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

Abstract

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_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.

Results: 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).

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.

Keywords: neonatology; technology.