2nd April 2024

Waveform capnography

Carbon dioxide (CO₂) is a byproduct of metabolism and is expired during respiration. It can be measured using capnography to monitor the concentration of CO₂ in expired gas. The highest concentration is at the end of expiration, termed end-tidal CO₂. The end-tidal CO₂ is the partial pressure of CO₂ at the end of every exhaled breath and reflects cardiac output and pulmonary blood flow. Waveform capnography enables continuous end-tidal CO₂ monitoring during CPR. It can be used to ensure that the endotracheal tube is in the correct position. It is a reliable method to identify ROSC when the end tidal volume significantly rises. During CPR, it can monitor the ventilation rate and avoid hyperventilation. As well as this, it can monitor the quality of chest compressions as end-tidal CO₂ values are associated with compression depth and ventilation rate.

Image Source: Wikimedia Commons (2024). Capnography, Licensed under a creative commons licence. Available for free at: https://en.wikipedia.org/wiki/Capnography (Accessed: 12 March 2024).

References

• Resuscitation Council UK. 2021 Resuscitation Guidelines. Available from https://www.resus.org.uk/library/2021- resuscitation-guidelines
• Tidy, C. (2023) Cardiopulmonary arrest in adults: Doctor, Patient.info. Edited by P. Vincent. Available at: https://patient.info/doctor/adult-cardiopulmonary-arrest
• Dee R, Smith M, Rajendran K. International Liaison Committee on Resuscitation Basic Life Support Task Force Collaborators. The effect of alternative methods of cardiopulmonary resuscitation – Cough CPR, percussion pacing or precordial thump – on outcomes following cardiac arrest. A systematic review. Resuscitation. 2021 May;162:73-81. doi: 10.1016/j.resuscitation.2021.01.027. Epub 2021 Feb 11. PMID: 33582257.
• Wu JP, Gu DY et al. Good neurological recovery after rescue thrombolysis of presumed pulmonary embolism despite prior 100 minutes CPR. J Thorac Dis. 2014 Dec;6(12):E289-93. doi: 10.3978/j.issn.2072-1439.2014.12.23. PMID: 25590010; PMCID: PMC4283306.
• European Resuscitation Council Guidelines 2021: Adult advanced life support. Resuscitation. 2021 Apr:161:115-151.