Hostname: page-component-546b4f848f-gfk6d Total loading time: 0 Render date: 2023-05-31T00:02:08.668Z Has data issue: false Feature Flags: { "useRatesEcommerce": true } hasContentIssue false

A comparative evaluation of capnometry versus pulse oximetry during procedural sedation and analgesia on room air

Published online by Cambridge University Press:  21 May 2015

Marco L.A. Sivilotti*
Department of Emergency Medicine, Queen's University, Kingston, Ont. Department of Pharmacology & Toxicology, Queen's University, Kingston, Ont.
David W. Messenger
Department of Emergency Medicine, Queen's University, Kingston, Ont.
Janet van Vlymen
Department of Anesthesiology, Queen's University, Kingston, Ont.
Paul E. Dungey
Department of Emergency Medicine, Queen's University, Kingston, Ont.
Heather E. Murray
Department of Emergency Medicine, Queen's University, Kingston, Ont. Department of Community Health & Epidemiology, Queen's University, Kingston, Ont.
76 Stuart St., Department of Emergency Medicine, Queen's University, Kingston ON K7L 2V7;


HTML view is not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Important questions remain regarding how best to monitor patients during procedural sedation and analgesia (PSA). Capnometry can detect hypoventilation and apnea, yet it is rarely used in emergency patients. Even the routine practice of performing preoxygenation in low-risk patients is controversial, as supplementary oxygen can delay the detection of respiratory depression by pulse oximetry. The purpose of this study was to determine whether the capnometer or the pulse oximeter would first detect respiratory events in adults breathing room air.


During a randomized clinical trial comparing fentanyl with low-dose ketamine for PSA with titrated propofol, patients were monitored using pulse oximetry and continuous oral–nasal sampled capnography. Supplemental oxygen was administered only for oxygen desaturation. Sedating physicians identified prespecified respiratory events, including hypoventilation (end-tidal carbon dioxide > 50 mm Hg, rise of 10 mm Hg from baseline or loss of waveform) and oxygen desaturation (pulse oximetry < 92%). These events and their timing were corroborated by memory data retrieved from the monitors.


Of 63 patients enrolled, 57% (36) developed brief oxygen desaturation at some point during the sedation. All responded to oxygen, stimulation or interruption of propofol. Measurements of end-tidal carbon dioxide varied substantially between and within patients before study intervention. Hypoventilation (19 patients, 30%) was only weakly associated with oxygen desaturation (crude odds ratio 1.4 [95% confidence interval 0.47 to 4.3]), and preceded oxygen desaturation in none of the 12 patients in whom both events occurred (median lag 1:50 m:ss [interquartile range 0:01 to 3:24 m:ss]).


During PSA in adults breathing room air, desaturation detectable by pulse oximeter usually occurs before overt changes in capnometry are identified.

Original Research • Recherche originale
Copyright © Canadian Association of Emergency Physicians 2010



1.Messenger, DW, Sivilotti, MLA. Procedural sedation and analgesia. In: Rowe, BH, editor. Evidence-based emergency medicine. West Sussex (UK): Wiley-Blackwell; 2009. p. 553–60.Google Scholar
2.Deitch, K, Chudnofsky, CR, Dominici, P. The utility of supplemental oxygen during emergency department procedural sedation with propofol: a randomized, controlled trial. Ann Emerg Med 2008;52:18.CrossRefGoogle ScholarPubMed
3.Green, SM, Krauss, B. Supplemental oxygen during propofol sedation: Yes or no? Ann Emerg Med 2008;52:910.CrossRefGoogle ScholarPubMed
4.Keidan, I, Gravenstein, D, Berkenstadt, H, et al. Supplemental oxygen compromises the use of pulse oximetry for detection of apnea and hypoventilation during sedation in simulated pediatric patients. Pediatrics 2008;122:293–8.CrossRefGoogle ScholarPubMed
5.Deitch, K, Chudnofsky, CR, Dominici, P. The utility of supplemental oxygen during emergency department procedural sedation and analgesia with midazolam and fentanyl: a randomized, controlled trial. Ann Emerg Med 2007;49:18.CrossRefGoogle ScholarPubMed
6.Krauss, B, Hess, DR. Capnography for procedural sedation and analgesia in the emergency department. Ann Emerg Med 2007;50:172–81.CrossRefGoogle ScholarPubMed
7.Godwin, SA, Caro, DA, Wolf, SJ, et al. Clinical policy: procedural sedation and analgesia in the emergency department. Ann Emerg Med 2005;45:177–96.CrossRefGoogle ScholarPubMed
8.Walker, BH Jr., Green, SM, Krauss, B. Is capnography necessary for propofol sedation? Ann Emerg Med 2004;44:549–50.CrossRefGoogle ScholarPubMed
9.Miner, JR, Heegaard, W, Plummer, D. End-tidal carbon dioxide monitoring during procedural sedation. Acad Emerg Med 2002;9:275–80.CrossRefGoogle ScholarPubMed
10.Innes, G, Murphy, M, Nijssen-Jordan, C, et al. Procedural sedation and analgesia in the emergency department Canadian consensus guidelines. J Emerg Med 1999;17:145–56.CrossRefGoogle ScholarPubMed
11.Canadian Anesthesiologists’ Society. Guidelines to the practice of anesthesia. Can J Anesth 2010;57(suppl 1):5887.Google Scholar
12.Wright, SW. Conscious sedation in the emergency department: the value of capnography and pulse oximetry. Ann Emerg Med 1992;21:551–5.CrossRefGoogle ScholarPubMed
13.Miner, JR, Biros, M, Krieg, S, et al. Randomized clinical trial of propofol versus methohexital for procedural sedation during fracture and dislocation reduction in the emergency department. Acad Emerg Med 2003;10:931–7.CrossRefGoogle ScholarPubMed
14.Miner, JR, Biros, MH, Heegaard, W, et al. Bispectral electroencephalographic analysis of patients undergoing procedural sedation in the emergency department. Acad Emerg Med 2003;10:638–43.CrossRefGoogle ScholarPubMed
15.Burton, JH, Harrah, JD, Germann, CA, et al. Does end-tidal carbon dioxide monitoring detect respiratory events prior to current sedation monitoring practices? Acad Emerg Med 2006;13:500–4.CrossRefGoogle ScholarPubMed
16.Hart, LS, Berns, SD, Houck, CS, et al. The value of end-tidal CO2 monitoring when comparing three methods of conscious sedation for children undergoing painful procedures in the emergency department. Pediatr Emerg Care 1997;13:189–93.CrossRefGoogle ScholarPubMed
17.Tobias, JD. End-tidal carbon dioxide monitoring during sedation with a combination of midazolam and ketamine for children undergoing painful, invasive procedures. Pediatr Emerg Care 1999;15:173–5.CrossRefGoogle ScholarPubMed
18.Yldzdas, D, Yapcoglu, H, Ylmaz, HL. The value of capnography during sedation or sedation/analgesia in pediatric minor procedures. Pediatr Emerg Care 2004;20:162–5.CrossRefGoogle ScholarPubMed
19.Anderson, JL, Junkins, E, Pribble, C, et al. Capnography and depth of sedation during propofol sedation in children. Ann Emerg Med 2007;49:913.CrossRefGoogle ScholarPubMed
20.Wang, VJ, Krauss, B. Carbon dioxide monitoring in emergency medicine training programs. Pediatr Emerg Care 2002;18:251–3.CrossRefGoogle ScholarPubMed
21.Messenger, DW, Murray, HE, Dungey, PE, et al. Subdissociative-dose ketamine versus fentanyl for analgesia during propofol procedural sedation: a randomized clinical trial. AcadEmerg Med 2008;15:877–86.Google ScholarPubMed
22.Chernik, DA, Gillings, D, Laine, H, et al. Validity and reliability of the Observer’s Assessment of Alertness/Sedation Scale: study with intravenous midazolam. J Clin Psychopharmacol 1990;10:244–51.Google ScholarPubMed
23.McQuillen, KK, Steele, DW. Capnography during sedation/ analgesia in the pediatric emergency department. Pediatr Emerg Care 2000;16:401–4.CrossRefGoogle ScholarPubMed
24.Vargo, JJ, Zuccaro, G Jr, Dumot, JA, 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. Gastrointest Endosc 2002;55:826–31.CrossRefGoogle ScholarPubMed
25.McNulty, SE, Roy, J, Torjman, M, et al. Relationship between arterial carbon dioxide and end-tidal carbon dioxide when a nasal sampling port is used. J Clin Monit 1990;6:93–8.CrossRefGoogle Scholar
26.Cload, B, Howes, DW, Sivilotti, ML, et al. Where is the ET tube? CJEM 2006;8:436, 446–7.CrossRefGoogle ScholarPubMed
27.Ward, KR, Yealy, DM. End-tidal carbon dioxide monitoring in emergency medicine. Part 2: clinical applications. Acad Emerg Med 1998;5:637–46.CrossRefGoogle ScholarPubMed
28.Ward, KR, Yealy, DM. End-tidal carbon dioxide monitoring in emergency medicine. Part 1: basic principles. Acad Emerg Med 1998;5:628–36.CrossRefGoogle ScholarPubMed
29.Murphy, MF, Krauss, B. Pulse oximetry and capnography/ capnometry. In: Walls, RM, editor. Manual of emergency airway management. Philadelphia (PA): Lippincott Williams & Wilkins; 2008. p. 429–38.Google Scholar
30.Green, SM, Pershad, J. Should capnographic monitoring be standard practice during emergency department procedural sedation and analgesia? Pro and con. Ann Emerg Med 2010;55:265–7.CrossRefGoogle ScholarPubMed
31.Bhatt, M, Kennedy, RM, Osmond, MH, et al. Consensus-based recommendations for standardizing terminology and reporting adverse events for emergency department procedural sedation and analgesia in children. Ann Emerg Med 2009;53:426–35.CrossRefGoogle ScholarPubMed
32.Green, SM, Yealy, DM. Procedural sedation goes Utstein: the Quebec guidelines. Ann Emerg Med 2009;53:436–8.CrossRefGoogle ScholarPubMed
33.American Society of Anesthesiologists Task Force on Sedation and Analgesia by Non-anesthesiologists. Practice guidelines for sedation and analgesia by non-anesthesiologists: an updated report by the American Society of Anesthesiologists task force on sedation and analgesia by non-anesthesiologists. Anesthesiology 2002;96:1004–17.CrossRefGoogle Scholar
34.Deitch, K, Miner, JR, Chudnofsky, CR, et al. Does end-tidal CO2 monitoring during emergency department procedural sedation and analgesia with propofol decrease the incidence of hypoxic events? A randomized, controlled trial. Ann Emerg Med 2010;55:258–64.CrossRefGoogle ScholarPubMed
35.Lightdale, JR, Goldmann, DA, Feldman, HA, et al. Microstream capnography improves patient monitoring during moderate sedation: a randomized, controlled trial. Pediatrics 2006;117:e1170–8.CrossRefGoogle ScholarPubMed
36.Stemp, LI, Ramsay, MA. Pulse oximetry in the detection of hypercapnia. Am J Emerg Med 2006;24:136–7.CrossRefGoogle ScholarPubMed
37.Fu, ES, Downs, JB, Schweiger, JW, et al. Supplement oxygen impairs detection of hypoventilation by pulse oximetry. Chest 2004;126:1552–8.CrossRefGoogle Scholar
38.Downs, JB. Prevention of hypoxemia: the simple, logical, but incorrect solution. J Clin Anesth 1994;6:180–1.CrossRefGoogle ScholarPubMed
39.Hutton, P, Clutton-Brock, T. The benefits and pitfalls of pulse oximetry. BMJ 1993;307:457–8.CrossRefGoogle ScholarPubMed
40.Davidson, JAH, Hosie, HE. Limitations of pulse oximetry: respiratory insufficiency — a failure of detection. BMJ 1993;307:372–3.CrossRefGoogle Scholar
41.Wiklund, L, Hok, B, Stahl, K, et al. Postanesthesia monitoring revisited: frequency of true and false alarms from different monitoring devices. J Clin Anesth 1994;6:182–8.CrossRefGoogle ScholarPubMed
42.Soto, RG, Fu, ES, Vila, H Jr, et al. Capnography accurately detects apnea during monitored anesthesia care. Anesth Analg 2004;99:379–82.CrossRefGoogle ScholarPubMed