Significant hypercapnia either in CO2-insufflated or air-insufflated colonoscopy under deep sedation

BackgroundPrevious reports showed that CO2-insufflated colonoscopy is safe and less discomfortable. However, hypercapnia remains a vital concernment if deep sedation is necessary for difficult colonoscopy with prolonged CO2 insufflation. This observational study is to measure bodily CO2 subjected to colonoscopy facilitated by CO2- and air- or air-insufflation in conscious-sedation, deep-sedation and awake patients.ObjectiveTo investigate if CO2-insufflated colonoscopy could increase the risk of hypercapnia in awake, conscious-sedation and deep-sedation patients.Methods104 patients in our health center undergoing sequential esophagogastroscopy and colonoscopy screening were included. At patients’ request, incremental intravenous sedatives were given in order that the air-insufflated esophagogastroscopy could be carried out without the molestation of gag and cough reflexes. The sedation levels were re-evaluated before proceeding colonoscopy and the patients were divided into conscious-sedation (respond purposefully to verbal commands) and deep-sedation groups and randomly allocated for air or CO2 insufflation. Transcutaneous capnography (TcCO2) was recorded every minute throughout the colonoscopy procedure.ResultsThe baseline TcCO2 in the air- (50.9 ± 5.7 mmHg) and CO2-insufflated (53.1 ± 6.5 mmHg) groups under deep sedation was significantly higher than the groups under conscious-sedation and the awake groups (p < 0.01). In both air- and CO2-insufflation groups there were also a statistically significant (p < 0.01) correlation in TcCO2 between the start, the peak and the end of colonoscopy. TcCO2 did not significantly change throughout the colonoscopy in awake and conscious-sedation groups, either with air or CO2 insufflation. With deep sedation, TcCO2 significantly increased and peaked around the time when the scope touching the cecum, and then returned to original state with suction and withdrawl of the colonoscope without significant interaction of CO2 insufflation and deep sedation.ConclusionThe TcCO2 during colonoscopy was correlated to the data before inserting colonoscope but significantly different within awake, conscious-sedation and deep-sedation groups. TcCO2 did not change significantly either with CO2 insufflation or air insufflations in awake and conscious-sedation groups. However, in deep-sedation groups with significantly higher baseline TcCO2, further increase of TcCO2 were significant without interaction with CO2 insufflation. We concluded that when patients need deep sedation for colonoscopic procedures facilitated by gas insufflation, hypercapnia is still considerably present, not only with CO2 insufflation but also with air insufflation colonoscopy.