Capnography and Patient Safety for Endoscopy Patrick D. Gerstenberger  Clinical Gastroenterology and Hepatology  Volume 8, Issue 5, Pages 423-425 (May 2010) DOI: 10.1016/j.cgh.2010.02.024 Copyright © 2010 AGA Institute Terms and Conditions

Figure 1 The initial waveform in this diagram is normal, showing a rapid rise from a baseline CO2 level of zero, as a mix of respiratory dead space and alveolar air is expired. The initial rise is followed by an alveolar plateau, representing alveolar CO2 levels. The final and maximal point of the alveolar plateau is the ETCO2 level, which is usually in the range of 35–45 mm Hg. The onset of inspiration immediately follows the ETCO2, with the CO2 level rapidly returning to baseline. During normal ventilation this waveform is repeated with each breath. The figure shows a transition from a normal waveform to abnormal waveforms with loss of the alveolar plateau that characterizes disordered breathing, which may be a sign of partial airway obstruction. Used with permission from Oridion Medical 1987 Ltd. Clinical Gastroenterology and Hepatology 2010 8, 423-425DOI: (10.1016/j.cgh.2010.02.024) Copyright © 2010 AGA Institute Terms and Conditions