Unravelling the complexities of the first breaths of life
Notice bibliographique
Résumé
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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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,006 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,001 |
| Communication savante | 0,002 | 0,002 |
| Science ouverte | 0,001 | 0,001 |
| Intégrité de la recherche | 0,001 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».