Non-Intubated Capnography Is an Earlier Indicator of Hypoventilation Than Pulse Oximeter During Sedation for Colonoscopy

Abstract

Introduction: Hypoventilation during sedated colonoscopy examination is frequentry, indirectly monitored by arterial oxygen saturation levels (SpO2) monitoring (pulse oximeter), however, indication can be further delayed when supplemental oxygen is provided. Additional monitoring is needed in these cases. This study examines the advantages of non-intubated capnography monitoring during sedated colonoscopic procedures. Method: 44 adults were sedated during colonoscopy and Endotidal CO2(EtCO2) by non-intubated capnography (Oridion medical) and SpO2 by pulse oximeter were monitored. 19 received 2L/min supplemental oxygen (OS) and 25 breathed room air (RA). The relationship between SpO2 and EtCO2 was evaluated. All patients had ASA physical status 1-3 with no respiratory disease, and were sedated with flunitrazepam and meperidine. Results: 1. SpO2 and EtCO2 before sedation 96±1.9%, 34.5±3.4mmHg (RA) and 98±1.3%, 37.8±2.8%(OS). 2. During colonoscopy, hypoventilation occurred in both groups. The lowest SpO2 91±2.7% (RA), 97±2.2% (OS), while EtCO2 was 38.5±5mmHg (RA), 40.7±4.3mmHg (OS). 3. Peak EtCO2 during exam. 40.9±4.3mmHg (RA), 46±4.8mmHg (OS). SpO2 was 93±2.7% (RA), 99±1.3%. During peak hypoventilation, the RA group had >3% decrease in SpO2, while the OS group suffered no decrease in SpO2 during hypoventilation. Conclusion: Although the provision of supplemental oxygen can mask hypoventilation with SpO2 monitoring, capnography monitoring immediately identifies hypoventilation events. This study demonstrates the increased safety level when providing oxygen therapy to prevent dangerous hypoxemic episodes, while monitoring for hypoventilation using capnography.