Even the dead exhale CO2

October 9, 2013 by  
Filed under All Updates, Fascinomata, Resus

cadaverETCO2iconCardiac arrest patients sometimes have unrecognised oesophageal intubations because clinicians omit capnography, based on the assumption that circulatory arrest leads to an absence of exhaled CO2. This is wrong, and reassuringly the latest ILCOR cardiac arrest guidelines recommend waveform capnography during resuscitation.

Of interest is the fact that even corpses have CO2 in their lungs. While not clinically relevant, this may have value when fresh frozen cadavers are used for airway training, since we might be able to supplement the realism of airway instrumentation with the realism of connecting the capnography adaptor and circuit and seeing confirmation on the monitor.

This preliminary study, completed by my Sydney HEMS colleagues, needs further work, but it’s an interesting area.

Sustained life-like waveform capnography after human cadaveric tracheal intubation
Emerg Med J doi:10.1136/emermed-2013-203105


Introduction Fresh frozen cadavers are effective training models for airway management. We hypothesised that residual carbon dioxide (CO2) in cadaveric lung would be detectable using standard clinical monitoring systems, facilitating detection of tracheal tube placement and further enhancing the fidelity of clinical simulation using a cadaveric model.

Methods The tracheas of two fresh frozen unembalmed cadavers were intubated via direct laryngoscopy. Each tracheal tube was connected to a self-inflating bag and a sidestream CO2 detector. The capnograph display was observed and recorded in high-definition video. The cadavers were hand-ventilated with room air until the capnometer reached zero or the waveform approached baseline.

Results A clear capnographic waveform was produced in both cadavers on the first postintubation expiration, simulating the appearances found in the clinical setting. In cadaver one, a consistent capnographic waveform was produced lasting over 100 s. Maximal end-tidal CO2 was 8.5 kPa (65 mm Hg). In cadaver two, a consistent capnographic waveform was produced lasting over 50 s. Maximal end-tidal CO2 was 5.9 kPa (45 mm Hg).

Conclusions We believe this to be the first work to describe and quantify detectable end-tidal capnography in human cadavers. We have demonstrated that tracheal intubation of fresh frozen cadavers can be confirmed by life-like waveform capnography. This requires further validation in a larger sample size.

Comments

2 Responses to “Even the dead exhale CO2”

  1. Christopher on October 10th, 2013 03:38

    I assume this is due to some sort of ongoing off-gassing postmortem?

    (When working arrests where the ETCO2 is approaching 0, I’ve asked that ventilations be slowed to once or twice a minute to rule out hyperventilation. Which leads to the follow-on: if you’ve hyperventilating your cardiac arrests you may be stopping the resus too early due to iatrogenic hypocarbia.)

  2. cadaveric capnography? | DAILYEM on October 11th, 2013 23:01

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