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Three Part Question

In [a patient undergoing procedural sedation], does [the use of capnogrpahy] [reduce adverse respiratory events]?

Clinical Scenario

A 35 year old man has a dislocated shoulder that will need to be reduced. He will require sedation and will be monitored with standard monitoring (ECG, BP, SpO2). You wonder if addition of capnography would be beneficial for the patient?

Search Strategy

Ovid MEDLINE 1948 to November Week 2 2011
(sedation.mp) AND (Capnog$.mp or (end tidal adj2(carbon dioxide or CO2)))

The Cochrane library November 2011: MeSH descriptor Capnography.

Search Outcome

202 papers were identified 9 of which were relevant.
Papers were excluded if they were not prospective studies and not undertaken in the Emergency Department (ED).

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Wright SW 1992 USA	9 of 27 adults undergoing procedural sedation in an ED. Monitored with both standard monitoring and capnography. Respiratory depression defined as SpO2 <90%.	Prospective observational	ETCO2	8/9 hypoxic patients had a rise in ETCO2 a few seconds before desaturation.	Small patient numbers. Nasal sampling used.
Hart LS et al 1997 USA	8 of 42 children undergoing procedural sedation in an ED. SpO2 and ETCO2 were continuously recorded. Respiratory depression defined as SpO2<90% for >1 min, ETCO2 ≥50 mm Hg.	Prospective observational	Hypercarbia only	6/8	Small patient numbers. Nasal sampling
			Hypercarbia and hypoxia	2/8
Miner JR et al 2002 USA	33 of 74 adults undergoing procedural sedation in an ED. Monitored with standard monitoring and capnography. Respiratory depression defined as: SpO2<90% for >1 min, ETCO2 ≥50 mm Hg, absent ETCO2 waveform.	Prospective observational	SpO2≤90%	11/33	Small patient numbers
			Absent ETCO2 waveform	11/33
			ETCO2 >50 mm Hg	24/33
Burton JH et al 2006 USA	20 of 59 adults and children (60 procedures) undergoing procedural sedation in an ED were monitored with standard monitoring and capnography. The clinical team were blinded. Acute respiratory event defined as: SpO2≤92%, Increase in supplemental O2, ETCO2 increase ≥10 mm Hg from baseline, ETCO2 ≤30 mm Hg, ETCO2 ≥50 mm Hg.	Prospective observational	SpO2≤92%	19/20	Data recording. Convenience sample. Small patient numbers. Study terminated early.
			Abnormal ETCO2 readings.	16/19 hypoxic episodes
			ETCO2 findings documented before changes in SpO2	14/20
Anderson JL 2007 USA	125 children undergoing procedural sedation in an ED with propofol were monitored with standard monitoring and capnography. Respiratory events monitored were: Hypoxemia - SpO2<90%, Hypercarbia - ETCO2>50 mm Hg, ETCO2 increase >10 mm Hg from baseline, Apnoea: cessation of spontaneous ventilation for 30 s, Absent ETCO2 waveform and adverse airway events.	Prospective observational	Hypoxemia	6 episodes.	Convenience sample. Nasal sampling.
			Hypercarbia:	31 children. 7 required an intervention.
			Apnoea:	5 patients became apnoeic. Capnography detected all 5 patients before pulse oximetry or clinical examination.
			Adverse airway event	9 patients developed airway obstruction and 5 had a hypoxic event. Capnography identified 6 of the 9 before pulse oximetry or clinical examintaion.
Deitch K et al 2007 USA	39 of 80 adults and children undergoing procedural sedation in an ED monitored with standard monitoring and capnography. Respiratory depression defined as: SpO2<90%, ETCO2>50 mm Hg, ETCO2 change from baseline >10 mm Hg, loss of ETCO2 waveform.	RCT	SpO2<90%	11/80	Investigating the use of capnography was not the primary aim. Study terminated early after enrollment of 80 patients due to lower than expected incidence of hypoxia.
			ETCO2 changes with hypoxia.	7/11
			ETCO2 changes without hypoxia.	28/80
			Physician identification of respiratory depression.	8/11 hypoxic patients and 0/28 who did not become hypoxic
Deitch K et al 2008 USA	110 adults undergoing procedural sedation in an ED. Patients were monitored with standard monitoring and capnography. Physicians were blinded. Respiratory depression was defined as SpO2<93%, ETCO2>50 mm Hg, ETCO2 change from baseline >10 mm Hg, Loss of ETCO2 waveform.	RCT	Hypoxia	25/100	Investigation of the use of capnography was not the primary aim. Definition of hypoxia.
			Absolute ETCO2 change≥10 mm Hg.	18/25 patients who experienced hypoxia
			Clinical utility of absolute ETCO2 change≥10 mm Hg.	Sensitivity 72% (59% to 93%). Specificity 47% (36% to 58%)
			Physician identification of respiratory depression.	Physician identified respiratory depression in 23/25 patients who became hypoxic. Physician identified respiratory depression in 1/27 that met ETCO2 criteria but did not become hypoxic.
Deitch K et al 2010 USA	132 adults undergoing procedural sedation in the ED were randomly assigned to study group (standard monitoring and capnography) or control group (standard monitoring and blinded capnography). Aimed to show 15% decrease in hypoxia from a presumed baseline of 20% when capnography used. 72 patients required in each arm. Hypoxia defined as SpO2<93% for 15+ s. Respiratory depression defined as ETCO2≥50 mm Hg, ETCO2 increase or decrease from baseline ≥10%, Loss of waveform ≥15 s. Capnography versus standard monitoring.	RCT	Hypoxia	17/68 vs 27/64 (p=0.035)	Underpowered.
			Respiratory depression	All 44 patients who developed hypoxia first exhibited respiratory depression.
			Clinical utility of respiratory depression	32 patients exhibited respiratory depression but did not develop hypoxia. Sensitivity 100% [90% to 100%] Specificity 64% (53% to 73%)).
Sivilotti ML et al 2010 Canada	63 patients undergoing procedural sedation were monitored continuously with capnography and standard monitoring. Hypoxia defined as SpO2<92%. Abnormal capnometry defined as hypoventilation, ETCO2 >50 mm Hg, increase or decrease of 10 mm Hg from baseline, loss of waveform.	RCT	Hypoxia	36(57%)	Investigation of the use of capnography was not the primary aim. Study terminated early. Lack of information on study design. Not blinded to capnography. Data recording.
			Abnormal capnometry	30 (38%) patients showed abnormal capnography
			Hypoventilation	21/36 hypoxic patients had abnormal capnography. 2/21 preceded desaturation. 19 patients exhibited hypoventilation. Hypoventilation did not precede desaturation in the12 patients in whom both events occurred.

Comment(s)

Deitch et al in 2010 published the only well-designed RCT with the primary aim of investigating the use of capnography during procedural sedation in the ED. This study demonstrated a statistically significant decrease in hypoxic events with the use of capnography. It suggested an ability to anticipate hypoxic events with capnography. The majority of the published evidence recognises that respiratory events do occur during procedural sedation and that there is a relatively high level of subclinical respiratory depression only evident with ETCO2 monitoring. They also recognise that a large number of these patients remain otherwise well. Most of the studies agree that those who become hypoxic exhibit ETCO2 changes before pulse oximetry changes. These changes in the ETCO2 could act as an early warning allowing the physician to assess the situation and take action as required. The paper by Sivilotti et al however, disagrees with the other studies with regards to the timing of changes in the ETCO2 and pulse oximetry. In their conclusion though, they state that this is only applicable in patients not receiving supplemental oxygen and it may in fact be a very useful monitor in patients receiving oxygen.

Clinical Bottom Line

Capnography may provide early warning of ventilatory changes that could result in hypoxia.

References

1. Wright SW Conscious sedation in the emergency department: the value of capnography and pulse oximetry. Ann Emerg Med. 1992 May;21(5):551-555.
2. 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 Jun;13(3):189-193.
3. Miner JR, Heegaard W, Plummer D End-tidal carbon dioxide monitoring during procedural sedation. Acad Emerg Med. 2006 May;13(5):500-504.
4. 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. 2002 Apr;9(4):275-280.
5. Anderson JL, Junkins E, Pribble C et al. Capnography and depth of sedation during propofol sedation in children Ann Emerg Med. 2007 Jan;49(1):9-13.
6. 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 Jan;49(1):1-8.
7. 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 Jul;52(1):1-8.
8. Deitch K, Miner J, 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 Mar;55(3):258-264.
9. Sivilotti ML, Messenger DW, van Vlymen J, et al. A comparative evaluation of capnometry versus pulse oximetry during procedural sedation and analgesia on room air. CJEM 2010 Sep;12(5):397-404.