Unravelling the complexities of the first breaths of life
Bibliographic record
Abstract
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. Funding National Health and Medical Research Council (Australia). Research in context Evidence before this study Birth requires the rapid transition from a fluid-filled to aerated lung. Despite being a seminal event for all humans, very little is understood about the physiological processes supporting the transition to air-breathing. Radiological and interventional studies from more than 40 years ago suggest that respiratory success at birth requires high intrathoracic pressure and flow states. Imaging studies in animals indicate that braking expiratory flow aids generating functional residual capacity. Added value of this study In term neonates during successful respiratory transition, breath-by-breath imaging of the intrathoracic gas flow and volume patterns within the lungs was possible with electrical impedance tomography. We found that aeration and ventilation were not uniform, with highly inhomogeneous, spatiotemporal volume patterns during attainment of functional residual capacity. Crying at birth created a unique expiratory pattern that allowed intrathoracic volume redistribution (pendelluft flow) within the lung, and preserved functional residual capacity. We hypothesise that newborns defend aeration from intrathoracic lung-fluid shifts by innately braking flow using the glottis and diaphragm. Implications of all the available evidence Real-time imaging of intrathoracic volume patterns in humans is practical and may offer measures that identify neonates needing resuscitation. Whilst inspiration generated aeration, expiration is equally important to the respiratory transition. Expiratory braking is essential as a mechanism of defending aeration; suggesting that positive end-expiratory pressure is likely to be the most important method of supporting the failing human lung at birth.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".