Does pulse oximetry accurately monitor a patient's ventilation during sedated endoscopy under oxygen supplementation?

INTRODUCTION Pulse oximetry (SpO2) measures oxygen saturation but not alveolar ventilation. Its failure to detect alveolar hypoventilation during sedated endoscopy under oxygen supplementation has been reported. The aim of this study was to measure the masking effect of oxygen supplementation in SpO2 when alveolar hypoventilation develops during sedated endoscopy. METHODS A total of 70 patients undergoing sedated diagnostic colonoscopy were randomly divided into two groups - oxygen supplementation group (n = 35) and room air breathing group (n = 35). SpO2 and end-tidal carbon dioxide (etCO2) were measured by non-intubated capnography during the procedure for all the patients. RESULTS The rise of etCO2 caused by alveolar hypoventilation was comparable in the two groups after sedation. SpO2 was significantly higher in the oxygen supplementation group than in the room air breathing group (98.6% ± 1.4% vs. 93.1% ± 2.9%; p < 0.001) at peak etCO2, and oxygen supplementation caused SpO2 to be overestimated by greater than 5% when compared with room air. SpO2 at peak etCO2 was reduced from the baseline before sedation for the oxygen supplementation and room air breathing groups by 0.5% ± 1.1% and 4.1% ± 3.1%, respectively (p < 0.001). CONCLUSION SpO2 alone is not adequate for monitoring alveolar ventilation during sedated endoscopy under oxygen supplementation due to possible delays in detecting alveolar hypoventilation in patients. Even if SpO2 decreases by only 1% during the procedure and its level remains near 100%, physicians should consider the onset of severe alveolar hypoventilation, which requires immediate intervention.

[1]  J. Charlton,et al.  Recommendations for standards of sedation and patient monitoring during gastrointestinal endoscopy. , 1991, Gut.

[2]  T. Clutton-Brock,et al.  The benefits and pitfalls of pulse oximetry. , 1993, BMJ.

[3]  M. Freeman,et al.  Carbon dioxide retention and oxygen desaturation during gastrointestinal endoscopy. , 1993, Gastroenterology.

[4]  H. Hosie,et al.  Limitations of pulse oximetry: respiratory insufficiency--a failure of detection. , 1993, BMJ.

[5]  M E Ryan,et al.  Complications of endoscopic biliary sphincterotomy. , 1996, The New England journal of medicine.

[6]  J. Miner,et al.  End-tidal carbon dioxide monitoring during procedural sedation. , 2002, Academic emergency medicine : official journal of the Society for Academic Emergency Medicine.

[7]  Gregory Zuccaro,et al.  Automated graphic assessment of respiratory activity is superior to pulse oximetry and visual assessment for the detection of early respiratory depression during therapeutic upper endoscopy. , 2002, Gastrointestinal endoscopy.

[8]  P. Stonebridge,et al.  Analysis of 153 deaths after upper gastrointestinal endoscopy: room for improvement? , 2003, Surgical Endoscopy And Other Interventional Techniques.

[9]  D. Faigel,et al.  Guidelines for conscious sedation and monitoring during gastrointestinal endoscopy. , 2003, Gastrointestinal endoscopy.

[10]  L. Koniaris,et al.  Capnographic monitoring of ventilatory status during moderate (conscious) sedation , 2003, Surgical Endoscopy And Other Interventional Techniques.

[11]  Robert A. Smith,et al.  Supplemental oxygen impairs detection of hypoventilation by pulse oximetry. , 2004, Chest.

[12]  F. Khandwala,et al.  Deep Sedation Occurs Frequently During Elective Endoscopy with Meperidine and Midazolam , 2004, The American Journal of Gastroenterology.

[13]  D. Goldmann,et al.  Microstream Capnography Improves Patient Monitoring During Moderate Sedation: A Randomized, Controlled Trial , 2006, Pediatrics.

[14]  Michelle A. Anderson,et al.  Sedation and anesthesia in GI endoscopy. , 2008, Gastrointestinal endoscopy.

[15]  T. Stevens,et al.  Capnographic monitoring of respiratory activity improves safety of sedation for endoscopic cholangiopancreatography and ultrasonography. , 2009, Gastroenterology.

[16]  C. Lien.  Capnography enhances surveillance of respiratory events during procedural sedation: a meta-analysis , 2012 .