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Apneic oxygenation: Everything you know is wrong
Take your time to get that tube smoothly, non-traumatically into trachea on 1st pass
By Kelly Grayson
It was during paramedic class, oh so many years ago, when I first heard it: "If you can't get the tube within 30 seconds, stop the attempt and ventilate for a while."
My instructors paraphrased it in more practical terms, admonishing us to hold our breaths when we began an intubation attempt. "When you need to take a breath, so does the patient," they reminded us.
The concept was reinforced during countless NREMT skill stations, where we routinely failed candidates for taking longer than 30 seconds on a single intubation attempt. Those poor candidates trudged the walk of shame back to the routing area to take their places beside the other failed candidates who committed the unpardonable sin of forgetting to say, "I'll have my professional partner hyperventilate the patient while I prepare my equipment."
I was also taught that a nasal cannula can only deliver a maximum of 44 percent oxygen and that non-rebreather masks can provide more than 95 percent oxygen.
Turns out, none of the above was true.
Back then, my instructors didn't spend much time dwelling on concentration gradients and the oxyhemoglobin dissociation curve. It wasn't until years later that I learned that hyperventilation is a bad thing and that an adequately preoxygenated patient takes quite some time to desaturate. If your patient is adequately preoxygenated, you're far more likely to do harm by rushing an intubation attempt to get it done in less than 30 seconds than you are likely to cause a hypoxic state.
In other words, you can afford to take your time.
Current recommendations for preoxygenation prior to ETI are to give at least eight full tidal volume ventilations of 100 percent oxygen via BVM or to apply a non-rebreather mask at 15 lpm for four minutes. That non-rebreather mask, of course, also requires that you maintain adequate airway positioning during that time.
Keep the patient's head elevated so that the external auditory meatus is aligned with the sternal notch. Their facial plane should be parallel with the ceiling and not tilted back.
Preoxygenated with those methods, a healthy adult will take as much as eight minutes to desaturate to a spO2 of less than 90 percent. After that, it gets ugly fast. But even cutting that figure in half for the obese or those with chronic pulmonary pathology, you still have minutes to secure a tube, not seconds.
Still, there's a way to maintain adequate oxygenation during an ETI attempt: Apneic oxygenation using a nasal cannula, an idea espoused by Dr. Richard Levitan, airway management guru and Associate Professor of Emergency Medicine at Jefferson Medical College. As Dr. Levitan explained it in Emergency Physicians Monthly:
While the common perception is that a non-rebreather mask is the pinnacle of oxygen administration, effective FiO2 from these masks may not create optimal pre-oxygenation at flow rates of 15 lpm. This is because the measured inspired oxygen in the hypopharynx with a non-rebreather at 15 lpm is only 60-70%. The reason for this is the patients expired gases are mixing with the applied oxygen, and also because expired gases accumulate in the nasopharynx. Quiet breathing involves flow rates as high as 30 lpm; maximal pre-oxygenation with a loose-fitting non-rebreather may require a flow rate as high as 48 lpm. High flow nasal oxygen has been shown to flush the nasopharynx with oxygen, and then when patients inspire they inhale a higher percentage of inspired oxygen.
To use Dr. Levitan's procedure, simply add a nasal cannula at 15 lpm to your preoxygenation with BVM or non-rebreather mask, and keep it running until you secure a tube and resume ventilation. The nasal cannula will allow you to reach oxygen delivery levels unobtainable with the BVM or non-rebreather alone, and it will provide a pressure gradient that will keep the alveolar capillaries suffused with oxygen for as long as you'll need to secure an airway. In studies, researchers were able to maintain apneic patients' oxygen saturation at 98 percent for up to 100 minutes.
The only drawback is that it requires a second oxygen source, and yes, CO2 buildup is still a concern, but one that can easily be reversed once you've secured a means to ventilate the patient effectively.
Try this in your clinical practice, and buy yourself and your patients some extra time to get that tube smoothly, non-traumatically into the trachea on the first pass.
To learn more about apneic oxygenation and other techniques to maximize preoxygenation, read these two excellent articles:
About the author
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Kelly Grayson, NREMT-P, CCEMT-P, is a critical care paramedic in Louisiana. He has spent the past 18 years as a field paramedic, critical care transport paramedic, field supervisor and educator. He is a former president of the Louisiana EMS Instructor Society and board member of the LA Association of Nationally Registered EMTs.
He is a frequent EMS conference speaker and contributor to various EMS training texts, and is the author of the popular blog A Day In the Life of an Ambulance Driver. The paperback version of Kelly's book is available at booksellers nationwide. You can follow him on Twitter (@AmboDriver) or Facebook (www.facebook.com/theambulancedriverfiles), or email him at kelly.grayson@ems1.com.
Comments
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John Buckner Thursday, June 28, 2012 6:40:12 PM So, everything I just learned in Basic is wrong? Everything I learned years ago at the EMT-Cardiac is wrong? Them why do we even try? All of our instructors enforced the concentrations and now you're saying they are wrong? Where are your facts (research) supporting your statements? I would like to see it. 
Kelly Grayson Thursday, June 28, 2012 8:03:00 PM Read the links, John. Dr. Levitan and Weingard offer plenty of research and supporting documentation.
And a wise doctor told me once, "Half of what is taught in medical school is wrong. It's just nobody knows which half until years later."
The same can be said of EMT and paramedic school.
So yes, much of what you were taught was wrong. Much what I was taught was wrong. Much of what I taught to my students was wrong. The only constant in medicine is the certainty that things will change.
All you can do is constantly question the status quo and keep learning. John Buckner Thursday, June 28, 2012 8:14:59 PM How the hell can we be tested and certified then? If the practice, protocols and procedures we use are wrong then are we not failing the most important precept of our job, "Do no Harm"? I questioned the new procedures and compared old versus new all the way though class and was told, "that's the way you do it, it is the best way for the patient". Kind of disillusioning... Through the years I have always reevaluated everything I did in the field be it while I was a CT and now as as Basic again. I treat my patient and not the symptoms. Patientis compensating, I know I'm on the right track, if they start to decompensate, I do something different. Not much I can do as a Basic and I have to remember I cannot act on my older training because I am no longer at that level. This is a great article just on the merit of making us reevaluate the current standards. Thanks Kelly, it was as enlightening as frustrating. Kelly Grayson Thursday, June 28, 2012 8:31:41 PM Brother, if we never changed the way we practiced, we'd still be using leeches and rotating tourniquets. Change is a good thing, even if it can be maddening sometimes.
There's a reason they call it the "practice" of medicine. ;) John Buckner Thursday, June 28, 2012 8:45:49 PM Make sense brother. Just frustrating to have the closed minds saying it's the only way. I didn't mean the first post to sound critical. It took me off guard. I like to have the information in front of me so I can understand the concept. I've had six months of "this the only way" in front of me knowing it's not. Capnography is a new concept to me as is some of the other advances. I remember the only way to monitor sats was to draw for ABG. The SpO2 sensors, biphasic monitor/defibrillators, portable vents and other equipment are new to me. I left EMS some 20 years ago and went to site safety and advanced first aid as a provider. 
Trevor Hiller Thursday, June 28, 2012 7:35:18 PM Excellent article, shared on twitter and facebook for all to see. Nice seeing not just the same old stuff about airway management. Sternal notch, NO DESAT, practical PreOx techniques.... These are actually new concepts that Paramedics aren't taught in school. 
Thomas Smith Friday, June 29, 2012 3:30:07 AM Almost everything we learn is wrong.....but that's the beauty of research-based practices. There will always be new, innovative ways to do things. 
Michael Niels Sunday, July 15, 2012 2:14:19 PM I totally agree with you Thomas. Here I would like to share a website "dissociationconstant.com" that should be useful site to visit for visitors of this post because it has lots of helpful information about dissociation constant.
Tim Hillier Friday, June 29, 2012 7:27:59 AM Kelly I am on board with everything you are saying but don't understand one of Dr Levitan's comments on quiet breathing involving flow rates of 30lpm. Could you help me with that one? My thought process was if normal tidal volume of quiet breathing is 500ml and normal resp are 12-20 then the minute volume would be 6-10l. As you say half of what we learn and teach is wrong and I am teaching something wrong here. Tim Hillier Friday, June 29, 2012 8:07:55 AM Sorry Kelly. I think I have my head around it now but I will have to rethink how I have been teaching this section. Kelly Grayson Friday, June 29, 2012 12:56:30 PM I think that he's saying for a noin-rebreather mask to provide maximal oxygenation, you need a flow rate of 30 lpm or more during quiet breathing rather than the 15 lpm we've been taught, and that if the mask fit is poor or there is labored breathing, it may take a flow rate of 48 lpm to achieve the same thing.
Jason Kodat Saturday, June 30, 2012 8:54:52 AM Kelly's right--there's a difference between minute volume and second-by-second flow rate. To get a minute volume of 6 liters, you figure you're going to spend at least half your time exhaling, so your *average* flow rate is going to be at least 12 lpm, but your actual flow rate varies by the microsecond. A half-full lung doesn't fill as fast as an empty lung, and the end of inspiration the flow rate is minimal. The reservoir bag is supposed to be there to account for this.
That said, how often do you actually see a mask fitting tightly enough for someone to deflate the reservoir bag? Tim Hillier Wednesday, July 11, 2012 7:22:50 AM You lost me again with the math. When I think flow rate I am thinking from the reg and it seems you are talking about speed of gas flow to the lungs on inhalation. Am I correct on that?
Here is what I teach and you guys can correct me where I am wrong. Attach NRB to O2 source and hold valve to allow bag to inflate completely prior to application on face. Ensure tight seal at nose with metal tab and pull straps tight to form seal on face. Watch the reservoir bag. if it is not deflating on inhalation and stays full like a balloon, decrease your flow rate as there are one of two things going on. Either you do not have a good seal or the patient is not using the flow rate your are giving. Either way you are wasting oxygen. Adjust flow rate to ensure that bag deflates on inhalation and fills between breaths. If the bag never goes down when you are down to 10l or so it is probably a seal issue and the amount of outside air coming in means you are basically using it as a simple mask anyway. If the bag deflates and does not inflate in time, increase your flow rate to maintain. I have rarely even had to keep it at 15l let alone increase to 30 or 48. It seems to work for me in practice and it is what I was taught oh so many years ago.
I dont want to continue teaching something incorrect so I am open to any feedback on this.
Thanks
Tim Kelly Grayson Wednesday, July 11, 2012 7:39:10 AM That's the way it's taught in most places, Tim, including the way I used to teach it.
The problem is, even with a good mask seal, the patient is still rebreathing CO2. Yes, I know the NRB supposedly has valves to prevent that, but at 15 LPM they don't do a good job.
So what the patient is breathing in is a mixture of CO2 and O2. We teach that a NRB delivers >90% oxygen at 15 LPM, but that is only true in theory. In actual oxygen delivery, it requires a flow rate (measured by Levitan and others) of 30 LPM in a patient with quiet, unlabored breathing, and up to 48 in a patient with labored breathing.
Since the natural path of air is primarily through the nasopharynx first, adding a nasal cannula at 15 LPM creates a "reservoir" of pure oxygen in the nasopharynx that the patient can inhale. The Adding the nasal cannula at 15 LPM to a NRB at 15 LPM will wash out residual nitrogen in the respiratory tract, and give you as close to 100% inhaled oxygen as it's possible to get without a BVM and endotracheal tube.
If you've used a NRB and a nasal cannula to pre-oxygenate someone prior to ETI, or 8 vital capacity breaths with a BVM at 15 LPM, then induce paralysis, you can maintain a good arterial oxygen saturation, even during apnea, with the nasal cannula at 15 LPM. It creates an effective pressure gradient that will continue to diffuse oxygen into the alveolar capillaries for up to 100 minutes.
Scott Lancaster Monday, July 16, 2012 9:31:34 AM Tim, Kelly's on the right track. When talking about flow in ventilation there are a couple of different meanings that are sometimes not used correctly. Your regulator sets a flow rate (15LPM), but not all of that flow is utilized in ventilation. Some is lost to ambient air through the valves, or through seal leak. Some is inhaled, and may be utilized in cellular respiration. When talking about tidal volume or minute volume in ventilation the NRB flow rate doesn't really mean much. Vt ~500cc x 12BPM = 6000cc minute volume. Inspiratory flow rates are a function of the TV, I/E ratio, and RR... Normally flows are 60-80 (and up to 100) L/min. So, when thinking about adding flow in a non-invasive setting (BMV+NC) at 25 and 25 you can reach flows of ~50LPM, increasing FIO2 in the distal oral pharax and trachea (increasing FIO2 in dead spaces) allowing for less mixed dilution on inhalation. Make sense? 
Daniel S. Syme Friday, June 29, 2012 9:36:46 AM One more reason to dispise the NREMT. Kelly Grayson Friday, June 29, 2012 12:59:42 PM Daniel, do the various state exams approach it any better, or differently? In my experience, they don't. Daniel S. Syme Friday, June 29, 2012 2:49:16 PM Yes, you have a point especially because many states like PA where I work now use the NREMTP test for their state test. It is still a game that is played to join a club. Utter the correct phrases at the correct time and put those #%&# straps on in a specific order if you want to be admitted. For Pete's sake we are putting normally curved spines on hard flat boards and claiming that will prevent secondary spinal cord injuries. There is nothing in the test which demonstrates that the student is a competent provider only that they have learned to play the game. I know that it is impossible to have a national standard and I even doubt that it is possible to have a state wide standard. Think of it, how medics practice in Philly is different from how we practice in the rural/suburban Chester County where I work and how I work is different from how medics practice in the rugged mountain counties in the center of the state. Oh my, I can go on and on and on but it will have to be saved for another time. Kelly Grayson Friday, June 29, 2012 4:14:59 PM I feel your pain, truly.
I think the solution is to recognize certification exams for what they are: a blunt tool to weed the barely competent from the totally incompetent. They're not designed to measure mastery.
To do that, I think we need tiered certification levels for paramedic - apprentice, journeyman and master - with scope of practice expanding accordingly. Daniel S. Syme Saturday, June 30, 2012 6:12:56 AM What you are suggesting is being done on an unofficial level. Where I work we rarely hire a new paramedic but if we precept a student and believe he has a lot of potential we will hire him but require him to serve an internship. The internship does not have a specific time period or even specific skill sheets to sign off on. Gradually the senior medics feel more comfortable with the new guy and give him more and more freedom until all agree that it is time to let him fly on his own. I believe that local programs designed to meet local needs work far better than inflexible national or even state tiers of certification.
James Robert Long Monday, August 27, 2012 7:39:10 PM I agree in principle Kelly but we as a proffession can't survive finacially now, if we had to go through all the hoops your talking about no one would ever make it to the master level. we can't even get standard protocols for 2 levels, just too many differing opinions. we need unity but we are inherently kep ununified by the curent system, national level, state level, regional level, local level, no two even agree on what we should be doing, no matter we are confused.
Mike Hopkins Friday, June 29, 2012 10:12:53 AM Thanks Kelly Grayson, another great and informative article! 
Vince DiGiulio Friday, June 29, 2012 1:27:04 PM One more thing about 90% being a critical O2 saturation: Because there's a lag between the reading in someone's peripheral vasculature and their true central oxygen saturation, in a critically ill patient the reading you're seeing from a finger probe is actually their sat 30-60 seconds ago. The sicker the patient, the greater the lag time, so once you see 90%, you have to recognize that you are already way behind and abort laryngoscopy immediately. Vince DiGiulio Friday, June 29, 2012 1:58:52 PM By the way, I forgot to send you a BIGGG thank you for writing this article. I've been peddling these ideas locally for a couple of years in vain, so it's nice to see a national EMS figure give them the pedestal they need to effect change on a wide scale. You rock.
Dan White Tuesday, July 03, 2012 7:51:35 PM Vince, Absolutely true. But buy an inexpensive oxiport pedi-blade
and try it sometime. It will "turn off the clock", and give you at least 3 minutes to intubate without dropping below 90% SAO2.
Jake Stein Friday, June 29, 2012 1:29:21 PM This is true only if you are on a cardiac monitor. Often the HR, provided there is on will decrease 15 seconds before the SpO2 and then the pulse oximeter will relect it after a noticeable drop according to the delay with might be another 5 to 8 seconds. Pulse ox alone is not enough. This is why hospitals will abort an apnea test in their ICU. The SpO2 might still be fine but the hemodynamics will start to dump quickly before the pulse oximeter.
The studies done by doctors and anesthesiologist were also done on patients under deep sedation in the OR without cardiac or pulmonary compromise. This will NOT work for very long on a patient who has cardiac or pulmonary compromise.
Also, if you are going to attempt a "high flow NC" at 15 L/m on a regular NC, remove the humidifier. In the hosptial they have a specially designed high flow NC that can do up to 60 L/m. Other hospitals use their ventilators or BiPAP/CPAP machines at a very high flow at 100%. Most prehospital CPAP machines can not do that or not for very long. 30% for most and if higher, the O2 tanks will drain rapidly. The Jackson-Rees bag has been used in the OR, ED and on ambulances in other countries for decades.
Nothing new. Just EMS is behind in reading the literature and other books pertaining to intubation and airway management. It is like still saying the NRB mask is a high flow device because the flow meter is set at a really high flow like "15" liters. Dan White Friday, June 29, 2012 5:45:44 PM I worked with a device that delivered oxygen during intubation and it never ceased to amaze me how well it constant flow ventilation worked. It easily doubles the time you have to intubate.Great article Kelly! 
Anthony Correia Friday, June 29, 2012 6:06:00 PM great research to practicle application article. I dont think i've put a NR on a pt. in 4 years. When I haves its been no more that 4L on NC. This article supports that practice.
Brian Simons Saturday, June 30, 2012 5:46:45 AM I have a couple comments/concerns/questions.
Dr. Levitan's states that you pre-oxygen the apneic patient using a nasal canula so that when the non-breathing patient breaths he oxyenates himself. How does an apneic patient breath? Doesn't that make them non-apneic and probably not need to be intubated? He also states that an apneic patient with a nasal cannula at 15lpm gets more oxygen than a apneic patient who is being ventilated with a BVM. How does blowing oxygen in someone's nose who is not breathing oxygenate better then me bagging the person with 100% O2 via a BVM.
How are you supposed to get flow rates of 30 or 48lpm? and how much flow can a non-rebreather take anyway? They seem like cheap plastic and would probably blow apart. I highly doubt a patient would tolerate a nasal cannula flow rate of 15lpm, that is alot of oxygen being forced in their nose, most people complain at 6lpm.
I am really confused. Jason Kodat Saturday, June 30, 2012 9:04:05 AM Levitan is probably overstating the case. The nasal cannula trick probably doesn't actually deliver more oxygen than *correctly performed* BVM. However, the oxygenation isn't provided by breathing but by diffusion down a concentration gradient.
If you haven't taken chemistry yet, I hope at least you won't be befuddled by the notion that substances move from areas of high concentration to areas of low concentration (everybody who's ever seen a drop of food coloring diffuse throughout a glass of water has experienced this firsthand). As the blood grabs oxygen in the alveoli, it creates an area of low oxygen concentration, which the high oxygen concentration in the nasopharynx can diffuse to. This is what gives the apneic patient oxygen--not any actual breathing.
If you're already bagging a pt, they're not going to notice a nasal cannula, at any flow rate. Someone who is conscious that you're about to RSI might notice, but it's not like you have it on them for more than 3-5 minutes, which is annoying but tolerable. Jake Stein Saturday, June 30, 2012 5:16:50 PM The continuous flow of oxygen is nothing knew at all. The use of a BVM is okay but you must pull away to intubate. You also must be relating the nasal cannula to the one you were taught in EMT school. The use of HFNC systems have been around for over 15 years. The use of continuous flow systems via a Jackson Rees system has been used for decades. The use of a CPAP type device has been used for at least 60 - 70 years especially in neonatal and pediatric settings. But, this is just like many of the other modalities that have taken decades to be accepted in prehospital.
You also reduce gastric insufflation, vomiting, aspiration and loss of lung volume due to gastric distention.
Now if only we can get those who do the cowboy intubations under the bed and in funky positions just to prove something to themselves instead of taking 10 seconds to move the patient we might see more successful intubations instead of esophageal placement, vomit aspiration and blood aspiration from knocked out teeth or torn palates. Kelly Grayson Sunday, July 01, 2012 5:53:32 AM You're right about the nasal cannula adding little to the BVM. It does, however, drastically improve oxygenation over a non-rebreather alone.
Read the research he cites. They were able to maintain an oxygen saturation of 98% in totally apneic patients for 100 minutes, using only a nasal cannula at 15 LPM. Jake Stein Sunday, July 01, 2012 9:41:46 AM Are you suggesting we can take 100 minutes to intubate? The pH of the blood must still be considered.
This is what his article says.
"Carbon dioxide excretion into the alveolus diminishes during apnea because carbon dioxide is approximately 25 times more soluble than oxygen in blood. It is estimated that during apnea CO2 is excreted into the alveolus at only 10 ml/min. Conversely, oxygen is absorbed at 250 ml/min. The resultant negative pressure gradient (-240 ml/min) creates a sub-atmospheric pressure in the alveolus. The net result is that during apnea, oxygen insufflated into the upper airway will be “drawn” down the trachea and into the alveolus. Oxygenation can be maintained in non-breathing humans for 100 minutes through apneic diffusion, even as carbon dioxide builds up in the blood."
Couldn't find the studies for 100 minutes. The word "estimate" is used here for CO2 so has this actually been measured? What did they use for buffering? Did the monitor ABG every 2 to 5 minutes as required for apnea testing and to monitor acidosis? What type of patients and what disclosure for experimentation was given to the families to attempt 100 minutes without ventilation?
One study from Teller said 10 minutes.
Jake Stein Sunday, July 01, 2012 9:46:43 AM The other article (Weingart) you linked had this:
"Another problem during the apneic period is absorption
atelectasis due to alveoli filled with near 100%
oxygen. The nitrogen in normally ventilated alveoli
serves to maintain their patency. When we preoxygenate
with high fiO2, our goal is to completely wash out this
nitrogen. This can lead to alveolar collapse as the oxygen
is taken up by pulmonary blood; further shunt is the
result (21)."
In a patient with respiratory compromise, how long do you want to play dare devil with the alveoli since more damage will be done reopening the alveoli in diseased lungs? Dan White Tuesday, July 03, 2012 7:48:14 PM Actually, there is no such thing as "correctly performed" BVM. There is no research ever published, which supports the use of this primitive squeeze-toy version of a fireplace bellows. Scott Lancaster Monday, July 16, 2012 9:20:26 AM The other advantage of apneic oxygenation is once you remove the BVM / NRB you leave the NC in place of 15+LPM during the intubation attempt. In practice, leave the NC at a 'normal' setting (4-6LPM) until induction (RSI) if the patient is conscious then crank it up to 15LPM until paralysis is achieved and the ETT is in place. 
Matthew Corbin Monday, July 16, 2012 5:25:31 PM Many people have no idea how medically innovative EMS has become. No longer is it "You call, We haul," but advanced medical attention + transport. 
Michael Endres Saturday, August 18, 2012 8:55:06 AM So simple and makes perfect sense! Great article as usual. Keep up the good work, brother! 
Cj Ewell Tuesday, October 16, 2012 5:01:14 PM So, what happens to the PCO2 and pH during all this apena? 
