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Measuring CO2 Levels During Anesthetic Procedures

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Measuring CO2 Levels During Anesthetic Procedures

What is Capnometry?

Capnometry measures the level of cardon dioxide exhaled by the patient in one breath. This is measured using capnography which plots the values on a graph that is displayed as amount of CO2 exhaled over time. The normal range in a healthy individual is 35mmHg to 45mmHg.

Why use Capnometry during procedures?

Capnometry a useful way to verify adequate ventilation, this improves patient safety during sedation by reducing serious side effects related to hypoxemia (low oxygen levels) which can lead to neurological damage and in severe cases death. During procedures that require forms of sedation they carry the risk of respiratory depression (slow shallow breaths). While oxygen saturation is also a great tool for monitoring the status of your patient, capnography gives the clinician a deeper insight of the patient’s perfusion, respiratory patterns/trends, alveolar ventilation, and CO2 build up in the patient circuit. The photos below show some common patterns that can be encountered during sedation and early recognition of these patterns leads to better patient outcomes.

*Photos from kidocs.org/2013/11/much-hot-gas-etco2-non-anaesthetists/

Having your CO2 module calibrated during your yearly preventative maintenance

For most units during the preventative maintenance procedure, we start by allowing the CO2 module to warm up, this can sometimes take a few minutes. In that time if your machine has a removable and disposable water trap we can replace that for you. The next step is to zero the sensor to room air, once the zeroing process has completed, we then expose the sensor to a gas mixture with a specified CO2 percentage based on manufacturer’s requirements. The final step is to verify the calibration was successful by exposing the sensor again outside of the calibration to ensure it is reading correctly.

At TRH Services we have a wide variety of calibration gas on hand since not all machines and manufacturer’s use the same concentrations and balance gases. We also carry a variety of water traps and filters for your convenience.


Equipment Commonly Tested by TRH  Services:

Equipment Test

Manufacturer Field

Model Number Field

IMI NorgrenR06-221-NNEA
Western EnterprisesM1-320-PG
Drager Medical AG & Co. KGScio Four OxiPlus
Masimo CorporationEMMA (REF 605102)
Ordion Medical 1987 LTD.CapnoStream 20
Ordion Medical 1987 LTD.Microcap
Datex-OhmedaCardiocap 5 (F-CM1-04)
Edan Instruments Inc.IM50
Edan Instruments Inc.iM60
GE Medical Systems Information Technologies Inc.DASH 3000
Midmark Corporation9500 HD
Mindray Co. LTD.ACCUTORR 7
Mindray Co. LTD.Passport 8
Mindray Co. LTD.Passport 8 (6104F-PA00001)
Mindray Co. LTD.Passport 8 (6104F-PA00012)
Sharn Veterinary Inc.9500-HD
Welch AllynProPaq CS (242)
Edan Instruments Inc.iM50
Mindray Co. LTD.6104F-PA00012 – Passport 8
Datex-OhmedaCardiocap 5
Ordion Medical 1987 LTD.CapnoStream 20
Smiths Medical ASD INC.Capnocheck 2


Written: Caitlin Vanderkwaak
Edited By: Tyler Hasenpflug CET



Conway, A., Douglas, C., & Sutherland, J. (2015, July 14). Capnography monitoring during procedural sedation and Analgesia: A systematic review protocol. Systematic reviews. Retrieved May 2, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4499911/

Kacmarek, R. M., Stoller, J. K., Heuer, A. J., & Egan, D. F. (2013). Egan’s Fundamentals of Respiratory Care. Elsevier/Mosby.

Leeuwenburg, P. by T. (2013, November 30). So much hot gas – ETCO2 for non-anaesthetists. KI Doc. Retrieved May 2, 2022, from https://kidocs.org/2013/11/much-hot-gas-etco2-non-anaesthetists/

MD, B. S. K. (n.d.). Why capnography. Capnography. Retrieved May 2, 2022, from http://www.capnography.com/capnography-introduction/why-capnography