Capnography and Intubation

Note: I am double posting this on this blog and my capnography blog.

When I was at a conference this past year one of the speakers said the data on prehospital intubation is so bad that if EMS had to go before the FDA to get approval to allow medics to intubate, it would be denied. Based on those studies, which include the LA pediatric intubation study, as well as many RSI studies, I can understand why.

However, those studies (to my knowledge) did not incorporporate continuous wave form capnography.

I believe continuous wave form capnography will eliminate all unrecognized misplaced tubes.

Capnography will prevent hyperventilation in head injured patients and critically injured patients(which may be the reason the RSI studies have poor results — by letting medics intubate patients, RSI puts them at increased risk for hyperventiulation which is much easier to do with an patent airway and an ambu bag just begging to be squeezed.

And capnography can aid in the placement of difficult intubations. It can help prevent multiple attempts and even momentarily delayed recognition of misplaced tubes — all of which cost the patient critical time without effective oxygenation and ventilation.

I believe continuous wave-form capnography will be the savior of prehospital intubation.

***

When many of us were taught to intubate the golden rule was:

NEVER PASS THE TUBE UNLESS YOU VISUALIZE IT PASSING THROUGH THE CHORDS.

The only ways we had to verify our tubes back then were this mantra, listening to lungs sounds and absence of belly sounds, looking for chest rise and mist in the tube — all methods that cannot be considered fully reliable. My safety net was a partner who always held crick pressure for me and could tell me if I was in when he felt the tube pass under his fingers. That was my most reliable confirmation, but we didn’t work together every shift so it was only part-time reliability. We didn’t have the bulb syringe then or colorimetric capnography much less continuous wave-form capnography.

While we all tried to live the mantra of never passing the tube unless we saw it pass through the chords, not all our tubes were in. Hopefully we recognized them right away – either by not hearing lung sounds or having warm gastric contents come flying up the tube to tell us we weren’t where we were supposed to be. How many times did we legitimately think we had passed the tube through the chords and how many times had we hoped we were through? Does the phrase “I think I’m in” sound familiar? particuarly coming from precepting or student medics?

As was proven in a recent study (see below), capnography has the ability to reduce misplaced ET tubes to zero if used. Instead of answering “You think! Pull it out!” or “You’re better hope you’re in – My license and mortgage and food in my babies mouths are riding on it!” Now capnography will tell you. He thinks right or he thinks wrong.

What I am going to suggest now is controversial. It stems from an interesting discussion I had with an articulate commenter on the November log. I suggest that with capnography’s ability to so quickly confirm or disprove a tube that it might no longer be a sin to pass the tube if you are not sure – particularly in the context of the difficult airway. If it wasn’t difficult we would easily see the chords, right? Now I’ll admit to shoving a tube or two in in my time. When you’re looking down the bloody throat of a gunshot or highway crash victim and you can’t tell what you are looking at or when puke and vomit are rising like a biblical Mississippi flood, sometimes you just put it where you think you see air bubbles or where anatomy wise the chords should be. When your own body is crooked trying to get an airway into the man wedged behind the toilet, sometime the view isn’t the best. Ever tried an ice pick style tube?

In people whose chords are hard to see and who are difficult to bag, maybe the best thing to do is just shove the tube in to the best of your ability. And now with capnography, you’ll know you’re in or out almost instantly. Blind tubes are not after all that unusual in EMS. I have done digital intubations, intubations with a bougie and nasal intubations. All blind. I did them that way because that was the only way to get the tube. (Sometimes with IVs on people in extremis, you take a blind shot based on anatomy.) I say if you only have a partial view of the chords or the chords get obscured when you try to pass the tube, go for it if you think you can get it – as long as you have capnography to immediately check the tube.

***

Now here’s a tip. I haven’t done it yet in the field (it only occured to me the other day), but I think I will try it the next time I have to intubate a breathing patient. I have tested the concept and believe it will work.

Before you intubate, attach the capnography filter to the end of the ET tube, insert the stylet – it will fit as long as it is the thin kind, hook up the capnography to the machine, turn it on, and then go in for the tube. If your partner knows how to read wave forms he should be able to tell you if you are in or not when you ask. Either that or listen to the apnea alarm or the lack of an alarm. Make certain you have at least four good wave forms, and then pull the stylet and proceed with your routine checks.

For apneic patients you just have to have your partner ready to attach the ambu bag when you ask. No more looking around for the capnography filter — it is already in place. Keep in mind as always for pulseless patients you may need a little CPR to get your wave form reading. And of course, you’ll need to pull the stylet before you bag the patient.

Make certain you have an extra capnography filter available as backup because if by chance you miss your tube abd gastric contents come up, they will contaminate your filter in addition to your tube.

This method of attaching the capnography filter to the ET tube before intubating also works for nasal tubes. Watch the wave forms as you advance the tube while listening for respirations Once you think you are deep enough and then cough gag and you push through, verify with the wave forms. Just make certain you are not still in the hypopharanx.

Don’t misunderstand me. I still believe you should strive for the gold standard of watching the tube pass through the chords. Don’t make capnography your crutch, but in a difficult airway, it may be your new best friend.

***

Misplaced Tubes

The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system.

Silvestri S, Ralls GA, Krauss B, Thundiyil J, Rothrock SG, Senn A, Carter E, Falk J. Annals of Emergency Medicine, May 2005, pgs 497-503l

If there ever was an argument for requiring continuous ETCO2 monitoring on all intubations, this is it. Over a ten month period, in 11 counties in Florida there were 153 intubations. 93 (61
%)
used continuous ETCO2 Monitoring. 60 (39%) did not. Upon arrival at the Emergency department there were 14 (9%) unrecognized misplaced intubations. There were 0 (0%) misplaced tubes in the group that used continuous ETCO2 monitoring. There were 14 (23%) in unmonitored group.

The authors wrote: “The unobserved unrecognized misplaced intubation risk difference is compelling. This study demonstrates that it is possible to attain a zero unrecognized misplaced intubation rate.”

Four years earlier, another study was done in Florida that showed during an 8 month period out of 108 “intubated” patients brought to a large Florida ED, there were 27 misplaced tubes (27%) on arrival at ED. 18 were in the esophagus, 9 in hypopharanx. 17 of 18 esophageal intubations had an absence of expired CO2, the one with CO2 was nasally intubated and breathing their own. 4 of 9 hyphopharengal intubations had an absence of expired CO2. – Katz SH, Falk JL, Misplaced endotracheal tubes by paramedics in an urban emergency medical services system, Annals of Emergency Medicine, January 2001

The authors wrote: “The incidence of out-of-hospital, unrecognized, misplaced endotracheal tubes in our community is excessively high and may be reflective of the incidence occuring in other communities…Functionally, whether the tubes were misplaced initially or dislodged en route to the hospital makes little difference to the patient….Despite written protocols requiring the out-of-hospital use of ETCO2 devices in our community, we…found their use to be sporadic… We believe that routine use of this technique, both at the time of intubation and as an ongoing monitor during transport, could potentially eliminate the problem of unrecognized misplaced ETT placement….”

Bottom Line: Intubated patients should all have continuous ETCO2 monitoring.

7 Comments

  • Anonymous says:

    The idea of using the capnography to aid with intubation isn’t neceassarily new. I think it’s just one of those lesser known, and lesser used tricks that doesn’t get much attention. I was taught this trick while I took a difficult airway class. I haven’t had the chance to use it yet, but I do like the idea. The BAAM whistle is also a useful tool as well that doesn’t get much attention. And that is a tool that isn’t as commonly used. Maybe that’s something that more services should consider as well?

  • scope2776 says:

    Excellent strategy for using the waveform to confirm nasal intubations! I will definitely use this in the field. I think Paramedics in general need to be more open to using capnography, especially for monitoring intubations. With ETCO2 monitoring devices such as capnography there is no excuse for a misplaced tube. (except of course extraordinary circumstances – such as blood, vomit, occlusion, etc.) I also think capnography has much to offer the Paramedic in patient assessment. Have you ever heard about COPD patients with hypoxic drive? Though rare, most ERs handle only a handful a year, capnography can be used to find the COPD patients who have hypoxic drive. If you put the O2 on and the ETCO2 goes up, bingo – hypoxic drive – titrate the 02 to normal CO2 levels. Also take into account severe asthma patients. Pulse ox. can take minutes upon minutes of apnea before they register even a slight dip in percentage. An 85% pulse ox. is equal to a 52% PO2! With capnography on these patients you can see second by second increase in CO2. In that time you can be preparing your next line of drug, or preparing your intubation equipment. With pulse ox. you’re already behind the ball when you realize there’s a problem! Capnography is an amazing assessment tool in the field. Furthermore while speaking to a doctor in my area he said medical directors would be more receptive to increasing protocol for analgesics if Paramedics would use capnography to monitor their patients respiratory drive! Capnography takes only seconds to set up, why not do it?

  • Anonymous says:

    I’m comming into the world of ALS never not knowing wave waveform capnography. My first OR intubations as a student obviously had it and from that first tube nervousness, to the first tube sucess of seeing the waveform I was sold. My home squad has it and PA is now demanding it by a set date for the entire commonwealth. I can’t imagine doing a field tube without it and admire all the work you do on the topic.

  • Anonymous says:

    Just wanted to comment on the thought of hyerventilating the head injured patient. Several services in my area carry portable oxygen powered vents. A great tool, although expensive.

  • Anonymous says:

    Great Post!!! I am a firefighter/paramedic in Orange County, CA and we were part of the LA peds study. The recent FL study confirms what I have been realizing over the past year or so since we have continuous waveform ETCO2. If a tube does get dislodged during pt mov’t, transport, etc, it is immediately evident and the medics can correct the situation. I recently brought this exact concept up with one of the individuals who led the LA peds intubation study and her response was suprising. She said that having a visual waveform on our monitors would not have any difference on the recognition of a dislodged tube. That simply doesn’t make any sense to me and the FL study confirms that. Thank you very much for bringing this study up. I am actively working on getting this study recognized by our medical director. We need peds intubation back in our protocol.

  • Anonymous says:

    Did someone volunteer for a nasal intubation? It looks like it in the photo.

  • PC says:

    Thanks for the comments. I guess we aren’t the first to capnography, but I sure hope everyone who hasn’t gotten on board yet does. It really is phenomanal when it comes to intubation.

    To the LA medic, good luck with getting intubation back. I think as the word on capnography gets to the EDs and all the researchers, it will help. I think we all have a duty now to spread the word not just to the docs but to many of our peers who haven’t yet embraced the technology.

    To scope2776, you are absolutely right about the hypoxic drive and capnography. You can watch it happen and protect against it.

    And yes that is me volunteering for the nasal tube. I did first shorten the tube a bit with my shears.

    Thanks again all,

    PC

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