- 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
- 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)
- 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)
- 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
Cardiac Arrest Monitoring
Ensure adequate chest compressions
- ETCO2 10-20mmHg signifies high quality chest compressions
- Attaining ROSC is associated with an ETCO2 jump 10mmHg with ROSC (13.5 on average)
- 10mHg has a sensitivity of 33% and a specificity of 97% for ROSC
- 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
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
- Adults with BG>550
- ETCO2>35 mmHg has a sensitivity 100%, ETCO2<26 mmHg has specificity of 96%
- Adults with BG>250
- ETCO2>24.5 mmHg has sensitivity of 90%, ETCO2<24.5 mmHg has specificity of 90%
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- 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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- Soleimanpour H, Taghizadieh A, Niafar M, Rahmani F, Golzari SE, Esfanjani RM. Predictive value of capnography for suspected diabetic ketoacidosis in the emergency department. West J Emerg Med. 2013 Nov;14(6):590-4. doi: 10.5811/westjem.2013.4.14296.