Background: Children are prone for pulmonary complications after cardiac surgery hence it is important to closely monitor those on mechanical ventilator. This study aims to determine correlation of end-tidal carbon dioxide by capnography and arterial carbon dioxide by arterial blood gas among mechanically ventilated patients after cardiac surgery.
Methods: Prospective cross-sectional study of patients with acyanotic and cyanotic congenital heart disease who underwent cardiac surgery. Data collected included demographic details and simultaneous EtCO2 (microstream capnography) and arterial blood gas values. We determined the correlation coefficient and degree of bias with 95% confidence interval between EtCO2 and PaCO2.
Results: There were 158 end-tidal and arterial CO2 pairs from 36 patients (18 with acyanotic and 18 with cyanotic congenital heart disease). The overall EtCO2 was significantly lower than the corresponding PaCO2 values. For the acyanotic heart disease, EtCO2 = 38 ± 4.2 mmHg vs PaCO2 39.5 ± 5.5 (P<0.001) with mean dfference of 1.5 + 3.5 (95% C.I. 0.63 - 2.4). For the cyanotic heart disease,EtCO2 = 37.9 ± 5.8 mmHg vs PaCO2 39.2 ± 6.2 (P<0.001) with mean difference of 1.4 ± 2.8 (95% C.I. 0.8-1.9). Scatter gram plot in acyanotic heart disease has a correlation coefficient of 0.774 (P<0.001) and in cyanotic heart disease has a correlation coefficient of 0.896 (P<0.001).
Conclusion: This study showed a good correlation of EtCO2 with PaCO2 in both acyanotic ad cyanotic congenital heart disease after cardiac surgery.
Keywords: end-tidal carbon dioxide, capnograhy, congenital heart disease