Simplified Bedside Assessment Of Pulmonary Gas Exchange In Very Preterm Infants At 36 Weeks' Postmenstrual Age

Introduction We aimed to develop and validate a prediction table for a simplified measure of rightward shift of the fetal oxyhaemoglobin saturation (SpO(2)) versus inspired oxygen pressure (P O-I(2)) curve as an objective marker of lung disease severity in very preterm infants, independent of unit altitude or oxygen prescribing policies. Methods Very preterm infants (n=219) had an oxygen reduction test at median (IQR) test age of 35(4) (34(5)-36(0)) weeks' postmenstrual age (PMA). Shift was derived from at least three paired SpO(2) versus P O-I(2) measurements using a computer algorithm, using the fetal oxyhaemoglobin dissociation curve as the reference. Linear regression of resultant shift values enabled construction of a table to predict shift using a single paired SpO(2) versus P O-I(2) measurement, validated subsequently in a separate infant cohort using Bland-Altman analysis. Receiver operating curve analysis provided threshold values equating to a clinical diagnosis of mild bronchopulmonary dysplasia (BPD) or moderate to severe BPD. Results The median (IQR) age of 63 infants in the validation cohort was 36(0) (35(6)-36(2)) weeks' PMA. Mean difference (95% CI) between predicted and measured shift was 2.1 (-0.8% to 4.9%) with wide limits of agreement (-20.7% to 24.8%). Predicted shift >10.1 kPa identified mild BPD with 71% sensitivity and 88% specificity while values>13.0 kPa identified moderate to severe BPD with 81% sensitivity and 100% specificity. Discussion Shift predicted from a single paired SpO(2) versus P O-I(2) measurement using our validated table enables objective bedside screening of lung disease severity in very preterm infant cohorts at 36 weeks' PMA.