Noninvasive Measurement of Carbon Dioxide during One-Lung Ventilation with Low Tidal Volume for Two Hours: End-Tidal versus Transcutaneous Techniques

BackgroundThere may be significant difference between measurement of end-tidal carbon dioxide partial pressure (PetCO₂) and arterial carbon dioxide partial pressure (PaCO₂) during one-lung ventilation with low tidal volume for thoracic surgeries. Transcutaneous carbon dioxide partial pressure (PtcCO₂) monitoring can be used continuously to evaluate PaCO₂ in a noninvasive fashion. In this study, we compared the accuracy between PetCO₂ and PtcCO₂ in predicting PaCO₂ during prolonged one-lung ventilation with low tidal volume for thoracic surgeries.MethodsEighteen adult patients who underwent thoracic surgeries with one-lung ventilation longer than two hours were included in this study. Their PetCO₂, PtcCO₂, and PaCO₂ values were collected at five time points before and during one-lung ventilation. Agreement among measures was evaluated by Bland-Altman analysis.ResultsNinety sample sets were obtained. The bias and precision when PtcCO₂ and PaCO₂ were compared were 4.1 ± 6.5 mmHg during two-lung ventilation and 2.9 ± 6.1 mmHg during one-lung ventilation. Those when PetCO₂ and PaCO₂ were compared were -11.8 ± 6.4 mmHg during two-lung ventilation and -11.8 ± 4.9 mmHg during one-lung ventilation. The differences between PtcCO₂ and PaCO₂ were significantly lower than those between PetCO₂ and PaCO₂ at all five time-points (p < 0.05).ConclusionsPtcCO₂ monitoring was more accurate for predicting PaCO₂ levels during prolonged one-lung ventilation with low tidal volume for patients undergoing thoracic surgeries.