Regional ventilation characteristics during non-invasive respiratory support in preterm infants

To determine the regional ventilation characteristics during non-invasive ventilation (NIV) in stable preterm infants. The secondary aim was to explore the relationship between indicators of ventilation homogeneity and other clinical measures of respiratory status.

Prospective observational study.

Two tertiary neonatal intensive care units.

Forty stable preterm infants born <30 weeks of gestation receiving either continuous positive airway pressure (n=32) or high-flow nasal cannulae (n=8) at least 24 hours after extubation at time of study.

Continuous electrical impedance tomography imaging of regional ventilation during 60 min of quiet breathing on clinician-determined non-invasive settings.

Gravity-dependent and right-left centre of ventilation (CoV), percentage of whole lung tidal volume (V_T) by lung region and percentage of lung unventilated were determined for 120 artefact-free breaths/infant (4770 breaths included). Oxygen saturation, heart and respiratory rates were also measured.

Ventilation was greater in the right lung (mean 69.1 (SD 14.9)%) total V_T and the gravity-non-dependent (ND) lung; ideal-actual CoV 1.4 (4.5)%. The central third of the lung received the most V_T, followed by the non-dependent and dependent regions (p<0.0001 repeated-measure analysis of variance). Ventilation inhomogeneity was associated with worse peripheral capillary oxygen saturation (SpO₂)/fraction of inspired oxygen (FiO₂) (p=0.031, r² 0.12; linear regression). In those infants that later developed bronchopulmonary dysplasia (n=25), SpO₂/FiO₂ was worse and non-dependent ventilation inhomogeneity was greater than in those that did not (both p<0.05, t-test Welch correction).

There is high breath-by-breath variability in regional ventilation patterns during NIV in preterm infants. Ventilation favoured the ND lung, with ventilation inhomogeneity associated with worse oxygenation.