Rationale: The transition to air-breathing at birth is a seminal respiratory event common to all humans, but the intrathoracic processes remain poorly understood. Objectives: The objectives of this prospective, observational study were to describe the spatiotemporal gas flow, aeration and ventilation patterns within the lung in term neonates undergoing successful respiratory transition. Methods: Electrical impedance tomography was used to image intrathoracic volume patterns for every breath until six minutes from birth in neonates born by elective cesearean section and not needing resuscitation. Breaths were classified by video data, and measures of lung aeration, tidal flow conditions and intrathoracic volume distribution calculated for each inflation. Measurements and Main results: 1401 breaths from 17 neonates met all eligibility and data analysis criteria. Stable functional residual capacity was obtained by median (IQR) 43 (21, 77) breaths. Breathing patterns changed from predominantly crying (80.9% first minute) to tidal breathing (65.3% sixth minute). From birth tidal ventilation was not uniform with the lung, favouring the right and non-dependent regions; p<0•001 versus left and dependent (mixed effects model). Initial crying created a unique pattern with delayed mid-expiratory gas flow associated with intrathoracic volume redistribution (pendelluft flow) within the lung. This preserved functional residual, especially within the dorsal and right regions. Conclusions: The commencement of air-breathing at birth generates unique flow and volume states associated with marked spatiotemporal ventilation inhomogeneity not seen elsewhere in respiratory physiology. At birth neonates innately brake expiratory flow to defend functional residual capacity gains and redistribute gas to less aerated regions.

ObjectivesTo 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.DesignProspective observational study.SettingTwo tertiary neonatal intensive care units.PatientsForty 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.InterventionsContinuous electrical impedance tomography imaging of regional ventilation during 60 min of quiet breathing on clinician-determined non-invasive settings.Main outcome measuresGravity-dependent and right–left centre of ventilation (CoV), percentage of whole lung tidal volume (VT) 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.ResultsVentilation was greater in the right lung (mean 69.1 (SD 14.9)%) total VT and the gravity-non-dependent (ND) lung; ideal–actual CoV 1.4 (4.5)%. The central third of the lung received the most VT, 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).ConclusionsThere 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.

ObjectivesVolume-targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set tidal volume (VTset) is accurately delivered. This prospective observational study aimed to determine the relationship between VTset, expiratory VT (VTe) and endotracheal tube leak in a modern neonatal ­volume-targeted ventilator (VTV) and the resultant partial arterial pressure of carbon dioxide (PaCO2) relationship with and without VTV.DesignContinuous inflations were recorded for 24 hours in 100 infants, mean (SD) 34 (4) weeks gestation and 2483 (985) g birth weight, receiving synchronised mechanical ventilation (SLE5000, SLE, UK) with or without VTV and either the manufacturer’s V4 (n=50) or newer V5 (n=50) VTV algorithm. The VTset, VTe and leak were determined for each inflation (maximum 90 000/infant). If PaCO2 was sampled (maximum of 2 per infant), this was compared with the average VTe data from the preceding 15 min.ResultsA total of 7 497 137 inflations were analysed. With VTV enabled (77 infants), the VTset−VTe bias (95% CI) was 0.03 (−0.12 to 0.19) mL/kg, with a median of 80% of VTe being ±1.0 mL/kg of VTset. Endotracheal tube leak up to 30% influenced VTset−VTe bias with the V4 (r2=−0.64, p<0.0001; linear regression) but not V5 algorithm (r2=0.04, p=0.21). There was an inverse linear relationship between VTe and PaCO2 without VTV (r2=0.26, p=0.004), but not with VTV (r2=0.04, p=0.10), and less PaCO2 within 40–60 mm Hg, 53% versus 72%, relative risk (95% CI) 1.7 (1.0 to 2.9).ConclusionVTV was accurate and reliable even with moderate leak and PaCO2 more stable. VTV algorithm differences may exist in other devices.

Unintentional hypothermia is a common occurrence during surgery in the OT and MRI in neonates, indicating that evidence-based warming strategies to prevent hypothermia should be developed.