Background Expired carbon dioxide (ECO2) indicates degree of lung aeration immediately after birth. Favourable ventilation techniques may be associated with higher ECO2 and a faster increase. Clinical condition will however also affect measured values. The aim of this study was to explore the relative impact of ventilation factors and clinical factors on ECO2 during bag-mask ventilation of near-term newborns.
Methods Observational study performed in a Tanzanian rural hospital. Side-stream measures of ECO2, ventilation data, heart rate and clinical information were recorded in 434 bag-mask ventilated newborns with initial heart rate <120 beats per minute. We studied ECO2 by clinical factors (birth weight, Apgar scores and initial heart rate) and ventilation factors (expired tidal volume, ventilation frequency, mask leak and inflation pressure) in random intercept models and Cox regression for time to ECO2 >2%.
Results ECO2 rose non-linearly with increasing expired tidal volume up to >10 mL/kg, and sufficient tidal volume was critical for the time to reach ECO2 >2%. Ventilation frequency around 30/min was associated with the highest ECO2. Higher birth weight, Apgar scores and initial heart rate were weak, but significant predictors for higher ECO2. Ventilation factors explained 31% of the variation in ECO2 compared with 11% for clinical factors.
Conclusions Our findings indicate that higher tidal volumes than currently recommended and a low ventilation frequency around 30/min are associated with improved lung aeration during newborn resuscitation. Low ECO2 may be used to identify unfavourable ventilation technique. Clinical factors are also associated with persistently low ECO2 and must be accounted for in the interpretation.
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Correction notice This article has been corrected since it was published.
Contributors KH, KS, HLE and JE had full access to all the data in the study, and take responsibility for the integrity of the data and the accuracy of the data analysis. HK, KS, JE and CK designed the study protocol. JE, JL, SJ, HK, JE and MT practically implemented, supervised and carried out the study and the data collection on site. JE gave technical support, extracted and processed the data. RH, KS, RH and JE performed the statistical analyses. KH drafted the initial manuscript. All authors have reviewed and approved the final manuscript as submitted.
Funding The study was partly funded by the Global Health and Vaccines Research (GLOBVAC) programme at the Research Council of Norway (project no. 2280203), Laerdal Global Health and the Laerdal Foundation. KH received a PhD grant from Helse Sør-Øst, Norway. MT and JL received unrestricted PhD grants from the Laerdal Foundation. KS is supported by an unrestricted grant from Oak Foundation, Geneva.
Disclaimer The funding sources had no role in the design and conduct of the study, collection, management, analysis and interpretation of the data, preparation, review or approval of the manuscript, and the decision to submit the manuscript for publication.
Competing interests JE is an employee of Laerdal Medical. JL is married to an employee at Laerdal Global Health.
Patient consent for publication Not required.
Ethics approval Ethical approval was granted by the National Institute for Medical Research in Tanzania (Ref. NIMR/HQ/R.8a/Vol.IX/1434) and the Regional Committee for Medical and Health Research Ethics for Western Norway (Ref. 2013/110).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available on reasonable request.
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