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 (SpO ) 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 (F O ) was reduced stepwise at 5-min intervals to achieve peripheral SpO between 86% and 95%. The lowest permissible F O and SpO were 0.14% and 86%. We recorded SpO , F O , and the respiratory signal (respiratory inductive plethysmography). We calculated respiratory rate (RR), tidal volume (V ), minute ventilation (V ), and respiratory drive (ratio between V and inspiratory time, V /T ). SpO variability was expressed as the interquartile range (IQR).

RESULTS

F O 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 F O , 37 (65%) infants reduced their V , and 20 (35%) increased minute ventilation; 20 infants (35%) developed periodic breathing associated with increased SpO IQR and lower SpO minima, and 16 (28%) exhibited an oscillatory pattern in V and SpO without end-expiratory pauses, regardless of BPD severity.

CONCLUSION

In very preterm infants, a mild hypoxic challenge reduced ventilation, increased SpO variability and periodic breathing regardless of BPD severity.