EMCrit Wee – ETCO2 with EGA?

Can we monitor ETCO2 with extraglottic airways? The answer is definitive–I don’t know.

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Comments

  1. Minh Le Cong says:

    Hi Scott
    Just read that porcine arrest model study on carotid blood flow and three EGA airway devices, King alt, Combitube and LMA, that Dr Yannaopoulos and others were talking about in the CPR blog post a while ago.
    Interesting results…did seem to indicate worse carotid flow cw with no airway or ETI. Pig airway anatomy is similar but smaller to humans.
    There was a Korean EMS study that came out in March comparing airway management in OHCA outcomes and LMA did worse than BVM or ETI. I thought it was because the LMA can be tricky to place at times but maybe this porcine study indicates a more sinister mechanism..reduced cerebral perfusion? Carotid flow does not equal CPP but the authors made a good point if venous obstruction in the jugulars occurs as well then this may raise ICP too.
    here are the article links
    http://www.sciencedirect.com/science/journal/aip/03009572
    http://circ.ahajournals.org/cgi/content/meeting_abstract/124/21_MeetingAbstracts/A232

    Maybe epinephrine is not the cause of bad neurologic outcome in OHCA! its the EGA!

    • Ben Hoffman says:

      It can’t hurt to use the ETCO2 on the end of an LMA but I am also not sure it will be overly helpful given it is a low pressure seal prone to leak (which in theory ETCO2 can help you detect).

      A large Japanese study that found no difference in survival between OHCA patients who were intubated vs those who had an LMA placed (1).

      This topic is one I’m not really able to quantify my thoughts clearly on so I’ll step to the side and see what others think.

      (1) Kajino K, Iwami T, Kitamura T, Daya M, Ong ME, Nishiuchi T. et al (2011): Comparison of supraglottic airway versus endotracheal intubation for the pre-hospital treatment of out-of-hospital cardiac arrest. Crit Care;15(5)

      • Remember, our ETCO2 devices suck up but a tiny portion of each breath. A leak is no problem unless it is causing sig. effects on the actual ventilation of the lungs.

    • Jimmy D says:

      Hi Minh, it’s Jim! I use the monicker “Jimmy D” to keep google from creating new links on me.

      Any EGA/airway device that improves ventilation ease and seal (over mask ventilation) can ironically worsen neurologic recovery following resuscitation because it will unwittingly allows the rescuers to hyperventilate with impunity. The work of Aufderheide demonstrated this here in Milwaukee. The LMA outperformed the BVM in its ability to ventilate in the Korean study, but the outcome was worse because of hyperventilation? What do you think?

  2. This is merely an anecdote, but KingLT usage is very common in OHCA in North Carolina. Additionally, waveform EtCO2 is common among the high-performing systems. I believe if there were an issue with their combined use or accuracy we would have heard about it (from Wake Co/New Hanover Co/MEDIC in Charlotte). Granted, that doesn’t exactly prove anything :)

  3. Fletch S. says:

    Another reason to carry a bougie, stick it through that EGD, into the trachea and slide your ETT into place.

  4. Regarding the lma neuro issue, I think till research rules out this complication,one might be better off either with the ett or bvm.

  5. Small correction, the comment is not limited to the lma but also to other supraglotyic airways

  6. Jimmy D says:

    OK, let me see if I understand what you’re asking. EtCO2 monitoring with SGA’s during CPR(?) Are you concerned with the accuracy in terms of diagnosing adequacy of CPR/resuscitation techniques? Otherwise, it will work to indicate that you have a patent airway of course. Ongoing EtCO2 will allow you to ensure you are ventilating.

    • the question is: can the termination rule of ETCO2<10 at the 10-20 minute mark and the return of rosc rule (increase >10, stop and check pulse) still be used with EGA.

      • Jimmy D says:

        It should apply if the ventilation is carefully handled–let me explain.

        If the EGA’s are handled within their performance limits, accurate information should be available through EtCO2 monitoring.

        EGA seals are as such: LMA Classic design can handle 20 cm H2O peak pressure, Second generation LMA’s (LMA Supreme, Air-Q) can handle a bit more, perhaps 25 cm H2O reliably, perhaps as much as 30 cm H2O, and the double balloon EGA’s probably are in the same range as the second generation LMA devices.

        If the ventilation is performed in a manner during CPR in which there is not a lot of “conflict” between the rescuer (or machine) performing chest compressions and the rescuer performing ventilation, the seal pressure of the EGA will not be violated to any substantial degree, and accurate EtCO2 should be obtained. Now this is just conjecture here–indeed, it is common sense. Accurate information is obtained when the patency (i.e., seal) of the system is maintained. So the question of how to maintain this patency of EGA seal during CPR is important.

        The EGA is an “advanced” airway, and the AHA guidelines instruct that ventilations are to be delivered at a rate of 6-10 breaths per minute, independent of CPR (while maintaining continuous, uninterrupted chest compressions). Limiting inspiratory flow rates during BVM are challenging but important, and limiting peak airway pressure to less than the estimated (or observed) seal pressure of the EGA is also important. Inspiratory flow rates can be limited using modified BVM’s that automatically limit how fast the rescuer can squeeze the bag, or other technologic solutions may be employed, such as ventilators or Oxylators. Peak airway pressures can be limited by utilizing BVM’s with integral pressure gauges, and mindfully restricting the peak pressure. Alternatively, technologic solutions can more consistently limit these peak pressures.

        How can you know for sure? Intubate the trachea (through the Air-Q for instance) when a critical decision must be made, and compare the EtCO2 value from tracheal tube to EGA (Air-Q in this case).

        Just food for thought.

  7. Scott, thanks for extending on this topic. Great discussion here as well.

    This is a very interesting topic to me. Ever since the last European Resuscitation Council guidelines came out in 2010, we started using EGA (i-gel in our case – not affiliated with them in any way) to perform uninterrupted chest compressions during CPR.

    Guidelines say only this:

    “Once a supraglottic airway device has been inserted, attempt to deliver continuous chest compressions, uninterrupted during ventilation. If excessive gas leakage causes inadequate ventilation of the patient’s lungs, chest compressions will have to be interrupted to enable ventilation (using a CV ratio of 30:2).”

    So far we had good experience using EGA like this – based purely on my observations. People love the device, since it is extremely fast and easy to insert. We do not need to interrupt chest compressions, and we continue going asynchronous – all things we love. However, I noticed two issues.

    First, the problem of timing ventilations. This is really tricky, and I really do not know if this can even be done. So the idea is to squeeze a ventilation in during the release phase of chest compressions. People are all worried about hyperventilating the patient, so they are counting when they should deliver the next ventilation or following an audio or visual prompt (in our case audio from a mobile phone app). They are ready to ventilate and than there is this action going on 120 times a minute on the chest that they should be following. WOW, what now? How do they deliver this ventilation. Slow, over 1 second? But this guy is pumping 2 times a second. Should they inflate quickly or maybe extra slowly? Should they use a lower or higher volume and pressure? What I notice then is that after a while they cannot keep track, and just ventilate as if we had an ET in place.

    Second, if we follow this assumption of timing ventilations, I cannot use my ventilator, which I love to do, especially if I am working in the pre hospital setting with only my team of three. I really have to free some hands. But the ventilator does not recognize phases of the chest compression duty cycle. OK. But is there a difference anyway? Are people trying to time ventilations any better?

  8. Jimmy D says:

    There is a technological solution to the problem of timing ventilations with continuous chest compressions–it’s the Oxylator. With mask, EGA or tracheal tube, it will ventilate on the decompression phase of CPR with a fixed minute ventilation of 10-12 lpm. The Oxylator FR-300 sells for $500 USD here in the states, and there are plenty of European distributors (where it is more popular, by the way). I’ve used the Oxylator in 2 cases of cardiac arrest (one with a Combitube and one with a tracheal tube) and it performed effective ventilations throughout the arrests.

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