# Still oxygenating before intubation in cardiac arrest?



## Mohrenberg (Oct 31, 2011)

A question just popped into my head so I figured i would hop on here and get some feedback on it.
It seems that restricting oxygen is getting more and more popular for cardiac arrest and ROSC patient. Some services around here are going to non-re breathers and not bagging the patient at all during cardiac arrest.

So I was hoping I could get a few people around here that are currently trying out cardio cerebral resuscitation and other new forms of resuscitation if they think the whole pre-oxygenate/hyperventilate before intubation is going to be removed from the intubation sequence.

I enjoy reading these new articles about post cardiac outcome and how restricting oxygen (SAO2 of 94%) and induced hypothermia has made a big impact on the survival rate.
I live and work in a very rural area with a population of 3000 and the nearest hospital 25 minutes away. so we don't get many codes, and we NEVER get to try out the "cutting edge" in EMS care.


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## Shishkabob (Oct 31, 2011)

I'm just going to be honest here,  most patients that need intubation are not going to get adequate pre-oxygenation beforehand, which is why we're going for intubation.  I have not found any studies that backup pre-oxygenation (not saying they don't exist, I just havent found them). 

(Like I said, most, not all.  Clearly there are exception)  





The issue with "pre-oxygenation" is that how most places teach / want it done is to essentially hyperventilate the patient to wash out the nitrogen and get as much oxygen in as you can... clearly, that's the exact opposite of what we want in an arrest with cerebral vasoconstriction.  So to answer your question, yes, I do see "pre-oxygenation" getting tossed out in cardiac arrests.


(Plus, a few of the more progressive places are saying just drop a BIAD off the bat now instead of ETI)


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## lawndartcatcher (Nov 7, 2011)

It's not a matter of "restricting oxygen" to these patients - it's an attempt to not create positive pressure in the thoracic space and prevent the heart from refilling (because at this point it's replying completely on external pressure generated by a police officer or LUCAS). 

Our service is taking part in a pilot program in which, as part of the protocol, we don't perform an advanced airway for the first ~10 minutes of the call. Instead, we (or our first responders) place a NRM and concentrate on compressions.

The thinking behind this is twofold: 

The normal motion of good quality compressions should force some air out while the recoil phase should create a negative pressure, drawing oxygen in. Since diffusion of oxygen across the aveolar membrane is passive all we need to do is ensure that there's a higher percentage of oxygen in the lungs than in the surrounding capillary beds
Studies have shown that, in a patient who was perfusing normally prior to arrest, ABG values for oxygen remain up around 70% at the ten minute mark. So even if their heart stopped beating there's enough oxygen systemically that, as long as we keep blood flowing (via police or other mechanical device) there should be a temporary supply.

Here's the problem with this: When we show up we have no idea how far into that ten minutes we are. If they're a respiratory arrest the above doesn't apply since they were probably starting with a half-empty tank to start with, and even cardiac arrests may not have been perfusing all that well before they keeled over. "Pre-oxygenation" is really a misnomer; you can't supersaturate blood - once all 4 hemoglobin molecules are full, that's it. No saving for the future. What we're really doing is "oxygenation". Depending on your service and protocols that probably means a BVM with 100% oxygen (the NRM is intended to allow for lower intrathoracic pressures which hopefully allow for better filling of the heart between compressions (See "Frank-Starling mechanism"). At the end of the day, though, it's BLS before ALS and waiting to get a tube into someone before you bag them = witholding potentially lifesaving therapy.

BTW, our service is using CCR. Usually our local PD has the patient on a NRM and is performing compressions as we come through the door. Our save rate is up around 50%. National average (CCR and non-CCR) is still around 4%.


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## systemet (Nov 7, 2011)

Great post.

Ventilation has less of an effect on pCO2 intraarrest.  If cardiac output is < 25% of normal, there's only so much CO2 you can remove with overaggressive ventilation.  

Faster ventilatory rates become more of an issue when they (i) disrupt compressions, i.e. before an advanced airway, and (ii) when they decrease venous return through increased intrathoracic pressure.

As lawndartcatcher points out, in most cardiac arrest settings, arterial oxygen content is maintained for a while as there just isn't that much oxygen delivery / consumption going on.  A primary asphyxial arrest is a different matter, of course.


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## RocketMedic (Nov 8, 2011)

What about patients with difficult airways? Does the pressure differential work with them as well or do we need open, clear, "perfect" airways?


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## lawndartcatcher (Nov 9, 2011)

Rocketmedic40 said:


> What about patients with difficult airways? Does the pressure differential work with them as well or do we need open, clear, "perfect" airways?



It's a completely separate issue - if you increase intrathoracic pressure past a certain point you're not allowing the heart to completely refill. Period. Doesn't matter if they're a Mallampati 1 or 4 - the physics in the chest cavity aren't going to change. But if they're not breathing they need oxygen.

If they've got a difficult airway because of something else (facial trauma, excess amounts of pink frothy sputum, etc.) they're already starting with half a tank, so  they'll need a clear airway (suction) and BLS oxygenation immediately (i.e., before you yank out your advanced airway bag.)

Patient presentation and local protocol should dictate *how* your patient receives oxygen, but common sense should tell you that any hypoxic patient - currently alive or pre-dead (we don't have dead people in the back of the ambulance, just the aggressively non-living.) should be receiving oxygen.


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## RocketMedic (Nov 9, 2011)

I understand the intrathoracic pressure issue, but below that threshold, I don't know if a patient with a poor Mallipati score (say, your obese patients, patients suffering from COPD, etc) would get even the *minimal* amount of airflow generated by compression-related pressure changes.


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## SanDiegoEmt7 (Nov 9, 2011)

I agree with forgoing the tube until your drugs are on board.  But as mentioned above a great deal of our codes have been hypoxic to some degree for quite awhile prior to coding.

In my locale, a patent BLS airway (good chest rise) is all thats required during the code.  If time allows, or its a dual medic ambulance, than the ET intubation is still the golden standard.

I understand the idea of reducing intrathoracic pressure and how this benefits Frank Starling's Law, but if you're talking about giving 2 ventilations with a BLS airway, wouldn't the first compression or so negate the air into the lungs and return the thoracic cavity to the pressure maintained during compressions.  

I think one of the basic points of working a code is ensuring that you have a patent airway.  If you simply place a NRB mask on at 15LPM how can you verify that any of that O2 is even getting to the lungs?  The two respirations providing needed oxygen in the first few minutes is debatable, but the first two respirations showing a patent airway every 20 secs at the end of a cycle is important.  

In the military they drop tubes and never bag them.  If supplemental oxygen is being supplied without respiratory support, I would at least like to see a definitive airway in place.


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## Fish (Nov 10, 2011)

Tubes in a pulseless person are becoming the Fossil way, a King-LT or Combitube is all that is needed. If you get pulses back and need to RSI this patient, by all means. Tube!


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## systemet (Nov 10, 2011)

Rocketmedic40 said:


> I understand the intrathoracic pressure issue, but below that threshold, I don't know if a patient with a poor Mallipati score (say, your obese patients, patients suffering from COPD, etc) would get even the *minimal* amount of airflow generated by compression-related pressure changes.



Difficult airway =/= obstructed airway.  There are plenty of Mallampati Grade IV airways walking around breathing just fine right now.  These are people where direct laryngoscopy is predicted as being difficult, not people who have a resistance to inhalation / exhalation. Exhalation under resting conditions is a passive process, even in the grade IV airway.

Now where this idea of passive air exchange is going to be an issue is if the patient has an anatomic airway obstruction, or a FBAO, laryngedema, or bronchospasm, etc.  And in an asphyxial arrest, ventilation is probably a lot more important than in the average run of the mill witnessed arrhythmic code.  But even here, exchanging oxygen across the lungs and blowing off CO2 is going to ultimately be limited by a lack of delivery of CO2-rich venous blood to the right heart, and (hopefully) oxygen-rich arterial blood to the systemic circulation.


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## systemet (Nov 10, 2011)

SanDiegoEmt7 said:


> In my locale, a patent BLS airway (good chest rise) is all thats required during the code.  If time allows, or its a dual medic ambulance, than the ET intubation is still the golden standard.
> 
> 
> 
> ...


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## lawndartcatcher (Nov 10, 2011)

Systemet - Two great posts with some excellent points. Especially about the Mallampati scales. Mallampati isn't "How cruddy is their airway?" but rather "How much of a pain in the *** is this going to be?"

So I think we're exploring a couple of separate (yet related) issues here:

Is there a purpose in providing a BLS airway prior to intubation?
Is there a correlation between anatomic difficulty in intubation vs airway patentcy?
What are some of the issues with traditional methods of oxygenation?

1) I think the general consensus is "Yes. Of course we want to oxygenate any patient who needs it. Particularly the dead ones."

2) No. Common sense (and a quick observational trip to the Wal-Mart) tells us exactly what systemet said: folks who are traditionally difficult to intubate (the Mallampati IVs) - like baby Huey and his wife who are tucking into their third plate of nachos - can walk around and breathe perfectly well. 

2a) That being said, it's up to us  as *clinicians* to try and figure out why the 300 pounder is in cardiac arrest. (Okay, *specifically* why they're in arrest *today*. Big picture-wise, I'd bet on the morbid obesity / sedentary lifestyle / 2-pack-a-day smoking habit / noncompliance with diabetic meds) If it's an airway issue that's addressed somewhat differently than a purely cardiac issue.

3) I, too, will be really interested to see what comes from some of the current research, but I'll tell you anecdotally that the CCR study we're taking part in is yielding some impressive numbers. The services that are taking part in it are seeing "waddle out of the hospital" numbers between 40% and 50%. The study protocol has us (or our first responders) placing a NRM and a Lucas on the patient at the start of the code and we don't even think about intubation until ~10 minutes in. The argument is that a) good quality compressions should create enough of a pressure differential throughout the thoracic cavity to push a small amount of CO2 out while drawing O2 in and b) oxygen will diffuse down the airway on its own (since it's a passive process). 

3a) Are there benefits to intubating someone who's unable to protect their own airway? Absolutely. Should it always be the first thing we think of? Of course not. I'm intrigued about the idea of a passive ET tube - the doctor who's overseeing this study mentioned that as well. It would seem to give the benefit of protecting the airway without increasing intrathoracic pressure. I wonder if some brilliant shade tree mechanic / medic could come up with a non-positive-pressure (or limited positive-pressure) device that could deliver 15 lpm down an ET tube. When you invent it pm me and I'll give you an address to send my royalty check to...

It's cool stuff - the last 5 years or so have definitely turned a lot of what we thought we knew on its head.


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## BLS Systems Limited (Nov 10, 2011)

*Oxygen delivery in Apneic Patients*

_"I wonder if some brilliant shade tree mechanic / medic could come up with a non-positive-pressure (or limited positive-pressure) device that could deliver 15 lpm down an ET tube."_

As an RT who has performed several tests for apnea/brain death, the standard was to deliver oxygen at 10 LPM via a suction catheter placed down the ETT, just above the carina, thumb port taped.  The test involves starting with normal ABG's, removal from the ventilator and placement of the suction catheter.  Regular gases are taken, watching for increases in pCO2.  PO2 levels should not decrease during this time.  A rise of pCO2 over a prescribed period of time indicates apnea. Obviously, any visible chest rise during the test would negate the ABG results.

Is this something you were looking for?


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## SanDiegoEmt7 (Nov 10, 2011)

> I also worry that by removing one of the most common reasons for performing ETI, we're detraining a lot of paramedics who get limited opportunities to intubate. This is not going to help success rates for some RSI programs.



This is very true, without successful tube numbers it would be very hard for anyone to argue their medics are ready to RSI patients.

I also would like to note that blind placed adjuncts like the king and combitube are much more than simply putting a NRB on a patient, but seem like a viable alternative.  If the military approach was taken, drop the king airway and just do compressions only, no ventilations.

Either way, I think that hypothermic studies are what interest me the most since in all these scenarios we are all basically agreeing that the compressions are minimally successful and acidosis and cell death are major enemies.


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## RocketMedic (Nov 10, 2011)

The military is de-emphasizing the King and Combitube due to overuse and medics forcing it to fit outsized/wrongsized patients.

I still think the ET is the gold standard and belongs in many of our codes, but I think that the cornerstone of our cardiac-arrest therapy should still be compressions and electricity absent an airway blockage or asphyxiation-related arrest.


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## icefog (Nov 26, 2011)

Yup, "pre-oxygenation" may be a poorly chosen term, but the idea behind this was not to increase the amount of oxygen per Hb molecule, but rather to fill up the lungs with as much O2 as possible (including the residual volume), that is to say replace/enrich the air already found in the lungs (which contained a lower O2-concentration). In light of what lawndartcatcher said, I don't know how valid this point remains, in terms of actual benefits.

Our service doesn't use any kind of mask ventilation, it's just the last backup - but intubation is generally discouraged, too. What we do is, one of us starts compressions and the other gets the King in, and then it's onwards as usual. Once started, compressions are never interrupted, except every 2 minutes for the rhythm check.

We haven't had relevant size mismatch or aspiration problems with the LTs, and ventilation during compressions works out great.


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## Doczilla (Dec 4, 2011)

One of the biggest reasons CCR and CPR are so drastically different boils down to CPP [coronary perfusion pressure]. It's not really about preoxygenation, or "to tube or not to tube."

Anyone ever hear back in 2004 that they were doing compression-only CPR in Japan? We all thought it was crazy, until we looked at the research. CPP is a reflection of the net pressure in your coronary arteries, as the name implies. The normal CPP in any given adult is approximately 25-30mmhg. 

Remember, that the function of the coronaries is to feed the heart first, and in cardiac arrest this is of paramount importance if ROSC is to be achieved. They determined through several studies that you need to produce at least 15-25mmhg to reach ROSC in most cases. Studies showed that CPP during BLS [30:2 CPR] up to 2005 was on average, between 1-7. 

If you add a full blown ACLS resuscitation to it, you'll reach about 15mmhg, thanks to the vasoconstrictors, and uninterrupted chest compressions. 

The problem with old-school BLS was that every time you stopped compressions to give rescue breaths, your CPP would fall from a 7 [best case scenario] back down to zero, and that the 30 compressions being done was not enough to restore this [unsatisfactory] number. 

With the understanding that most adults have a residual capacity for about 5-7 mins of oxygenated blood [when apneic], the concept of uninterrupted chest compressions seems desirable not only from a clinical concept of maintaining CPP, but from the layperson not wanting to perform "CPR" for fear of catching a disease. Plus, most cardiac arrests puke. Who wants to put their mouth on that?

Maintaining CPP is more important early on than maintaining "good" pao2 in cardiac arrest. The residual o2 in the blood and lungs will be sufficient for at least a few mins, until ALS or an AED arrive. 

So this brings us to preoxygenating cardiac arrests: It's not really needed if they were viable [<2-8 mins down] to begin with. ALS codes are ran with everything being done simultaneously thanks to greater capability and/or manpower.

 And like it was mentioned before, the King LTD seems fine when you need to load and go, unless you NEED that extra drug route. [The introduction of the Easy I.O a few years ago is minimizing that.] 

Just my .02.

V/R, 

John


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## BigBad (Dec 4, 2011)

The word "hyperventilate" is no where to be found in my protocols.   I preoxygenate while I get my equipment ready.


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## MedicPatriot (Dec 18, 2011)

Fish said:


> Tubes in a pulseless person are becoming the Fossil way, a King-LT or Combitube is all that is needed. If you get pulses back and need to RSI this patient, by all means. Tube!



Whatever happened to the ol' skills drill? I joke, partly. If the BVM is working fine I say just bag them but two things come to mind. If its a shockable arrest then screw the tube you need to convert the rhythm first. If its asystole well sure do BLS before ALS but when its been a while into the code you may as well intubate before you call it.


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