467 - Physiologic Measurement at Discharge versus Oxygen at 36 weeks as Indicators of Neonatal Pulmonary Morbidity in VLBW Infants

Poster Number: 467
Publication Number: 467.229

Dale R. Gerstmann, Timpanogos Regional Hospital, Orem, UT, United States

Background: Several terms have been used to classify neonatal pulmonary morbidity (NPM). Northway (1967) described classic bronchopulmonary dysplasia (BPD) with the clinical correlate being neonatal chronic lung disease (CLD), defined as O2 need at 28d. Shennan (1988) found that O2 dependency at 36wk PCA had a better positive predictive value (PPV) for childhood pulmonary morbidity (CPM) than O2 at 28d (63% vs 38%). Thus, O2 at 36wk has been the standard for defining CLD. Walsh (2004), Ballard (2016), and others championed including physiologic measurement in assessing CLD using an oxygen reduction test, but this has not become routine practice. The Neonatal Research Network (2019) proposed a new stratified classification for NPM or “clinical BPD” not based on O2 needs. The PPV for CPM was improved to 81% using only respiratory support at 36wk. Their proposal did not include physiologic testing.

Objective: To compare physiologic testing at discharge (DC) to the usual definition of CLD, O2 at 36wk, in VLBW infants at a single center admitted between Jan 2012 and Aug 2021.

Design/Methods: We queried our VON dataset for VLBW infants DC'd to home, noting O2 at 36wk and birth and DC EGA and weight (WT). Our physiologic test was to have infants undergo a room air challenge at least 48h before DC. If unable to maintain SpO2>89%, they were placed in an O2 hood with 10LPM flow. O2 in the gas flow was titrated to achieve infant SpO2 92-95% and the FiO2 recorded. The partial pressure of inspired oxygen (PiO2) was calculated from the FiO2 based on the station pressure (645 mmHg at 4774 ft altitude). If needed, nasal cannula microflow (MF=O2 at < 0.10 LPM) was provided at DC. We compared each infant's DC PiO2 and VON designation for CLD, and also birth and DC EGA and WT, and DC HCT, for infants who did or did not need MF. The local hospital IRB approved the study.

Results: Nf134 VLBW infants. Birth EGA and WT were 29.8±2.3wk and 1.20±0.25kg. 69.4% (93/134) had CLD by VON. 73.9% (99/134) did not need MF at DC. PiO2 was 148±8mmHg. PiO2 vs VON CLD is shown in Fig 1. DC MF was 0.03±0.02LPM. There was no difference in DC EGA or HCT based on MF need (38.9±1.8wk MF+ vs 38.8±1.7wk MF-), (32.4±3.2% MF+ vs 32.7±4.4% MF-). Birth EGA and WT differed significantly (28.7±2.6wk MF+ vs 30.1±2.1wk MF-, p < 0.001), (1.07±0.25kg MF+ vs 1.27±0.23kg MF-, p=0.002) by T-test. 3 infants required DC FiO2 < 23% (sea level equivalent). VON CLD assignment overestimated NPM using physiologic testing by a factor of 31.5 (93/3).Conclusion(s): In this single-center study, physiologic testing at DC appeared to be more representative of NPM than did O2 at 36wk.
PiO2 at Discharge for All VLBW InfantsPiO2 by physiologic testing at discharge is shown for each infant, ordered left to right. Black bars indicate the infant was assigned as having CLD (O2 at 36wk PCA). Corresponding FiO2 at sea level is shown for reference.