Monitoring of exhaled carbon monoxide and carbon dioxide during lung cancer operation.

Objective: Carbon monoxide (CO) is expelled mainly via the lungs, so that exhaled carbon monoxide (Ex-CO) concentration reflects endogenous production. Recent reports have shown that Ex-CO levels are increased in critically ill patients and after anaesthesia and surgery. However, there has been no investigation of the changes in Ex-CO level during a lung operation. We continuously monitored Ex-CO and exhaled carbon dioxide (Ex-CO2) concentrations during surgery for lung cancer.

Methods: Eighteen lung cancer patients who underwent elective lung cancer lobectomy were enrolled in this study. All patients were endotracheally intubated and ventilated under general anaesthesia. Ex-CO and Ex-CO2 concentrations were separately monitored and recorded continuously using two sets of Carbolyzer® breath analysers (Taiyo Inc., Osaka, Japan).

Results: Ex-CO concentration increased rapidly in response to changes in body position from supine to decubitus and was significantly decreased when patients were once again lying back (supine 2). Upon restarting bilateral ventilation, Ex-CO concentration in the operated lung was significantly higher than that in the breathing lung. In the lateral decubitus position, Ex-CO2 concentration showed the same pattern of increase as seen for Ex-CO. In the operated lung, the Ex-CO2 concentrations changed significantly at clamping, declamping and supine 2. In the re-ventilated, operated lung, the Ex-CO2 concentration was significantly lower than in the breathing lung. In the breathing lung, the Ex-CO2 concentration did not exhibit any significant changes over the course of the operation.

Conclusions: When breathing was restarted, the Ex-CO level of the target lung was significantly higher than that of the breathing lung. The Ex-CO concentration was also affected by the surgical body position and this change was marked and transient.