Should End-Tidal Capnometry (ETC) During ED Procedural Sedation/Analgesia (PSA) Not Be Standard Care?

Background: Procedural sedation and analgesia (PSA) is a frequently employed in the emergency department (ED) to facilitate painful procedures. Some of the potential untoward effects of PSA include cardio-respiratory depression and/or airway compromise.  Standard practice in many parts of the world includes non-invasive pulse oximetry as well as end-tidal capnometry (ETC) for patient monitoring. ETC gives the benefit of identification of respiratory depression, airway obstruction, and apnea earlier than pulse oximetry alone allowing for a greater safety margin when monitoring these patients.  While the use of both monitoring modalities makes sense, there is limited data on the benefit to patients.

Paper: Campbell SG et al. End-Tidal Capnometry During Emergency Department Procedural Sedation and Analgesia: A Randomized, Controlled Study. World J Emerg Med 2016. PMID: 27006732

Clinical Question: Does end-tidal capnometry (ETC) plus usual care in patients undergoing procedural sedation and analgesia (PSA) in the emergency department (ED) decrease respiratory adverse events compared to usual care alone?

What They Did:

  • Single-center, prospective, randomized, non-blinded trial
  • PSA performed by senior paramedic acute care practitioners (ACPs) with additional training in PSA (Including ETC interpretation)
    • ACPs were instructed to use their clinical judgment to intervene clinically in response to ETC or pulse oximetry changes as they felt appropriate
    • Paramedics were permitted to select medications for PSA as well as doses and methods of titration
    • IV fluids was left to the discretion of the paramedic
  • Patients undergoing PSA were randomized to:
    • Usual care alone
    • ETC + usual care
  • Usual care:
    • Pre-procedure IV analgesia when indicated
    • Informed patient consent
    • Continuous O2 therapy
    • Cardiac and pulse oximetry monitoring
    • Blood pressure measurement q5min during the procedure


  • Primary: Respiratory adverse events:
    • Airway repositioning maneuver
    • Positive pressure (BVM) ventilation
    • Oral/nasal airway placement
    • Endotracheal intubation
    • Oxygen desaturation (SaO2 of <90% for 30sec)
  • Secondary:
    • Level of sedation greater than intended (overshoot)
    • Hypotension
    • Sedation time (Time from the first dose of drug to commencement of procedure)
    • Recovery time (Time from the end of procedure to cessation of monitoring
    • Procedure success
    • Patient satisfaction


  • All patients age ≥16 years
  • Undergoing PSA


  • Unable to give consent
  • Critically ill
  • Required immediate endotracheal intubation


  • 986 patients enrolled
    • Usual care alone: 501pts
    • ETC + Usual care: 485pts
    • Female: 48%
    • Mean age: 46 years
    • Procedures
      • Orthopedic manipulation: 71%
      • Cardioversion: 12%
      • Abscess I&D: 12%
    • Sedation: Propofol (95%) used for most patients
      • Mean propofol dose: 142mg
    • Analgesia: Fentanyl used for most patients
    • 973pts (98.7%) of patients received oxygen therapy
      • NRB: 958pts
      • NC: 15pts
    • Respiratory Adverse Events (Primary Outcome)
      • SpO2 < 90%
        • ETC + UC: 1.9%
        • UC Alone: 1.4%
      • Airway Repositioning
        • ETC + UC: 26.2%
        • UC Alone: 18.4%
      • Positive Pressure Ventilation (with BVM)
        • ETC + UC: 0.0%
        • UC Alone: 0.4%
        • P = 0.164 (No STATISTICAL DIFFERENCE)
      • Oral/Nasal Airway
        • ETC + UC: 0.2%
        • UC Alone: 0.2%
      • Hypotension (SBP <100mmHg or <85mmHg if baseline SBP <100mmHg)
        • ETC + UC: 3.3%
        • UC Alone: 1.4%
        • P = 0.048
      • No Adverse Events
        • ETC + UC: 87.0%
        • UC Alone: 92.8%
        • P = 0.002
      • No difference in time taken for the procedure, vomiting, arrhythmia, degree of “overshoot”, and patient satisfaction post PSA


  • Asks a clinically important question
  • ASA scores, height, weight, and age were similar between groups
  • Utilized sedative drugs were similar between groups (including dosages)
  • Consecutive patients undergoing PSA (Only excluded patients not able to give consent or requiring immediate intubation)


  • Single center trial that may affect generalizability to other institutions
  • There were 5 primary outcomes (Usually there is only one)
  • PSA medication dosing regimens were not standardized between groups
  • 95% of the patients included in the trial received propofol for sedation. These results may not extrapolate to longer acting agents (i.e. ketamine)
  • It’s unclear what the duration of procedures was in this trial. Would these results be the same in patients requiring longer PSA (i.e. there was almost no SpO2 <90% in this trial)?
  • The group of clinicians and the training of those clinicians providing PSA in this trial may be different than other institutions


  • A device that warns clinicians earlier that their patients’ respirations are suppressed is a good thing, but a device that adds complexity to a procedure without improving patient outcome might distract clinicians from more important clinical monitoring (i.e. increased hypotension in the ETC arm of the trial)
    • Was sedation/analgesia given more aggressively in the ETC cohort due to a sense of increased security? A feeling of safety about respiratory status could have led to less vigilance about blood pressure monitoring
    • On the other hand the increase in airway repositioning in the ETC group suggests earlier response to hypoventilation, but the diagnosis of transient hypoventilation may also increase the use of PPV which can cause decreased venous return, insufflate the stomach and increase chances of aspiration (did not occur in this study)
    • Momentary apnea in the setting of good pre-oxygenation is likely to correct itself spontaneously as the drug wears off (i.e. shorter procedures)
  • Apnea is common during PSA and ETC does detect this earlier and more accurately than pulse oximetry alone. (we can’t take a single study in a bubble and have to look at all the evidence before coming to a conclusion of best practice)
    • Anesth Analg 2004 [2]: Apnea >20s occurred in 26% of cases all of whom were diagnosed by capnography while none detected by provider monitoring patient
    • Acad Emerg Med 2002 [3]: Respiratory depression occurred in 45% of patients but only 33% were detected by pulse oximetry alone
    • Acad Emerg Med 2006 [4]: Stopped trial after 20 out of 60 PSA patients suffered from respiratory depression. Abnormal ETC were documented in 14 of these patients before changes in pulse oximetry or clinically observed hypoventilation
    • There are more trials out there on this topic that all show the same thing…ETC does a better job of detecting respiratory depression compared to pulse oximetry alone or by provider monitoring [5][6]
    • ACEP 2023 Guidelines on PSA also recommend “Capnography may be used as an adjunct to pulse oximetry and clinical assessment to detect hypoventilation and apnea earlier than pulse oximetry and/or clinical assessment alone in patients undergoing procedural sedation and analgesia in the ED (Level B Recommendation).”
  • Despite all the above evidence and recommendations, there is not clear evidence that detecting respiratory depression is clinically important (i.e. transient respiratory depression vs actual hypoxemia vs patient-oriented outcomes of anoxic brain injury). That being said, although it may be the rare occurrence where detecting respiratory depression is important, this would argue to still consider broad application of ETC during PSA
  • This was a single center trial which may not extrapolate to other institutions
    • PSA was performed by senior paramedic acute care practitioners (ACPs)
    • All ACPs had additional training in interpretation of ETC
    • As this was a single center study there could also be a Hawthorne effect (Modification of behaviors in response to awareness of being observed)

Author Conclusion: “The addition of ETC does not appear to change any clinically significant outcomes. We found an increased incidence of the use of airway repositioning maneuvers and hypotension in cases where ETC was used.  We do not believe that ETC should be recommended as a standard of care for the monitoring of patients undergoing PSA.”

Clinical Take Home Point: I would be very careful taking this one, single center study, that primarily used propofol as its sedative agent (short duration of action/short procedures) and extrapolating that to all PSAs.  I would still recommend the use of ETC during all PSAs.


  1. Campbell SG et al. End-Tidal Capnometry During Emergency Department Procedural Sedation and Analgesia: A Randomized, Controlled Study. World J Emerg Med 2016. PMID: 27006732
  2. Soto RG et al. Capnography Accurately Detects Apnea During Monitored Anesthesia Care. Anesth Analg 2004. PMID: 15271710
  3. Miner JR et al. End-Tidal Carbon Dioxide Monitoring During Procedural Sedation. Acad Emerg Med 2002. PMID: 11927449
  4. Burton JH et al. Does End-Tidal Carbon Dioxide Monitoring Detect Respiratory Events Prior to Current Sedation Monitoring Practices? Acad Emerg Med 2006. PMID: 16569750
  5. Deitch K et al. The Utility of Supplemental Oxygen During Emergency Department Procedural Sedation with Propofol: A Randomized, Controlled Trial. Ann Emerg Med 2008. PMID: 18294729
  6. Deitch K et al. The Utility of Supplemental Oxygen During Emergency Department Procedural Sedation and Analgesia with Midazolam and Fentanyl: A Randomized, Controlled Trial. Ann Emerg Med 2007. PMID: 16978741

Post Peer Reviewed By: Anand Swaminathan, MD (Twitter/X: @EMSwami)

Cite this article as: Salim Rezaie, "Should End-Tidal Capnometry (ETC) During ED Procedural Sedation/Analgesia (PSA) Not Be Standard Care?", REBEL EM blog, June 27, 2024. Available at:

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