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
- 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]
- 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
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[6]
See Also
Intubation Procedural sedation
External Links
References
- ↑ 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.
- ↑ Kodali, BS, et al. Capnography during cardiopulmonary resuscitation: Current evidence and future directions. J Emerg Trauma Shock. 2014; 7(4):332–340.
- ↑ 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.
- ↑ 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.
- ↑ Levine, R, End-tidal Carbon Dioxide and Outcome of Out-of-Hospital Cardiac Arrest. NEJM.1997. 337(5):301-6.
- ↑ 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.