Abstract
As neonatal resuscitation critically depends upon lung aeration at birth, knowledge of the progression of this process is required to guide ongoing care. We investigated whether expired CO2 (ECO2) levels indicate the degree of lung aeration immediately after birth in two animal models and in preterm infants. Lambs were delivered by caesarean section and ventilated from birth. In lambs, ECO2 levels were significantly (p<0.0001) related to tidal volumes and CO2 clearance/breath increased exponentially when tidal volumes were greater than 6 mL/kg. Preterm (28 days of gestation; term = 32 days) rabbits were also delivered by caesarean section and lung aeration was measured using phase contrast X-ray imaging. In rabbit kittens, ECO2 levels were closely related (p<0.001) to lung volumes at end-inflation and were first detected when ∼7% of the distal lung regions were aerated. ECO2 levels in preterm infants at birth also correlated with tidal volumes. In each infant, ECO2 levels increased to >10 mmHg 28 (median) (21-36) seconds before the heart rate increased above 100 beats per minute. These data demonstrate that ECO2 levels can indicate the relative degree of lung aeration after birth and can be used to clinically assess ventilation in the immediate newborn period.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Animals, Newborn
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Carbon Dioxide / blood
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Carbon Dioxide / metabolism*
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Exhalation*
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Female
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Lung / physiology*
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Pregnancy
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Premature Birth
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Rabbits
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Respiratory Function Tests
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Sheep
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Tidal Volume
Grants and funding
This research is supported by Australian Research Council (ARC), Australian National Health and Medical Research Council (NHMRC #491103) and the Victorian Government’s Operational Infrastructure Support Program. Authors acknowledge travel funding provided by the International Synchrotron Access Program (ISAP) managed by the Australian Synchrotron and funded by the Australian Government. The authors also gratefully acknowledge support provided by the SPring-8 synchrotron facility (Japan), granted by the SPring-8 Program Review Committee (proposal nos. 2010B0022). GMS acknowledges funds by the Laerdal Foundation for Acute Medicine. MLS was a recipient of an Australian NHMRC Postgraduate Scholarship, MJK was a recipient of an ARC Australian Research Fellowship and PGD and SBH are recipients of Australia NHMRC Research Fellowships. ABtP was a recipient of a Veni-grant, The Netherlands Organisation for Health Research and Development (ZonMw), part of the Innovational Research Incentives Scheme Veni-Vidi-Vici (project nos. 91612027). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.