# Defining Preoxygenation



## Leanne (Jul 13, 2011)

How do you define preoxygenation? I have been told different things from lab assistants at different schools and I am going to email my former and current instructors. 

In my first school in my home state, we were told this for the ET preoxygenation (Fall 2010): 
- It is the same as hyperoxygenation but it is preferable to say preoxygenation so we don't accidentally say hyperventilate. 
- You bag them once every 3 seconds or so during preoxygenation. Rate is 12-20 breaths per minute. (Otherwise it is not preoxygenating and just regular ventilation with high-flow O2)
- You need to preoxygenate for 2 minutes before attempting to place the tube. This was verbalized as 2 minutes would be a pain and unrealistic for NREMT. 

My medic school says this:
- You bag them 5-6 seconds during preoxygenation or 10 breaths/min. The 12-20 is just for children. 
- There is no minimum time for preoxygenating. It could be 4 seconds.
- Hyperoxygenation is the same as hyperventilation

Here are the 2 skill sheets:
Basic ET Skill Sheet: https://www.nremt.org/nremt/downloads/ventilatorymanagementendotracheal.pdf

Medic ET Skill Sheet: https://www.nremt.org/nremt/downloads/Ventilatory_Management_Adult.pdf

One thing is that our book, published 2008, says this: *
Preoxygenate*_
Adequate preoxygenation with a bag-mask device and 100% oxygen is a critical step prior to intubating a patient. You should mildly hyperoxygenate a patient (approximately 24 breaths/min) the apneic or hyperventilating patient for 2 or 3 minutes. _

http://books.google.com/books?id=im...C8Q6AEwBQ#v=onepage&q=hyperoxygenate &f=false (Should be on page 11.54 and this is the 2010 edition according to Google but it is exactly word from word as the 2008 edition)

So how do you define preoxygenate to NREMT standards and NOT real life? What did your training say, when was your training, and what state was your training in?


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## 8jimi8 (Jul 14, 2011)

Texas.

For NREMT I only stated, preoxygenate the patient.


What does it mean?  I was taught that this is the opportunity to do a "nitrogen washout"  replacing 22% FIO2 with as much 100% FIO2 as possible.  I was also taught to place a nasal cannula at 25l/min while preoxygenating.  I don't have any medical literature to back it up, but what my instructors emphasized makes pathophysiological sense to me.


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## bigbaldguy (Jul 14, 2011)

8jimi8 said:


> Texas.
> 
> For NREMT I only stated, preoxygenate the patient.
> 
> ...



Nasal at 25 l/min? Wouldn't it just shoot out of their nose at that rate? Do you put canula on and then bag over it? Sorry prob dumb questions but I'm a basic so speak slowly and use small words when answering


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## bstone (Jul 14, 2011)

I had the same question several years ago. Instructors said it's hyperventilate with a BVM.


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## STXmedic (Jul 14, 2011)

8jimi8 said:


> Texas.
> 
> For NREMT I only stated, preoxygenate the patient.
> 
> ...



I would love to hear the physiology behind that. I've heard of a specific NC device (cant think of it for the life of me) that is intended for such high-flow o2, but I never found out it's uses or the reasoning behind it's use


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## 8jimi8 (Jul 14, 2011)

It's all about the nitrogen washout.  We aren't talking about maintaining SPO2 >= 92%.  We are taking about replacing atmospheric air with 100% 02.  The idea is that with the massive preoxygenation you gain valuable time to desaturation while preparing to, or intubating.

On another corollary, we have high flow 02 nasal cannula tubing in the hospital. I've had pts on 12-14 l/min before... But for this purpose, regular nasal cannula is placed (unless you have high flow tubing) and then. You bag over it.


For your reading pleasures and disbelieving ways!!  

http://www.epmonthly.com/features/current-features/no-desat-/



Oh and it is possible I made up the 25l/min !  But hey as I said earlier, 'makes sense to me...' lol


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## jediwill (Jul 14, 2011)

On our skill sheets for using the combi-tube it told us to insert opa and bag with room air then later put on 100% o2 to pre-ox the patient....then I had a medic instructor tell me to go ahead and put em on 100% o2 from the get go and just skip the room air....make sense or no?


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## Leanne (Jul 14, 2011)

I haven't heard the nasal cannula. Would it be practical in pre-hospital administration though? I know we like to get the ET tube in before we get to  the ambulance so we'd have to hope the engine crew grabbed their airway bag or the volunteers came with their airway bag from their suv. On the ambulance, I don't see why not beyond the whole it'll require another body to do that. 


> On our skill sheets for using the combi-tube it told us to insert opa and bag with room air then later put on 100% o2 to pre-ox the patient....then I had a medic instructor tell me to go ahead and put em on 100% o2 from the get go and just skip the room air....make sense or no?



Not really because our skill sheets have high-flow O2 and the normal bagging rates as a separate critical failure from failure to preoxygenate the patient. Why even bother having it on there and instead let the people tell the partner to assume bagging? The skill sheets do say that you can put them on highflow from the get-go at the top of the skill sheets. 

I know I am over thinking it, but I don't want to have to pay to retake the national registry practicals because one state is lax on preoxygenating the patient. I'm also nervous about having someone who will ask questions for me to define preoxygenate the patient since there are 3 new critical fails at the bottom of every skill station.


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## Leanne (Jul 14, 2011)

I don't see an edit button anymore but I also pulled out my protocols for my fire department and the medical director uses hyper-oxygenate instead of pre-oxygenate for our oral tracheal intubation protocol.


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## Ridryder911 (Jul 14, 2011)

All NREMT skill sheets are based upon the NHTSA or AHA/ECC curriculum or recommendations.

As per _ AHA Professional Airway Management Course Manual_ (pg17) ..._ "ventilations during respiratory arrest *1 every 5-6 seconds using either BVM or Advanced Airway* 10-12 breaths per minute) Ventilations........_ during Cardiac Arrest ....* BVM 2 Ventilations after 30 seconds* *Any Advanced Airway:1 every 6-8 seconds (8-10 breath per minute)"* ........[/i]

What the NREMT has found as even seen here is the lacking of understanding  differentiation of ventilation(s) and respirations.


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## Leanne (Jul 14, 2011)

So ventilation rate does not change during preoxygenation? Because from what I understand is that you increase the bagging rate slightly during preoxygenation. If you are just doing normal bagging and not going to use an advance airway, it stays the normal rate.


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## usalsfyre (Jul 14, 2011)

This is why NR  (and skills testing in general) is heaped up with fail. 

Preoxygenation may take as little as 6 vital capacity breaths with high concentration O2, but ideally should be accomplished without positive pressure. The idea, as jimi says, is to "washout" the 78% concentration of nitrogen that exist in room air with oxygen at the alveolar level. That way gas exchange will continue to occur during the apnea associated with placing an ETT. Done properly, preoxygenation reduces the "hurry" factor and the potential for hypoxic injury. 

The reasoning behind not using positive pressure during this process is to reduce gastric insulation. Hyperventilation for two to five minutes with a BVM sounds like a good way to ensure it and the resultant aspiration risk from passive regurg. 

For NR say whatever gets you past. More importantly be confident in saying it.


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## STXmedic (Jul 14, 2011)

8jimi8 said:


> It's all about the nitrogen washout.  We aren't talking about maintaining SPO2 >= 92%.  We are taking about replacing atmospheric air with 100% 02.  The idea is that with the massive preoxygenation you gain valuable time to desaturation while preparing to, or intubating.
> 
> On another corollary, we have high flow 02 nasal cannula tubing in the hospital. I've had pts on 12-14 l/min before... But for this purpose, regular nasal cannula is placed (unless you have high flow tubing) and then. You bag over it.
> 
> ...



Nice, thanks! This is the device I was thinking of:

http://www.smiths-medical.com/catal...aquinox/aquinox-high-flow-humidification.html

Called the AquinOx


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## Journey (Jul 14, 2011)

usalsfyre said:


> For NR say whatever gets you past.



For testing, this is probably the most important.

However, for real life you assess the needs of each patient for their primary and secondary problems which will influence V/Q mismatching or the intrapulmonary shunting, the venous saturation factors and cardiac output or your ability to maintain an adequate mean arterial pressure for the patient.

There are many factors that determine oxygen consumption which should be considered for preoxygenation. This also includes age which lack of that consideration brought about a big FAIL when EMS providers were studied for pediatric intubation. 



> Hyperventilation for two to five minutes with a BVM


That would depend if you are able to effectively monitor the PaCO2 from a baseline since the above mentioned factors will affect ETCO2. Bagging real fast also may not mean the patient is "hyperventilated". The opposite may be true.



> The reasoning behind not using positive pressure during this process is to reduce gastric insulation.



There are also reasons behind using it such as the complications which occur when a nitrogen washout is done.

This is why hospital EDs and more advanced ambulance transport agencies have a few different preoxygenation methods to best fit the patient and not just assume the same method which may have been tested primarily on healthy lungs will work on all varieties of the ill.  Some may use a true high flow nasal cannula system, some will use the BVM, some will have a NIV system and of course the Jackson Rees is still popular. EPAP within the airways is a consideration.  The time will also vary by patient from a few full tidal breaths to anywhere from 3 to 8 minutes for some critically ill. And for some, adequate preoxygenation to the standard healthy norm may not be possible or anywhere close to it even in the hospital setting with numerous devices and all the available meds to support MAP. 

You will have to adjust your preoxygenation method to what you have available and perfect your abilities especially if it is the BVM. Some fail at the use of this rather simple device which can be complex in application. Some don't understand the factors of oxygenation, ventilation and O2 consumption.  Others focus primarily on one task and forget the supporting factors or the primary/secondary underlying causes.  For the topic of this thread some are trying to come up with one recipe for all and make broad generalizations without much critical thought process being applies and are taking it to be just one "task".  Of course for an exam like the NREMT which is designed to fit all from the lowest denominator on up in EMS, the simplest answer may have to be correct.   If all factors were normal and the patient was in excellent health, preoxygenation would not be much of a concern.


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## Journey (Jul 14, 2011)

PoeticInjustice said:


> Nice, thanks! This is the device I was thinking of:
> 
> http://www.smiths-medical.com/catal...aquinox/aquinox-high-flow-humidification.html
> 
> Called the AquinOx




That is just one brand. There are several out there since they have been used in the hospitals for about 15 years.

Fisher & Paykel and Vapotherm are also popular.


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## usafmedic45 (Jul 14, 2011)

> So ventilation rate does not change during preoxygenation?



It doesn't have to.  The increased concentration of O2 alone will suffice in most circumstance.  You can do nitrogen washout with even a normal respiratory tidal volume which is a lot less than most EMTs give when bagging (there's a reason I say that....let's see if anyone picks up on it).  You honestly don't even have to bag a patient at all if they are moving air to pre-oxygenate them such as in the case where someone is being tubed to protect an airway, etc.  Now in most prehospital situations, you are going to have to bag the patient at least a little but as Journey said...it varies a lot from case to case.


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## Journey (Jul 14, 2011)

usafmedic45 said:


> It doesn't have to.  The increased concentration of O2 alone will suffice in most circumstance.  You can do nitrogen washout with even a normal respiratory tidal volume which is a lot less than most EMTs give when bagging (there's a reason I say that....let's see if anyone picks up on it).  You honestly don't even have to bag a patient at all if they are moving air to pre-oxygenate them such as in the case where someone is being tubed to protect an airway, etc.  Now in most prehospital situations, you are going to have to bag the patient at least a little but as Journey said...it varies a lot from case to case.



This is also still a practice for pneumothorax or pneumocephalus with the use of high flow (which the NRB is not) devices and high FiO2 concentrations.


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## Journey (Jul 14, 2011)

8jimi8 said:


> So HOW are prehospital providers supposed to obtain ventilation perfusion studies when they are trying to preoxygenate for orotracheal intubation?





Again, V/Q scans are primarily to rule out pulmonary emboli. 

Are prehospital providers taught anything about shortness of breath and breath sounds? 

Do they have any clue what constitutes COPD, asthma, possible pneumonia, CHF, cardiogenic shock or just falling blood pressure? 

What about skin color and SpO2 but only as it correlates to the over all presentation? If someone is mottled I am not going to withdraw oxygen therapy regardless of SpO2 and most definitely if they say they are short of breath and yes, intubation will probably be in their future. Blood pressure must be considered.


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## Chimpie (Jul 14, 2011)

Over 30 posts have been removed from this thread.  This is a reminder to keep posts on topic and to Be Polite.  From our rules:



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