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

OBJECTIVES

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.

DESIGN

Prospective observational study.

SETTING

Two tertiary neonatal intensive care units.

PATIENTS

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.

INTERVENTIONS

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

MAIN OUTCOME MEASURES

Gravity-dependent and right-left centre of ventilation (CoV), percentage of whole lung tidal volume (V) 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.

RESULTS

Ventilation was greater in the right lung (mean 69.1 (SD 14.9)%) total V and the gravity-non-dependent (ND) lung; ideal-actual CoV 1.4 (4.5)%. The central third of the lung received the most V, 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 (SpO)/fraction of inspired oxygen (FiO) (p=0.031, r 0.12; linear regression). In those infants that later developed bronchopulmonary dysplasia (n=25), SpO/FiO was worse and non-dependent ventilation inhomogeneity was greater than in those that did not (both p<0.05, t-test Welch correction).

CONCLUSIONS

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.