In my post of yesterday, I wrote the following:
While my preceptee prepared the tube, and our crew did CPR, as an experiment I applied a nasal capnography cannula to the patient to see how well we were ventilating with just CPR and bagging. I have heard it suggested that this is an excellent way to assess ventilation in cardiac arrest and or the need for intubation or the ability to delay it while concentrating on compressions or drug administration. The ETCO2 didn't even register, which was either due to poor bagging technique or just the plain difficulty of effectively ventilating someone in arrest by bagging. I would like to try this experiment again on a patient when we have more hands to help and a better seal with proper head positioning.
Later in the day we did a call to the local university hospital where while my preceptee wrote up the paperwork, I went down to the medical library to get copies of some articles from the latest issue of Prehospital Emergency Care, which comes out quarterly. The Jan-March issue features a section of "Abstracts for the 2008 NAEMSP Scientific Assembly," which includes almost 100 prehospital research abstracts. I was interested to find one titled "The use of End-tidal Carbon Dioxide Values Obtained During Bag-Valve-Mask Ventilation to Predict Post-Intubation Values."
Their conclusion "ETCO2 values obtained during BVM appear to accurately predict values following intubation. This is potentially useful to establish a baseline to improve the reliability of capnometry for ET confirmation and may allow for guidance of CPR and determination of futility...We believe ETCO2 sensors should be applied during BVM rather than waiting until after intubation."
The study was conducted in San Diego and involved over 221 patients, including 90% in cardiac arrest.
I will definitely try this experiment again.
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Note: In a comment New Medic suggests there is an adaptor that connects the sensor to the bag mask -- that the nasal cannuala is not used in this study. This makes more sense now as to why we had no reading at all. I will post more on further investigation.
