End tidal carbon dioxide levels during the resuscitation of prematurely born infants
Introduction
Immediately after birth, carbon dioxide elimination only occurs if there is effective ventilation of the lungs and associated vasodilation of the pulmonary vascular bed. In the absence of pulmonary vasodilation only 10% of the cardiac output is available to perfuse the lungs, greatly restricting the delivery of carbon dioxide (CO2) to the lungs. Thus, assessment of expired CO2 levels could be used to indicate that pulmonary vasodilation had occurred during resuscitation. Palme-Kilander et al. reported, in infants breathing spontaneously [1] and those who required intubation in the labour suite [2], that expired CO2 was rarely detected until the infants had made a spontaneous breath, suggesting that the infant's inspiration influenced pulmonary vascular bed vasodilation. In those studies [1], [2], however, expired gas was collected in 15 second aliquots and hence the temporal relationship between the first spontaneous breath and any change in the ETCO2 levels could not be investigated. We have now studied the temporal changes in ETCO2 levels and the infant's respiratory efforts during face mask resuscitation in the labour suite. Our aim was to determine if the infant's first respiratory effort was associated with a rise in the ETCO2 levels, suggesting that pulmonary vasodilation had occurred. A second aim was to determine whether the ETCO2 levels remained elevated with subsequent inflations not associated with inspiratory efforts, as such data would suggest that the increase in the pulmonary blood flow was maintained.
Section snippets
Methods
The study was conducted at King's College and Guy's and St Thomas' NHS Foundation Trusts between March 2010 and December 2010. Infants born before 34 weeks of gestation were eligible for entry into the study. Infants who made an inspiratory effort immediately after birth and before the start of resuscitation were excluded. Ethical approval was provided by the Outer North London Ethics Committee. The Committee required parental consent only for analysis and reporting of the data, this was
Results
During the study period, 177 infants of less than 34 weeks of gestation were born in the two units. Sixty-eight of those 177 prematurely born infants had respiratory function monitoring during the study period. Data from 28 infants were excluded as the infants had made at least one visible respiratory effort prior to the delivery of the first inflation.
Thus, 40 infants with a median gestational age of 30 weeks (range 23–34) and birth weight of 1226 g (range 545–2826) were included in the study.
Discussion
Our results suggest that pulmonary vasodilation was occurring with the infant's first inspiratory effort during face mask resuscitation, as inflations preceding the infant's respiratory efforts resulted in minimal ETCO2 levels, whereas, the median ETCO2 level associated with an active inflation was 3.4 kPa. Our findings are consistent with previous results [1], [2]. Palme-Kilander found that CO2 could only be identified in the 15 second aliquot of expired gas in which spontaneous inspirations had
Conflict of interest
None of the authors have a conflict of interest.
Funding
Dr Vadivelam Murthy is supported by the Guy's & St Thomas' Charity.
Role of funding source
The funding source provided Dr Murthy's salary and the monitoring equipment.
Acknowledgements
We thank Mrs Deirdre Gibbons for secretarial assistance.
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