Predictive capability of End Tidal carbon dioxide and its correlation with arterial carbon dioxide in mechanically ventilated children

Abstract

Back ground:End-tidal carbon dioxide (ETCO2) is a surrogate, non-invasive measurement of arterial carbon dioxide (PaCO2); however, its clinical applicability in the intensive care unit setting remains unclear in pediatric population. Objectives:This study aims at assessing the effect of severity of lung disease and correlation between ETCO2 and PaCO2 Materials and methods: This was a prospective, nonrandomised study carried in pediatric intensive care unit of a tertiary care unit on 104 children requiring mechanical ventilation. Simultaneous ETCO2 and PaCO2 recording were taken, data on ventilator parameters recorded. Severity of lung disease was estimated by alveolar- arteriolar oxygen gradient, ventilation index and PaO2/FiO2 ratio. The PaCO2 and ETCO2 difference and its variability were studied. Results:208 samples were analysed where the mean PaCO2 value 28.9±9.7 mmhg was higher than mean ETCO2 value of 27.8±9.6 mmHg. The mean difference between PACO2 and ETCO2 was 1.6±3.23 mmHg. There was significant level of correlation between PACO2 and ETCO2 ( r=0.941, r2 = 0.886 , 95% CI= 0.95-0.97) for mild to moderate lung disease than severe lung disease. Systemic diseases, Ventilator index and alveolar arterial oxygen gradient did not have any significant correlation with the PACO2 and ETCO2 difference in our study. Conclusion: Significant correlation was found between the PaCO2 and ETCO2 value irrespective of the disease conditionand ETCO2 can be validated to predict PACO2.