criteria before discharge were analyzed. The upper limit of the RI (97.5th percentile) for Stop-O was 40.2 weeks PMA and that for Stable-SpO was 41.7. Limited to infants with GA < 30 weeks, the 97.5th percentile of Stop-O and Stable-SpO was 41.9 and 42.9 weeks PMA, respectively. When both indices plotted against GA were divided by K-means clustering, one distinct cluster straddled a wide range of GA with delayed achievement of Stop-O (39.6, median weeks PMA) or Stable-SpO (40.6). The SpO status when Stable-SpO criteria was fulfilled (mean SpO, 97.3%; time spent with SpO > 90%, 97.7%) was nearly comparable to that of healthy term infants shortly after birth.

CONCLUSIONS

The lung oxygenation capacity in most healthy preterm infants was near-term levels by 42 weeks PMA. Our data might be useful for determining the optimal timing for assessing respiratory function as well as the presence or absence of bronchopulmonary dysplasia in preterm infants.