SOCMOB How To: Make Your Own End-Tidal CO2 Detector


The ASA now recommends that all procedural sedations (not conscious sedations!) be done with quantitative waveform capnography. While I understand it’s not feasible in some places, capnography is a hugely valuable tool, and detects apnea long before the pulse ox reading drops.

Where I work, there are no fancy nasal prongs or face masks with built in CO2 detectors, so in order to get a capnograph, some improvisation is needed.

An anesthesia resident helped me with this idea, as did Minh Le Cong’s great 4 minute video on MacGyvering an End-tidal CO2 detector on the SMACC website (link below).  Thanks to both Kyle Raab and Minh for the idea.   After posting this initially, Jeremy Field made the simple but brilliant suggestion of just cutting off the ETT adapter part of the ETCO2 detector to improve the design.   So, I’ve made a new video showing this and replaced the old one.

For all the Saskatchewan docs and other ED people out there, this video shows you how to make a Microstream Sidestream ETCO2 detector work with your nasal prongs, face mask or non-rebreather device.  I receive no payment from, nor do I have any affiliation with this product, it’s simply what is available in our ED.

Over the next while I’ll be releasing more “SOCMOB How To” videos.  Click here to go straight to YouTube video or if it isn’t working below.  Enjoy!

If you enjoyed this video, like it, tweet it, etc. and spread the #FOAMed.  If you didn’t like it, send me suggestions on how to improve.

Here are the links for Minh Le Cong’s video, as well as his great PHARM (Pre Hospital and Retrieval Medicine) website/podcast.

In other news, SOCMOB has joined forces with BoringEM, ERmentor and Want2BeMD in a University of Saskatchewan FOAM collaborative.  Check out all of their great FOAM here.


Chris Bond



  1. Jeremy Field says

    Why not cut the ETT adaptor off and insert the sidestream tubing directly into a hole in the Hudson mask? This would be much less bulky, and also save the cost of opening an ETT. In addition, using your setup with a non-rebreather mask would significantly reduce the inspired oxygen fraction by providing a low resistance inspiratory pathway for room air. MLC repurposed a mainstream analyser and so did not have this flexibility.

    • says


      Great suggestion, thanks. It makes complete sense and you’re right, saves on bulkiness and the ETT adapter. I’ll try it out today. If it works and still gives a good reading, I’ll revise the video.



  2. says

    Great stuff from SOCMOB crew

    There’s an evolving series of ‘how to do it’ vids over at ’50 shades of brown’ on the ki-docs website (for what to do when sh** hits the fan)…aimed at rural docs, but may be useful to the ED juniors

    You are more than welcome to use those videos too, available via as FOAMed

    …or shoot me an idea if you want me to video a concept/how to do it clip

  3. Minh Le Cong says

    hey Chris, Jeremy
    great stuff, well done. IN my service we dont have sidestream CO2 sensors , just the mainstream. You would be surprised but I have not had one patient complain about the discomfort of the sensor pushed through the side port of the mask..but then again they are usually on a ketamine drip :-)

    One issue with just sticking the side stream tubing in via a side vent hole in a mask is how to secure it as it will easily fall out. You can tape it into the inside of the mask but that is still not very secure. What you demonstrated first Chris in this video is fine and holds the sensor in the mask snugly. Dont even bother using the ETT adapter..we dont!
    If its for PSA, whatever you are giving them will alleviate any discomfort from that sensor!

    great work once again!

    • says

      Thanks Minh and Tim. I tried out Jeremy’s suggestion to just cut off the top of the Microstream device and it works great. I find the ETCO2 readings are actually even higher this way. As a bonus, you can easily use it with nasal prongs as well, by just snipping the cannula below one nasal prong and putting the CO2 wire through.
      I’ll be replacing the original video with one showing Jeremy’s revisions.

      Tim, thanks for the site. Glad to see you both enjoyed SMACC. I’m jealous.


  4. David Lendrum says


    I tried out your end-tidal McGuyver idea and it worked great. Thanks for the video. I was a bit skeptical if it would work well if the oxygen flow was really high. I first used your NP and the end-tidal sensor stuck in the small cut place in it with the oxygen cranked and it worked well. I think put a NRB face mask of oxygen overtop and cranked that too. The high flow rates did bring the end-tidal down by about 1 point, but the data it was giving back was most definitely still reliable.

    Thanks for sharing!


    • says

      Hey Dave,

      Is this FMC Dave Lendrum? If so, I’ll see you back in Calgary next year.

      Glad you enjoyed the idea. When you say one point lower, what kind of ETCO2 numbers were you getting with the prongs/mask combo at high O2 flows?

      Thanks for reading.


  5. says

    Dear Colleagues:

    Because you’ve been discussing end-tidal CO2, I thought this might interest you.

    I have developed an iPad app for teaching the factors that affect the composition of “Alveolar Gas”. This app for the iPad is based on my computer program by the same name that’s in the American Physiological Society’s peer-reviewed archive of free teaching materials. A student or instructor can manipulate variables like tidal volume, dead space, and the oxygen consumption rate and see how they affect alveolar PO2 and PCO2. The computer program is free; it and several others that I have submitted can be downloaded here:

    The iPad app is suitable for use either as a classroom demonstration or self-instruction. It’s available in Apple’s App Store:
    An iPhone version is not available at this time.

    Is there a way to make this information available to your students and colleagues? Thanks for your help.

    Best regards,

    A.P. (Pete) Shepherd, Ph.D.
    Professor (retired)
    University of Texas Health Science Center at San Antonio


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