Elsevier

Early Human Development

Volume 88, Issue 10, October 2012, Pages 783-787
Early Human Development

End tidal carbon dioxide levels during the resuscitation of prematurely born infants

https://doi.org/10.1016/j.earlhumdev.2012.05.003Get rights and content

Abstract

Background

Successful resuscitation of prematurely born infants is dependent on achieving adequate alveolar ventilation and vasodilation of the pulmonary vascular bed. Elevation of end-tidal carbon dioxide (ETCO2) levels may indicate pulmonary vasodilation.

Aims

This research aims to study the temporal changes in ETCO2 levels and the infant's respiratory efforts during face mask resuscitation in the labour suite, and to determine if the infant's first inspiratory effort was associated with a rise in the ETCO2 levels, suggesting pulmonary vasodilation had occurred.

Study design

This study is an observational one.

Subjects

The subjects of the study are forty infants with a median gestational age of 30 weeks (range 23–34).

Outcome measures

Inflation pressures, expiratory tidal volumes and ETCO2 levels were measured.

Results

The median expiratory tidal volume of inflations prior to the onset of the infant's respiratory efforts (passive inflations) was lower than that of the inflation associated with the first inspiratory effort (active inflation) (1.8 (range 0.1–7.3) versus 6.3 ml/kg (range 1.9–18.4), p < 0.001), as were the median ETCO2 levels (0.3 (range 0.1–2.1) versus 3.4 kPa (0.4–11.5), p < 0.001). The median expiratory tidal volume (4.5 ml/kg (range 0.5–18.3)) and ETCO2 level (2.2 kPa (range 0.3–9.3)) of the two passive inflations following the first active inflation were also higher than the median expiratory tidal volume and ETCO2 levels of the previous passive inflations (p < 0.001, p < 0.0001 respectively).

Conclusion

These results suggest that during face mask resuscitation, improved carbon dioxide elimination, likely due to pulmonary vasodilation, occurred with the onset of the infant's respiratory efforts.

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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