When is Capnography Useful in the ED? Part I
- Aug 7th, 2017
- Brit Long
Author: Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC) and Michael Vivirito RN, CEN (Joint Base Elmendorf Richardson Medical Center, Emergency Medicine) // Edited by: Alex Koyfman, MD (@EMHighAK)
The EMS phone rings, with a crew bringing in a 62-year-old male in cardiac arrest. Initial rhythm was ventricular fibrillation, and they have provided two shocks. They arrive, your team transfers him over, compressions continue, and you check access and monitors. Of all the monitors you have, what is something that can not only prognosticate, but assess compression quality and suggest ROSC?
Capnography! This post will evaluate the literature behind several common uses of capnography in the ED: cardiac arrest, endotracheal tube (ETT) placement, and procedural sedation. Part II will evaluate several other uses of capnography in critical illness: trauma, sepsis, DKA, pulmonary pathology, and fluid responsiveness.
A Little Background
Capnography includes the noninvasive measurement of CO2 partial pressure during respiration (primarily exhalation). This can be displayed as a color (colorimetric or qualitative), number (quantitative), and as a function of time with waveform.1-8 A normal waveform displays several phases, and interpretation of this waveform can provide valuable information based on several features.1-9 More specifically, the quantitative monitor provides a numeric value which is the end-tidal carbon dioxide (EtCO2) plateau in phase III.
1) Verification and Monitoring of ETT
Capnography shines in verifying and monitoring ETT placement and position. In fact, it may be one of the most accurate means of confirming correct placement, other than direct visualization of the tube between the chords.7-9 Fogging and condensation of the ETT can occur in over 80% of esophageal intubations.10 Chest wall movement is not reliable, and neither are breath sounds (16% of esophageal intubations).10-12 Qualitative markers will turn yellow with tracheal placement and remain purple (except for several circumstances such as recent carbonated beverage, gastric fluids on the marker, etc.).1-4,9,13 Sensitivity approaches 100% for qualitative markers,14-19 and quantitative markers offer even more important information with four phases as described above.9,20-22 Quantitative capnography will still display the same findings with right mainstem bronchus intubation, as well as if the ETT is placed just above the hypopharynx (it will become erratic over time due to malpositioning). Flat waveforms are commonly seen in ETT obstruction, technical malfunction of the monitor or tubing, prolonged cardiac arrest, and complete airway obstruction distal to the ETT. 1-9,19 Sensitivity in cardiac arrest is 60-100%, which varies due to cause and duration of arrest.9,14-19
Monitoring ETT location during patient movement is vital to ensuring the ETT remains in the appropriate position. Dislodgement or misplacement may occur in up to 23% of transports not undergoing continuous capnography monitoring.23,24 Capnography should be used during transport of intubated patients to monitor for displacement.9,25,26
2) Cardiac Arrest
Capnography has been used since 1989 for cardiac arrest. The specific EtCO2 level is a reflection of cardiopulmonary blood flow, and the value correlates with cardiac output from chest compressions.9,19-23,27,28 The 2015 ACLS guidelines state quantitative waveform is recommended to monitor compressions and for ROSC.9 Depth and quality of compressions affect EtCO2. Compressions should target values greater than 10 mm Hg, with 20 mm Hg optimal. Decreases in EtCO2 suggest poor compression quality or another etiology that has not been treated (hemorrhage, pneumothorax, tamponade, myocardial infarction, among others).9,29,30
A rapid and abrupt increase in EtCO2 levels suggests ROSC, specifically levels 30-40 mm Hg or an increase of at least 10 mm Hg.31 A specific level is not recommended, but rather the sudden increase. With ROSC and a perfusing rhythm, cardiac output increases, resulting in EtCO2 increase. This could potentially be used to monitor for ROSC without pulse checks. If sudden increase in EtCO2 is observed, 9,19-23,30,31 rhythm assessment can be conducted,29,31-33 but chest compressions should be continued otherwise.
During CPR, EtCO2 can be used as a prognostic factor, though times vary. Literature has evaluated levels from 3 minutes onward, with most at 20 minutes. A value greater than 20 mm Hg is correlated with improved chance of ROSC and levels less than 10 mm Hg associated with decreased survival.28,29,34-42 One meta-analysis states levels of 25 mm Hg are strongly associated with ROSC.42 Increase in capnography in inpatient PEA arrest demonstrates OR 4.8 for ROSC.43 Another study found EtCO2 to have sensitivity and specificity to be 88% and 77%, respectively, for ROSC at 5 and 10 minutes.41 Currently, capnography should not be used in isolation to determine cause of arrest, prognosticate, or evaluate for ROSC. It can be used in association with other measures. One great review uses the mnemonic PQRST for capnography use in arrest.44
3) Procedural Sedation
A common ED use for capnography is procedural sedation, as it can detect hypoventilation earlier than pulse oximetry, especially with supplemental oxygen use. It can also monitor for upper airway obstruction, laryngospasm, and bronchospasm.45-54 Complications during sedation are rare, with one meta-analysis finding 5 out of 1000 patients requiring airway assistance.55 If respiratory depression or apnea occurs, EtCO2 will demonstrate elevated plateau levels with decreased breaths.45-54 ACEP has a Level B recommendation stating “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.”45
The literature varies on the advantages of capnography.56-60 A Cochrane review evaluating 1272 patients found capnography did not reduce clinically significant events, despite significant heterogeneity and bias.58 Airway repositioning did occur more frequently in capnography. Sivilotti et al. found no difference in capnography versus pulse oximetry for hypoxia detection.
Many studies support the utility of capnography in monitoring. Langhan et al. in 2015 found decreased hypoventilation and desaturation in patients undergoing capnography.61 Miner et al. in 2002 found capnography was able to detect all respiratory depressions, with pulse oximetry detecting one third.50 Burton et al. found capnography detected respiratory changes in 70% of cases before pulse oximetry,51 with Anderson et al. finding capnography diagnosed 100% before pulse oximetry.54 Vargo et al. found 100% sensitivity for capnography versus 50% for oximetry in detecting hypoventilation.53 A meta-analysis found capnography was over 17 times as likely to detect hypoventilation,49 and other studies suggesting it can decrease risk of hypoxia. One systematic review suggests capnography decreases hypoxemic episodes, with relative risk 0.71 (95% CI 0.56-0.91).62
Capnography allows emergency physicians to closely evaluate ventilation at the bedside based on the waveform and value, especially when supplemental oxygen is used.45,62,63 In settings where one provider is completing the procedure and sedation, capnography provides safety, as pulse oximetry alone demonstrates a response delay in tissue hypoxemia.45,63
Where does this leave us?
Waveform capnography is helpful in ETT verification and detection of displacement, cardiac arrest, and procedural sedation. Evaluation of the absolute value of end tidal levels and the waveform provides valuable information. Part II will evaluate other potential uses of waveform capnography including obstructive airway diseases, PE, trauma, sepsis, seizures, and fluid responsiveness. Stay tuned for more!
– Capnography involves the noninvasive measurement of CO2 partial pressure during respiration, displayed as qualitative or quantitative forms.
– A waveform depicts the respiratory cycle based on CO2 production, with end tidal CO2 the plateau in phase III.
– Waveform capnography possesses several key uses in the ED.
– Capnography is one of the most reliable means of assessing ETT placement and position. Other measures such as tube condensation, chest movement, and breath sounds are not reliable.
– Transport of the intubated patient should include waveform capnography to monitor ETT placement.
– Waveform capnography is useful to evaluate compression quality during CPR, monitor for ROSC, and as a tool for prognostication.
– Use of capnography in procedural sedation can assist in detecting hypoventilation when compared to pulse oximetry alone.
Acknowledgements: Thank you to Bhavani-Shankar Kodali, MD, of http://www.capnography.com/new/, for providing the figures for this post.
- Whitaker DK. Time for capnography – everywhere. Anaesthesia. 2011; 66:544–9.
- Kodali BS. Capnography outside the operating rooms. 2013 Jan;118(1):192-201.
- Nassar BS, Schmidt GA. Capnography During Critical Illness. 2016 Feb;149(2):576-85.
- Thompson JE, Jaffe MB. Capnographic waveforms in the mechanically ventilated patient. Respir Care. 2005 Jan;50(1):100-8; discussion 108-9.
- Blanch L, Romero PV, Lucangelo U. Volumetric capnography in the mechanically ventilated patient. Minerva Anestesiol. 2006 Jun;72(6):577-85.
- Zwerneman K. End-tidal carbon dioxide monitoring: a VITAL sign worth watching. Crit Care Nurs Clin North Am. 2006 Jun;18(2):217-25, xi.
- Manifold CA, Davids N, Villers LC, et al. Capnography for the nonintubated patient in the emergency setting. Journ Emerg Med 2013;45(4):626-32.
- Ward KR,Yealy DM. End-tidal carbon dioxide monitoring in emergency medicine, Part 1: Basic principles. Acad Emerg Med. 1998 Jun;5(6):628-36.
- Neumar RW, Shuster M, Callaway CW, et al. Part 1: Executive Summary: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2015;132(18 Suppl 2):S315–S367.
- Kelly JJ, Eynon CA, Kaplan JL, et al. Use of tube condensation as an indicator of endotracheal tube placement. Ann Emerg Med 1998; 31:575.
- Birmingham PK, Cheney FW, Ward RJ. Esophageal intubation: a review of detection techniques. Anesth Analg 1986; 65:886.
- Pollard BJ, Junius F. Accidental intubation of the oesophagus. Anaesth Intensive Care 1980; 8:183.
- Bozeman WP, Hexter D, Liang HK, Kelen GD. Esophageal detector device versus detection of end-tidal carbon dioxide level in emergency intubation. Ann Emerg Med 1996; 27:595.
- Silvestri S, Ralls GA, Krauss B, et al. The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system. Ann Emerg Med 2005; 45:497.
- Goldberg JS, Rawle PR, Zehnder JL, et al. Colorimetric end-tidal carbon dioxide monitoring for tracheal intubation. Anesth Analg 1990;70:191-4.
- Anton WR, Gordon RW, Jordon TM, et al. A disposable end-tidal CO2 detector to verify endotracheal intubation. Ann Emerg Med 1991;20:271–5.
- Kelly JS, Wilhoit RD, Brown RE, et al. Efficacy of the FEF colourimetric end-tidal carbon dioxide detector in children. Aneth Analg 1992;75:45–50.
- Puntervoll SA, Soreide E, Jacewicz W, et al. Rapid detection of oesophageal intubation: take care when using colourimetric capnometry. Acta Anaesthesiol Scand 2002;46:455–7.
- Varon AJ,Morrina J, Civetta JM. Clinical utility of a colorimetric end-tidal CO2 detector in cardiopulmonary resuscitation and emergency intubation. J Clin Monit. 1991 Oct;7(4):289-93.
- Falk JL, Rackow EC, Weil MH. End-tidal carbon dioxide concentration during cardiopulmonary resuscitation. N Engl J Med 1988; 318:607.
- Garnett AR, Ornato JP, Gonzalez ER, Johnson EB. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. JAMA 1987; 257:512.
- Sheak KR, Wiebe DJ, Leary M, et al. Quantitative relationship between end-tidal carbon dioxide and CPR quality during both in-hospital and out-of-hospital cardiac arrest. Resuscitation 2015; 89:149.
- Bhende MS, Thompson AE. Evaluation of an end-tidal CO2 detector during pediatric cardiopulmonary resuscitation. Pediatrics 1995; 95:395.
- [No authors listed]. End-tidal carbon dioxide measurement in emergency medicine and patient transport. Health Devices.1991 Feb;20(2):35-72.
- Fanara B, Manzon C, Barbot O, Desmettre T, Capellier G. Recommendations for the intra-hospital transport of critically ill patients. Crit Care. 2010;14:R87.
- Bhende MS,Thompson AE, Orr RA. Utility of an end-tidal carbon dioxide detector during stabilization and transport of critically ill children. 1992 Jun;89(6 Pt 1):1042-4.
- Davis DP, Sell RE, Wilkes N, et al. Electrical and mechanical recovery of cardiac function following out-of-hospital cardiac arrest. Resuscitation 2013; 84:25.
- Sanders AB, Kern KB, Otto CW, et al. End-tidal carbon dioxide monitoring during cardiopulmonary resuscitation. A prognostic indicator for survival. JAMA 1989; 262:1347.
- Steedman DJ, Robertson CE. Measurement of end-tidal carbon dioxide concentration during cardiopulmonary resuscitation. Arch Emerg Med. 1990;7(3):129-134.
- Heradstveit BE, Sunde K, Sunde GA, Wentzel-Larsen T, Heltne JK. Factors complicating interpretation of capnography during advanced life support in cardiac arrest—a clinical retrospective study in 575 patients. Resuscitation. 2012;83(7):813-818.
- Lui CT,Poon KM, Tsui KL. Abrupt rise of end tidal carbon dioxide level was a specific but non-sensitive marker of return of spontaneous circulation in patient with out-of-hospital cardiac arrest. 2016 Jul;104:53-8.
- Pokorná M, Necas E, Kratochvíl J, et al. A sudden increase in partial pressure end-tidal carbon dioxide (P(ET)CO(2)) at the moment of return of spontaneous circulation. J Emerg Med. 2010;38(5):614-621.
- Paradis NA, Martin GB, Rivers EP, et al. Coronary perfusion pressure and the return of spontaneous circulation in human cardiopulmonary resuscitation. JAMA. 1990;263(8):1106-1013.
- Bullock A,Dodington JM, Donoghue AJ, et al. Capnography Use During Intubation and Cardiopulmonary Resuscitation in the Pediatric Emergency Department. Pediatr Emerg Care. 2016 Jul 23. [Epub ahead of print]
- Chen J-J, Lee Y-K, Hou S-W, et al. End-tidal carbon dioxide monitoring may be associated with a higher possibility of return of spontaneous circulation during out-of-hospital cardiac arrest: a population-based study. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine. 2015;23:104.
- Murphy RA,Bobrow BJ, Spaite DW, et al. Association between Prehospital CPR Quality and End-Tidal Carbon Dioxide Levels in Out-of-Hospital Cardiac Arrest. Prehosp Emerg Care. 2016 May-Jun;20(3):369-77.
- Levine RL, Wayne MA, Miller CC. End-tidal carbon dioxide and outcome of out-of-hospital cardiac arrest. N Engl J Med 1997; 337:301.
- Wayne MA, Levine RL, Miller CC. Use of end-tidal carbon dioxide to predict outcome in prehospital cardiac arrest. Ann Emerg Med 1995; 25:762.
- Grmec S, Klemen P. Does the end-tidal carbon dioxide (EtCO2) concentration have prognostic value during out-of-hospital cardiac arrest? Eur J Emerg Med 2001; 8:263.
- Poon KM,Lui CT, Tsui KL, et al. Prognostication of out-of-hospital cardiac arrest patients by 3-min end-tidal capnometry level in emergency department. 2016 May;102:80-4.
- Einav S, Bromiker R, Weiniger CF, Matot I. Mathematical modeling for prediction of survival from resuscitation based on computerized continuous capnography: Proof of concept. Acad Emerg Med 2011; 18:468–75.
- Hartmann SM,Farris RW, Di Gennaro JL, et al. Systematic Review and Meta-Analysis of End-Tidal Carbon Dioxide Values Associated With Return of Spontaneous Circulation During Cardiopulmonary Resuscitation. J Intensive Care Med. 2015 Oct;30(7):426-35.
- Pearce AK,Davis DP, Minokadeh A, et al. Initial end-tidal carbon dioxide as a prognostic indicator for inpatient PEA arrest. 2015 Jul;92:77-81.
- Heradstveit BE,Heltne JK. PQRST – a unique aide-memoire for capnography interpretation during cardiac arrest. 2014 Nov;85(11):1619-20.
- Clinical Policy: Procedural Sedation and Analgesia in the Emergency Department. Ann Emerg Med. 2014;63:247-258.
- Lightdale JR, Goldmann DA, Feldman HA, et al. Microstream capnography improves patient monitoring during moderate sedation: a randomized, controlled trial. Pediatrics. 2006;117:e1170-e1178.
- Qadeer MA, Vargo JJ, Dumot JA, et al. Capnographic monitoring of respiratory activity improves safety of sedation for endoscopic cholangiopancreatography and ultrasonography. Gastroenterology. 2009;136:1568-1576.
- 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;55:258-264.
- Waugh JB, Epps CA, Khodneva YA. Capnography enhances surveillance of respiratory events during procedural sedation: a meta-analysis. J Clin Anesth. 2011;23:189-196.
- Miner JR, Heegaard W, Plummer D. End-tidal carbon dioxide monitoring during procedural sedation. Acad Emerg Med. 2002;9:275-280.
- 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;13:500-504.
- 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;52:1-8.
- Vargo JJ, Zuccaro G, 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;55:826-831.
- Anderson JL, Junkins E, Pribble C, et al. Capnography and depth of sedation during propofol sedation in children. Ann Emerg Med. 2007;49:9-13.
- Bellolio MF, Puls HA, Anderson JL, et al. Incidence of adverse events in paediatric procedural sedation in the emergency department: a systematic review and meta-analysis. BMJ Open 2016;6:e011384.
- Dewdney C,MacDougall M, Blackburn R, et al. Capnography for procedural sedation in the ED: a systematic review. Emerg Med J. 2016 Aug 26. pii: emermed-2015-204944.
- Mohr NM, Stoltze A, Ahmed A, et al. Using continuous quantitative capnography for emergency department procedural sedation: a systematic review and cost-effectiveness analysis. Intern Emerg Med. 2016 Dec 28. doi: 10.1007/s11739-016-1587-3.
- Wall BF, Magee K, Campbell SG, et al. Capnography versus standard monitoring for emergency department procedural sedation and analgesia. Cochrane Database Syst Rev. 2017 Mar 23;3:CD010698.
- Campbell SG, Magee KD, Zed PJ, et al. End-tidal capnometry during emergency department procedural sedation and analgesia: a randomized, controlled study. World Journal of Emergency Medicine. 2016;7(1):13-18.
- 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;12:397-404.
- Langhan ML, Shabanova V, Li F-Y, et al. A Randomized Controlled Trial of Capnography During Sedation in a Pediatric Emergency Setting. The American journal of emergency medicine. 2015;33(1):25-30.
- Conway A,Douglas C, Sutherland JR, et al. A systematic review of capnography for sedation. 2016 Apr;71(4):450-4.
- Hamber EA, Bailey PL, James SW, et al. Delays in the detection of hypoxemia due to site of pulse oximetry probe placement. J Clin Anesth. 1999; 11: 113–118.