Continuous End-Tidal Carbon Dioxide Monitoring during Resuscitation of Asphyxiated Term Lambs

Abstract

Background: The Neonatal Resuscitation Program (NRP) recommends close monitoring of oxygenation during the resuscitation of newborns using a pulse oximeter. However, there are no guidelines for monitoring carbon dioxide (CO₂) to assess ventilation. Considering that cerebral blood flow (CBF) correlates directly with PaCO₂, continuous capnography monitoring of end-tidal CO₂ (ETCO₂) may limit fluctuations in PaCO₂ and, therefore, CBF during resuscitation of asphyxiated infants. Objective: To evaluate whether continuous monitoring of ETCO₂ with capnography during resuscitation of asphyxiated term lambs with meconium aspiration will prevent fluctuations in PaCO₂ and carotid arterial blood flow (CABF). Methods: Fifty-four asphyxiated term lambs with meconium aspiration syndrome were mechanically ventilated from birth to 60 min of age. Ventilatory parameters were adjusted based on clinical observation (chest excursion) and frequent arterial blood gas analysis in 24 lambs (control group) and 30 lambs (capnography group) received additional continuous ETCO₂ monitoring. Left CABF was monitored. We aimed to maintain PaCO₂ between 35 and 50 mm Hg and ETCO₂ between 30 and 45 mm Hg. Results: There was a significant correlation between ETCO₂ and PaCO₂ (R = 0.7, p < 0.001), between PaCO₂ and carotid flow (R = 0.52, p < 0.001) and between ETCO₂ and carotid flow (R = 0.5, p < 0.001). PaCO₂ and CABF during the first 60 min of age showed significantly higher fluctuation in the control group compared to the capnography group. Conclusion: Continuous monitoring of ETCO₂ using capnography with mechanical ventilation during and after resuscitation in asphyxiated term lambs with meconium aspiration limits fluctuations in PaCO₂ and CABF and may potentially limit brain injury.