Face Mask Capnography for procedural sedation – tip thanks to Minh Le Cong

Here’s a great tip for utilising standard EtCO2 monitoring equipment during procedural sedation, thanks to Minh Le Cong (@rfdsdoc)

Why is this important or useful? Because apnoea (as evidenced by loss of EtCO2 trace) is when you lose your protective airway reflexes during procedural sedation (which is when your aspiration risk starts going up), and in a patient with supplemental oxygen applied can give you advanced warning that the patient is about to start desaturating, so you can take remedial action (eg: cease the administration of sedative, apply some stimuli to get the patient to take a breath, and possibly use a reversal agent if needed). It’s also useful to help pickup complications such as laryngospasm, particularly – as Minh points out below – in noisy retrieval vehicles.

Here’s some extra info from Minh on the technique:
We tested the setup using increasing oxygen flow rates through the hudson mask. We only found appreciable waveform degradation above 10L/min . The EtCO2 reading is of course not reliable but it still gives you a trend. The main use I find having the capnography for is in the noisy aircraft, its hard to hear someone going into laryngospasm and they can look like their chest wall is rising up and down but actually be moving no air. Sooner you realise there is a problem you can intervene before hypoxia sets in.

This is a great technique that we’d strongly encourage anyone doing procedural sedation without capnography to start using.

Another improvised capnography setup – if you have sidestream capnography – involves the use of:
(click on phtos to enlarge)
A mixing cannula (the plastic cannula the nurses use to draw up liquid medication)


2) An oxygen mask with the small exhalation holes on the side


3) Sidestream capnograph tubing.

Basically you pull the green connector (the “syringe end”) off the mixing cannula, they come off quite easily:

And plug the small end into one of the small holes on the side of the oxygen mask:

and then just connect the the EtCO2 tubing to the green connector! Easy.

Needs to be closely watched for dislodgment, and remember, another reason for loss of CO2 trace is blockage of the tubing by condensation, or kinking of the tube.

Surprisingly use of EtCO2 monitoring is not routinely receommended by either ACEM (no policy/guideline on procedural sedation) or ANZCA, merely that there should be “access to it”. Personally I’ll be using it from now on!

4/2/12: Update
Another tip from Ed Burns (ED Reg, catch him on Twitter @edjamesburns)

Simply snip the connector end off the sidestream EtCO2 tubing and slide it through the little hole.

Alternatively I reckon you could just slide it under the side of the oxygen mask. Likely to still work as long as it’s near the patients mouth/nose.

Would a simple 14/16G IV cannula work as well I wonder? Will have to test it out when I’m back at work.

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