Unravelling the complexities of the first breaths of life

Abstract

Background: The transition to air-breathing at birth is a seminal, but poorly understood, respiratory event common to all humans. The objectives of this prospective, observational study were to describe the spatiotemporal gas flow, aeration and ventilation patterns occurring within the lung in neonates during successful respiratory transition. Methods: Electrical impedance tomography was used to image intrathoracic volume patterns for every breath until six minutes from birth in term infants 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. Findings: 1401 breaths (n=17 neonates) met 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). Tidal ventilation was inhomogeneous at birth, favouring the right and non-dependent lung; p<0.001 versus left and dependent lung (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 capacity (70.8% cries), especially within the dorsal and right lung. Interpretation: 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.

Extubation generates lung volume inhomogeneity in preterm infants

“…In addition, during ETT CPAP the glottis is bypassed, removing the important role it plays in maintaining intra-thoracic volume during expiration (intrinsic PEEP). 17 Interestingly, EELV remained below pre-extubation values after 20 min of nCPAP, presumably due to the innate differences in transmissible pressures between invasive and non-invasive support. Measurements beyond 20 minutes would be useful to determine whether nCPAP eventually regains global EELV.…”

Extubation generates lung volume inhomogeneity in preterm infants

“…In addition, during ETT CPAP the glottis is bypassed, removing the important role it plays in maintaining intra-thoracic volume during expiration (intrinsic PEEP). 17 Interestingly, EELV remained below pre-extubation values after 20 min of nCPAP, presumably due to the innate differences in transmissible pressures between invasive and non-invasive support.…”