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

ABSTRACT Objective To determine the regional ventilation characteristics during non-invasive ventilation in stable preterm infants. The secondary aims were 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 gestation receiving either CPAP (n=32) or nHF(n=8) if <36 weeks corrected gestation, and extubated for at least 24 hours at time of study. Interventions Continuous electrical impedance tomography imaging of regional ventilation during 60-minutes 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 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 (SD) CoV RL 69.1 (14.9)%) and the gravity non-dependent lung; ideal-actual CoV 1.4 (4.5). The central third of the lung received the most tidal volume, followed by the non-dependent and dependent regions (p<0.0001 repeated measure ANOVA). Ventilation inhomogeneity was associated with worse SpO 2 /FiO 2 , (p=0.031, r 2 0.12; linear regression). In those infants that later developed bronchopulmonary dysplasia (n=25) SpO 2 /FiO 2 was worse and non-dependent ventilation inhomogeneity 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 gravity non-dependent lung, with ventilation inhomogeneity associated with worse oxygenation.