Capnography

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Background

  • End-tidal CO2 monitors can be qualitative or quantitative
    • Qualitative include calorimety devices (CO2 = blue, No CO2 = yellow)
    • Quantitative include devices that give numeric values
      • Mainstream (or inline) CO2 monitors are placed within the closed circuit of the ventilator (or BVM)
      • Sidestream CO2 monitors use special NC to detect CO2

Basics

  • Capnography measures the amount of exhaled CO2
  • ETCO2 of 35-45mmHg is considered normal
    • <35mmHg = Hypocapnia or Hyperventilation
    • >45mmHg = Hypercapnia or Hypoventilation
  • Directly measure the function of ventilation (not oxygenation)
    • ETCO2 ≥ PCO2
  • Indirectly measures overall metabolism (or lack there of in cardiac arrest)

Capnogram Overview

Typical waveform of a capnogram

  • Exhalation will first expel dead space air (Phase I)
  • Then a rapid rise in CO2 rich air is noted (Phase II)
  • This is followed by a more gradual increase in CO2 (Phase III)
  • The curve peaks at the end of Phase III which is noted as the End-Tidal CO2 measurement
  • Inhalation follows (Phase 0 or IV)


Airway Monitoring

  • Ensure adequate BVM ventilation
  • Assess for ETT placement using presents of measurable ETCO2 and waveform
    • In out of hospital use, this had SN 1.0 and SP 1.0 in detected good placement[1]

Cardiac Arrest Monitoring

Ensure adequate chest compressions

  • ETCO2 10-20mmHg signifies high quality chest compressions[2]

ROSC

  • Attaining ROSC is associated with an ETCO2 jump 10mmHg with ROSC (13.5 on average)[3]
    • 10mHg has a sensitivity of 33% and a specificity of 97% for ROSC[4]
    • 20mHg has a sensitivity of 20% and a specificity of 99% for ROSC
  • CPR does not have to be stopped for pulse checks
  • Loss of ROSC can be determined by a significant drop signifies drop in ETCO2

Prognosis

  • ETCO2 level of 10mmHg or less after 20 min of CPR predicts death[5][6]

Procedural Sedation Monitoring

  • Pulse-ox has a lag time of sec to mins
  • Capnography will show real-time respiratory changes and apnea
  • ETCO2 monitoring detects clinically signifcant respiratory events before SPO2 or clinically noted apnea/hypoventilation[7]


See Also

Intubation Procedural sedation

External Links

http://www.capnography.com/

References

  1. ↑ Silvestri, S, 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(5):497-503.
  2. ↑ Kodali, BS, et al. Capnography during cardiopulmonary resuscitation: Current evidence and future directions. J Emerg Trauma Shock. 2014; 7(4):332–340.
  3. ↑ Grmec, S, et al.Utstein style analysis of out-of-hospital cardiac arrest--bystander CPR and end expired carbon dioxide. Resuscitation. 2007; 72(3):404-14.
  4. ↑ Tat LC, Ming PK, Leung TK. 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. Resuscitation. 2016; 104:53–58.
  5. ↑ Eckstein, M, et al. End-Tidal CO2 as a Predictor of Survival in Out-of-Hospital Cardiac Arrest. Prehospital and Disaster Medicine. 2011; 26(3):148-150.
  6. ↑ Levine, R, End-tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest. NEJM.1997. 337(5):301-6.
  7. ↑ Burton, JH, et al. Does End-Tidal Carbon Dioxide Monitoring Detect Respiratory Events Prior to Current Sedation Monitoring Practices. Academic Emergency Medicine. 2006; 13:500–504.
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