Standardization and Validation of Non-invasive Monitoring of End Tidal Carbon Dioxide in Neonates via Nasal Cannula: An Observational Study

Abstract

<strong><em>Background:</em></strong> Carbon dioxide (CO₂) is a by-product of cellular metabolism, which could be considered as a reflection of metabolism, circulation, and ventilation. Arterial blood gas analysis (ABG) is the gold standard of monitoring for CO₂. However, is an expensive method leading to blood loss and iatrogenic anemia. In addition, each sample is only a snapshot view of the sampling moment. End-tidal CO₂ (ETCO₂) measurement gives a non-invasive and continuous monitoring of exhaled CO₂. Therefore, this study aimed to validate the non-invasive CO₂ measurement performed by nasal cannula and evaluate the correlation with partial pressure of arterial CO₂ (PaCO₂ ) in neonates.<br /> <strong><em>Methods:</em></strong> This single-center observational study was conducted in the Neonatal Intensive Care Unit (NICU), Kasturba Hospital, Manipal, India. PaCO₂ was reported on routine ABG within a 15-minute interval of ABG sampling. Moreover, partial pressure of end-tidal carbon dioxide (PetCO₂) was noted at continuous 30-sec intervals (i.e., 30, 60, 90, ..., 180) up to 3 minutes. The values of PaCO₂ and PetCO₂ were found to be correlated with Pearson correlation and were shown by scattered plot. Regression analysis was used to get the prediction equation and the variance.<br /> <strong><em>Results</em></strong><strong><em>:</em></strong> A total of 70 samples were taken in the initial phase to study the correlation between PaCO₂ and measured PetCO₂. Pearson correlation showed a moderate positive correlation (r= 0.589) between PetCO₂ and measured PaCO₂. Regression analysis demonstrated a variance of 33.8% between the measured PetCO₂ and PaCO₂, which was statistically significant (P<0.001). A prediction equation was obtained for PaCO₂. In the final phase, 20 samples were recruited to standardize and validate the prediction equation. The PaCO₂ was calculated using the predicted equation and a new prediction equation was obtained.<br /> <strong><em>Conclusion:</em></strong> According to the findings of this study, there is a good correlation (r=0.681) between the non-invasively measured PetCO₂ and PaCO₂.