You’ve finally decided on a monitor. Now it’s time to decide on the method you will use to sample the CO2.
The first thing to consider when choosing the type of sampling line or “sampling” cannula for monitoring CO2 is the type of monitor that you have. Does it require a male or female luer on the monitor side of the sampling line or cannula.
The next consideration would be the patient side of the equation. With that comes the question:
Do you deliver supplemental oxygen and how? Through an oxygen cannula or with a nitrous hood?
1. We occasionally deliver supplemental oxygen, but not always.
One effective way of monitoring CO2 in a non intubated patient, is through a nasal sampling cannula.
It is a specific “sampling cannula” designed for CO2 monitoring. It is not your standard 50 cent oxygen cannula….more like a $4 cannula. With this sampling cannula you will sample CO2 through both nostrils. Therefore the CO2 value will be more stable as you are obtaining a greater amount of data with no additional gases being introduced other than room air.
Now, when you are ready to deliver supplemental oxygen you can set the nitrous hood on top of the sampling cannula or you could “piggyback” your oxygen cannula on top of the sampling cannula. Obviously this can be a cumbersome method, but it is doeable. This would be considered a “stacked” or “piggyback” method of monitoring CO2.
2. We deliver supplemental oxygen through a cannula.
There are specifically designed cannulas just for this purpose. Each manufacturer has a slight variation in their design, as you can see from the diagram below.
A recent study at the Medical College of Wisconsin shows that a “divided” cannula, such as, the one manufactured by Salter Labs is the only one that shows efficacy with respect to BOTH O2 delivery and CO2 measurement. Some are more effective at delivering oxygen and others more effective at monitoring CO2.
3. We use a nitrous hood to deliver oxygen.
Lastly, if you use a nitrous hood to deliver your supplemental oxygen, you have a couple of options.
2. Use a disposable custom designed nitrous hood and connect to it using a straight sampling line. Here’s an example of one by Accutron:
This should clear things up for you a bit. If you have questions, don’t hesitate to ask.