Ventilatory response and stability of oxygen saturation during a hypoxic challenge in very preterm infants

Background Preterm infants have immature control of breathing and impaired pulmonary gas exchange. We hypothesized that infants with bronchopulmonary dysplasia (BPD) have a blunted ventilatory response and peripheral oxygen saturation (SpO2) instability during a hypoxic challenge. Methods We evaluated the response to hypoxia in 57 very preterm infants (38 no BPD, 10 mild BPD, 9 moderate‐to‐severe BPD) at 36 weeks' postmenstrual age. The fraction of inspired oxygen (FIO2) was reduced stepwise at 5‐min intervals to achieve peripheral SpO2 between 86% and 95%. The lowest permissible FIO2 and SpO2 were 0.14% and 86%. We recorded SpO2, FIO2, and the respiratory signal (respiratory inductive plethysmography). We calculated respiratory rate (RR), tidal volume (VT), minute ventilation (VE), and respiratory drive (ratio between VT and inspiratory time, VT/TI). SpO2 variability was expressed as the interquartile range (IQR). Results FIO2 was reduced from a median (Q1, Q3) of 0.21 (0.21, 0.21) to 0.17 (0.17, 0.18). We observed a marked individual variability in the ventilatory response to the hypoxic challenge, regardless of BPD severity. At the lowest permissible FIO2, 37 (65%) infants reduced their VE, and 20 (35%) increased minute ventilation; 20 infants (35%) developed periodic breathing associated with increased SpO2 IQR and lower SpO2 minima, and 16 (28%) exhibited an oscillatory pattern in VE and SpO2 without end‐expiratory pauses, regardless of BPD severity. Conclusion In very preterm infants, a mild hypoxic challenge reduced ventilation, increased SpO2 variability and periodic breathing regardless of BPD severity.