The purpose of this study was to investigate the effectiveness of micro stream capnography in early recognition of adverse events during sedation for colonoscopy. Methods: This prospective randomized study was performed implemented on 82 adults scheduled for elective colonoscopy. SpO 2 , ETCO 2 and integrated pulmonary index (IPI) values were measured with the use of micro stream capnography and recorded. Arterial blood gas samples were taken at the beginning, 10 th minute and end of the procedure and analyzed. Results: The correlation between mean values of IPI and mean values of ETCO 2 , SpO 2 and PaCO 2 was not statistically significant. There was a statistically significant correlation between IPI value at the beginning and PaCO 2 value at the end of the procedure. Correlation of IPI value at the 10th minute with SpO 2 at the 10 th minute and SPO 2 value at the end of the procedure was statistically significant. Conclusion: Non-invasive ETCO 2 monitoring with micro stream capnography is correlated with PaCO 2 values in arterial blood gas analysis, which is useful for monitoring of sedation and hypoventilation during colonoscopy procedures. However, IPI monitoring is not of clinical benefit to early recognition of hypoventilation. Non-invasive ETCO 2 monitoring with micro stream capnography should be a part of routine monitoring for safe anesthetic practice outside the operating room.