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) versus inspired oxygen pressure (O) 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 (34-36) weeks' postmenstrual age (PMA). Shift was derived from at least three paired SpO versus O 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 versus O 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 (35-36) 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 versus O measurement using our validated table enables objective bedside screening of lung disease severity in very preterm infant cohorts at 36 weeks' PMA.