Optimal Pre-Oxygenation?

Pre-oxygenation is a vital part of airway management immediately prior to intubation and any situation where airway control is taken away from a patient.

We often overestimate our ability to predict airway difficulty – in one study of 3991 difficult intubations 93% were unanticipated (see here). Further the NAP4 study has revealed that airway difficulty is encountered 60 times more frequently in critical care environments than in anaesthesia (see here).

Pre-oxygenation should be performed in the best way possible to provide the greatest time for successful airway control before a patient suffers hypoxic tissue damage.

The Difficult Airway Society have generated guidelines discussing pre-oxygenation in detail (see here).

The DAS guidelines stipulate the requirement for a face mask seal: ‘De-nitrogenation can be achieved with an appropriate flow of 100% oxygen into the breathing system, maintaining an effective face-mask seal’.

Non-rebreather masks (NRM) do not provide a face mask seal. The use of NRM for pre-oxygenation appears to be a culture in some emergency departments. In changing this culture we may provide our patients with a significant increase in the safety of their care.

It is concerning that there appears considerable deviation away from recommended practice. This is of significant detriment to patient safety and warrants further review.

 

There are a number of disadvantages to using an NRM compared to using face masks which allow a seal:

1. The efficacy of an NRM (even with supplemental nasal prong oxygen) for pre-oxygenation is significantly less than that with masks which allow a seal. An NRM is not designed to create a seal on the patient’s face. As a result air is likely to be entrained decreasing the amount of oxygen delivered to the patient. Click image below for study comparing modes of pre-oxygenation by Groombridge et al:

Click on the image below for a further study looking at similar outcomes by Hayes-Bradley et al:

 

2. An NRM does not offer a means of ventilation

– A device which allows ventilation will be required after the airway has been established.

– A means of ventilation will also be required in the event that intubation is unsuccessful – if a BVM has been used for preoxygenation it is immediately available and checked should this need eventuate.

– The DAS guidelines state that for RSI ‘mask ventilation with 100% oxygen should begin as soon as possible after induction of anaesthesia.’ The benefits of this are huge: (i) maintaining oxygenation (ii) knowing whether or not the patient is mask ventilatable at low pressures prior to intubation. These benefits often outweigh the risks of aspiration which also need to be taken into account. The anxiolytic effect on proceduralists of both of these benefits must not be underestimated – allowing clearer thought processes in an often stressful situation.

3. An NRM is an additional (and may be an unnecessary) piece of equipment which needs to be obtained in an often stressful situation. Additional equipment adds increased complexity detracting focus from the job at hand.

4. Often patients requiring intubation in emergency settings have a decreased level of consciousness and are at risk of airway obstruction. When using an NRM, for reasons discussed below, this obstruction may go unrecognised – the patient may be receiving no oxygen at all through the obstructed airway.

5. The leak around an NRM impairs gas sampling when gas sampling is used (and it should be). The DAS guideline states: ‘De-nitrogenation can be achieved with an appropriate flow of 100% oxygen into the breathing system, maintaining an effective face-mask seal until the end-tidal oxygen fraction is 0.87–0.9’. This indicates the need for an oxygen gas analyser to assess adequate oxygenation prior to induction.

6. To overcome the lower FiO2 from air entrainment around the NRM those who use this technique try to compensate for this by delivering even greater flow rates. This high flow of gas into the mask further impairs gas sampling.

7. Using extremely high oxygen flows in environments where oxygen supply is finite can lead to oxygen supply depletion – patients are then left without oxygen for resuscitation.

8. Gas sampling of both oxygen and carbon dioxide is almost essential to ensure adequacy of pre-oxygenation. Many emergency departments have capnography, most do not have oxygen analysers. There is a possibility they may not be delivering oxygen to the patient at all – it is not uncommon for staff to forget to connect the gas tubing to the oxygen source. Further there have been numerous reports of oxygen pipeline failures and crossovers (see here) – in one emergency department over 300 patients received nitrous oxide instead of oxygen before this issue was noticed – unfortunately by this time 27 patients had died as a result. This is not an issue which has been relegated to history, pipeline crossovers occur regularly and continue to cause unnecessary deaths throughout the world.

Perhaps the lack of oxygen analysers in particular environments has allowed a culture of pre-oxygenation with an NRM to persist in these departments. Without sufficient feedback we rarely improve.

Please note – pulse oximetry alone provides very poor feedback on the efficacy of pre-oxygenation or airway maintenance. The majority of patients oxygen saturations will be close to 100% despite no pre-oxygenation. There is also a significant delay between loss of oxygenation and a change in oxygen saturations. This makes the use and feedback obtained from oxygen analysers and capnography of even greater importance.

Further NAP 4 has shown us that airway difficulties are 60 times more common in critical care environments than anaesthesia making oxygen analysers and other other optimal equipment even more important.

9. Disconnecting oxygen from an NRM to the device required for ventilation requires an additional unnecessary step.

10. Disconnecting a gas sample line from an NRM to the device for ventilation requires an additional unnecessary step. Any additional steps increase complexity in what is often a staff limited and stressed environment.

 

Dr Nicholas Chrimes discusses the principles of pre-oxygenation in more detail (see here).

Please note that the assessments performed by Dr Nicholas Chrimes have been carried out on healthy patients where a patent airway is guaranteed.

Often when patients are intubated in ED it’s because of a threatened airway – the airway is dynamic and may potentially obstruct during the preoxygenation phase – this is readily recognised when waveform gas analysis is used. Where it is not, for example with a non rebreather, airway obstruction may mean the patient is not receiving any oxygen at all. Where it is, for example with a face mask seal, attempts can be made to rapidly open the airway, with great feedback as to whether this has been done, and ventilatory support be provided immediately pending intubation.

 

Reasons provided for use of an NRM for pre-oxygenation have included:

A. ‘Holding a Bag Valve Mask or Mapleson Circuit for pre-oxygenation requires a level of skill that the person managing the airway may not have’. Holding a mask that obtains a seal is not a difficult skill to obtain particularly with the feedback of gas analysers. This skill should be one attained by any staff member given charge of looking after a patient’s airway.

B. ‘Using a non-rebreather mask frees the staff member up to perform other tasks’. There is much that needs to be done in the period prior to intubation – staff and equipment readied and checked. If the staff numbers are insufficient to dedicate an individual solely to provide preoxygenation at this time then an NRM may be suitable while the environment is readied. However in the period immediately prior to induction optimal preoxygenation needs to become the primary focus at this time – change from the NRM  to a face mask seal and ensure preoxygenation is performed optimally.

C. ‘Patients may be intolerant of a mask with a seal on their face (they may be claustrophobic)’. There are many methods to help overcome this issue including having the patient hold the mask themselves, sedating the patient, holding the mask increasingly close to the patient as they become more sedated eventually attaining a seal…. This certainly is not a reason for an NRM to be used routinely for pre-oxygenation. Administering a small dose of induction agent, in effect sedating the patient, will likely allow them to tolerate the mask and where a face mask seal (e.g. BVM) then one is immediately able to ventilate the patient should the patient become ‘over’ sedated.

Perhaps one might be more likely to keep a mask on a patient when you are holding on to it.

D. ‘There is an increased work of breathing when a patient is spontaneously breathing using a Bag Valve Mask’. The picture below demonstrates that the inspiratory valve of a laerdel bag is already open without any effort from  the patient when an oxygen flow of 15L/min is delivered into the bag.

We will note there was a decrease in ease of breathing noted by patients in Groombridge’s study when using BVM compared to NRM.

There is misunderstanding by some doctors that the bag of a BVM needs to be squeezed to deliver oxygen to the patient (leading to further inappropriate concern that has will then be insuflated into the patient’s stomach increasing the risk of aspiration) – as can be seen from the image above this is not the case.

E. An historical and potentially detrimental belief by some is that mask ventilation is absolutely contraindicated in the phase of rapid sequence induction between administration of induction drugs and patient apnoea up until the time of intubation.

There is a real risk of aspiration during this phase and insufflation of the stomach will increase this risk – however low pressure mask ventilation (below barrier pressure) in those with an intact lower oesophageal sphincter and/or no significant history of reflux should not increase this risk significantly. Low pressure mask ventilation is easier to attain with an anaesthetic circuit with an adjustable pressure limiting valve set for example to 15cmH2O – this may not be readily available in emergency departments.

Their is great value in mask ventilation during this phase which should not be underestimated for two main reasons:

(i) oxygenation is maintained

(ii) an assessment is made as to whether a patient can be ventilated at low pressures which impacts on the consideration that the patient cannot be intubated. If they can be mask ventilated this relieves the intubator of a vast amount of psychological pressure and naturally they become more relaxed and are able to think more clearly in a calm manner. If the patient can’t be mask ventilated at low pressures the intubator can already be considering the need for additional airway adjuncts (Guedel, LMA etc) in the event that they cannot intubate the patient.

This article from Canadian Journal of Anaesthesia (see here) from 2007 discusses each component of Rapid Sequence Induction – see section 8 for a discussion on the benefits of mask ventilation prior to intubation. The use of mask ventilation prior to intubation is also supported by the Difficult Airway Society Guidelines (see here).

G. Proponents of NRM use for preoxygenation discuss ‘overcranking’ the flow meter to deliver >15L/min of oxygen flow. Studies have shown that when ultra high flows of oxygen are used >40L/min into a NRM then similar FiO2s may be reached to those delivered with a face mask seal (see here). However these results must be extrapolated with caution to the clinical population. Use of high oxygen flowrates is suboptimal due to unregulated/measured flow and some flowmeters do not allow these flow rates. Sometimes the pressure generated by these high flows causes the oxygen tubing to pop off. It has been shown that oxygen flowmeters in Australia do not provide flow rates of greater than 19L/min (see here) and subsequently do not provide optimal FiO2 (see here).

 

Perhaps the outline below, based on the DAS guidelines and input from several experts in airway management, represents a simplified approach to optimal pre-oxygenation:


Please forward this on to others for discussion and support the introduction of gas analysers in all areas of resuscitation (see here). While conditions may vary with patient, physician and environment it is vital that we understand and adopt the best approach to pre-oxygenation for optimal patient care.

The culture of NRM use for pre-oxygenation seems to be particularly prevalent in emergency departments in the United States where emergency physicians primarily manage patients airways. This culture may have existed for some time. It may also have been perpetuated by several dedicated, respected and influential emergency physicians (see here):

We ask that they work with anaesthetists and other experts in airway management to review their recommendations to ensure an optimal approach to pre-oxygenation.

It is time to stop the culture of non-rebreather mask use for routine pre-oxygenation and limit its use to those rare cases where it may be beneficial (e.g. in cases where it’s impossible to obtain a face mask seal and there is no access to THRIVE)?

Further it has come to our attention that in some countries BVMs do not come with an expiratory valve as standard. BVMs without an expiratory valve will entrain air during spontaneous ventilation during preoxygenation significantly impairing preoxygenation. We are working with airway experts to create a list of BVMs with and those without expiratory valves (see here).

Thank you.

 

Below we provide several tweets from physicians and paramedics expressing concern about the use of NRM for pre-oxygenation:



5 Comments

  1. I am an emergency medicine physician in the US so I think I can bring the appropriate context for this discussion. I have an interest in airway management as well as pre-oxygenation strategies. Unlike some posters I don’t think people are “morons” for using a NRBM for pre-ox in some patients. Should it be routine? No- because there are some patients that may require a different pre-ox strategy for optimal outcomes. However, in a large percentage of patients that we see, it may be a completely appropriate pre-ox strategy but only when done at “flush rate” (approximately 50-60 LPM, detailed below).

    First I think some historical context is necessary. I started my EM training as an intern (1st year registrar) in 2009- coming up on 8 years ago. When I started, no one paid attention to pre-ox before RSI. Sure, all patients were on NRBM at 15 LPM prior to intubation but there was no apneic oxygenation (ApOx) and I never saw anyone pre-ox’d with a BVM or NIV. This was also when VL had only gained a small foothold in the ED. I can only recall a single intubation I did in the ED that year with a glidescope hyperangulated blade- it was all DL.

    The results were very predictable- once the NRBM came off, even if the tube was placed in a matter of 10-15 seconds, the patient would almost always transiently desaturate to the mid to high 80s. They would be bagged back up and all would be well if the tube was actually in the trachea. So the state of EM pre-ox around 2010 was not great to start with.

    This continued until about midway through my second year of training when Rich Levitan published NO-DESAT (ApOx at 15 LPM with NC) in a “throwaway” EM magazine. I smacked my forehead and wondered why it took us so long to figure this out. Suddenly, none of my patients desaturated (unless the RTs took the NC off despite me telling them not to). I have been using NO-DESAT for the past 5 years and I can count 2 instances of desaturation and second attempts required at an airway due to desat out of hundreds of ED RSIs in that same time period.

    Then Weingart and Levitan’s pre-ox paper came out in Annals and pre-ox for RSI got a lot better. That paper opened a lot of people’s eyes (mine included) to all the different strategies we could use in order to maximally pre-ox patients and prevent desats during RSI.

    One of the recommendations in this paper is that a NRBM with its valve turned all the way open (now known as “flush rate”) could produce oxygen flows of 30-60 LPM and FiO2s of 90% instead of the 60% for a NRBM at 15 LPM. This was a quick, easy, and “free” way to dramatically increase the patient’s oxygenation and pre-ox patients a large percentage of patients that we see in the ED. I started doing this in my practice and watched patients who were saturating in the mid-80s on a NRBM rise to 100% when flush rate was done.

    However- there is a problem with this claim of the NRBM having a much higher FiO2 at flush rate. The citation provided for this was an abstract at a respiratory therapy meeting- not a peer reviewed study. This citation is now unavailable online so you cannot even scrutinize the abstract of this study.

    So the question is- how does NRBM compare to BVM in terms of pre-ox? First I think we should state that all of these studies use healthy volunteers and measure end tidal oxygen levels as a surrogate for pre-ox. End-tidal oxygen levels are not a patient oriented outcome. I have looked but have not found a study that has related increasing EtO2 levels to improved intubation outcomes. If anyone knows of such studies, please send them to me, as I would be interested in reading them. If we accept that EtO2 is an adequate measurement of pre-ox then the studies on this issue can be used to tell us the best option for our patients. However, as far as I know, this remains an unproven measurement in regards to increasing safe apneic time or rate of first pass success. These are outcomes that patients would care about.

    Until recently we did not have an answer as to how flush rate oxygen performs as compared to the standard NRBM at 15 LPM. However, Driver et al in the December Annals of Emergency Medicine (PMID 27522310) demonstrated that EtO2 readings from NRBM at flush rate (55 LPM) was 86% vs. NRBM at 15 LPM of 77%. This difference was not statistically significant- it was a non-inferiority trial of 23 subjects.

    However, there is a signal here that NRBM may give higher EtO2 measurements than a BVM. With a larger sample size and a superiority study design, flush rate NRBM may actually be better than BVM based on EtO2. As an aside, in speaking with the author they have looked at BVM at flush rate and their initial data suggests that it does not seem to increase EtO2 over 15 LPM.

    One could argue that we cannot be certain that a oxygen regulators cannot reliably deliver flows above 15 LPM and that is a valid criticism. That has not been my clinical experience and an internal study at my last position found that all regulators in our ED could get to at least 60 LPM of flow. Some reached an ear-splitting 130 LPM of flow with the valve open all the way. I support the argument made by John Sackles that we should have regulators in the ED that go up to 70 LPM so we can be certain that we are providing this extra flow.

    My point here is that NRBM at flush rate may actually be superior to BVM in terms of driving up EtO2- right now we know it is non-inferior. Hayes-Bradley et al used a 5% margin to signify a clinically important increased in EtO2- the difference here was 9% although it is a non-inferiority design. Therefore, it is a valid argument to make that a NRBM at flush rate may give the same quality of pre-ox as a BVM, as measured by EtO2.

    However, there is a recent paper from Groombridge et al (PMID 28295147) that gives me pause. In their study, the oxylator 3000 NIV with a 5 of PEEP got volunteers to 95% EtO2. My experience with a Phillips respironics NIV machine with a 10 of PEEP is an EtO2 in the high 70s (similar to a BVM). This particular finding is an outlier in all of the pre-ox studies and I don’t know what to make of it. The only difference I could find in study methods is that these subjects were supine instead of semi-recumbant like all other studies. I am not sure if that could account for different readings- if anything being supine should decrease your EtO2 due to suboptimal position for respiration.

    Next, let’s consider the two broad categories of patients who receive RSI in the ED when divided by their pre-ox needs- patients who are being intubated for expected clinical course (mostly those with altered or declining mental status) and those who have oxygenation or ventilation issues.

    In a patient who is being intubated due to poor mental status who is spontaneously breathing, is not hypoxic at baseline, and has no significant shunt or lung pathology, a NRBM at flush rate may be an appropriate pre-ox strategy. These patients can inhale sufficient tidal volumes from a high FiO2 source and pre-ox without difficulty.

    In patients with significant shunt or hypoxia I completely agree that a NRBM (even at flush rate) is not appropriate- at least not as the final pre-ox strategy. In the ED, I may quickly throw the patient on a NRBM at flush rate as the first maneuver as I am setting up a BVM or a NIV machine but these patients will get NIV or BVM pre-ox. A NRBM is very quick to apply and will give me time to set up a better pre-ox strategy. These patients clearly require PEEP in order to maximally pre-ox and overcome that shunt that is present.

    In my practice, I cannot say with any certainty which patients fall into the first category and which fall into the second category. I will say that a not insignificant percentage of my patients fall into the first category- I just can’t say exactly how many.

    All of that being said the big overarching question is why would you use the NRBM if you have a BVM available? Why not hold the BVM in place and pre-ox that way?

    From a person who practices in the ED, it comes down to provider resources. Patients in the ED may arrive with little or no advance notice and require immediate pre-ox for intubation. There are also many other tasks that have to be accomplished such as patient assessment, placement of monitoring equipment, IV access, decisions on treatments, managing the resuscitation, etc. that all must occur at the same time. While at my main position at an academic level 1 trauma center, I have help in spades. More times than not I have to play crown control in order to reign in the chaos. So in that situation, I may be able to dedicate one provider to focus on nothing but holding a mask seal.

    However, the “big game” in EM is single coverage in community (non-academic) hospitals. In those hospitals, I may be the only provider at the patient’s bedside. I cannot focus on holding a mask seal on a patient who has just presented with altered mental status while also running a resuscitation. While I may have help from a respiratory therapist, sometimes they are not available. Anyone who insists that it is practical to stand there and hold a mask seal has not practiced in a US Emergency Department for an significant amount of time as a single coverage physician. In that situation, your focus and mental attention is much better served on running the resuscitation to improve the patient’s overall state prior to intubation rather than focusing on holding a mask seal.

    This is why EM physicians like NRBM to pre-ox. NRBM pre-ox is simple and doesn’t tie up a provider to hold a mask seal on a patient who will not likely cooperate with it. While cooperation can be facilitated with medications (and Delayed Sequence Intubation has radically changed my practice on this), that may not be the most practical step. We now have evidence that in spontaneously breathing volunteers without shunt, flush rate NRBM is non-inferior to BVM pre-ox.

    While NRBM may not be optimal for all patients, pre-ox in emergency airway management has improved by leaps and bounds over the last 8 years. We now know to pay more attention to this area and this is resulting in increased patient safety. In conclusion, I do not recommend ROUTINE use of NRBM for pre-ox. However, flush rate NRBM is an acceptable strategy in certain patients- namely those who are spontaneously breathing, are not hypoxic, and do not have shunt physiology.

    Future directions include the use of real time EtO2 sensors to monitor pre-ox in the ED. These sensors are not widely available in EDs but I believe that future research will show that there is value to measuring EtO2 to assess pre-ox prior to ED RSI.

    I would certainly be interested in participating in a discussion on this issue as long as terms such as “morons” can be avoided (as posted in a twitter message above). I have an interest in airway preox and I want to learn from other specialties while others acknowledge what I have learned from my own training and respect the environment where I work.

    Steve Carroll, DO
    Assistant Professor of Emergency Medicine
    Emory University School of Medicine
    @embasic
    steve at embasic dot org

    • patientsafe@icloud.com

      Hi Steve,

      Thank you for providing an excellent in depth history of pre-oxygenation in American emergency departments. It makes it much clearer to me why the approach of NRM use has originated and persists in many environments.

      I believe that when waveform oxygen analysers becomes available in emergency resuscitation environments then ED doctors will quickly see the disadvantage of this technique. Perhaps consider why use of NRM is not routine in operating theatres and why anaesthetists would use a mask which provides a seal when pre-oxygenating patients in ED.

      I respect there is much that needs to be done in managing critically ill emergency patients (obtaining equipment etc) however I would point out that at the time of pre-oxygenation immediately prior to intubation perhaps this is the most important step in ensuring patient survival. An optimal airway and breathing/oxygenation precedes everything else. (Perhaps the only instance where this may not be the case is in a patient who has arrested where primary focus is on cardiac compressions and defibrillation).

      It may be different in American emergency departments but in much of the rest of the world a staff member is dedicated to looking after the airway. Perhaps you might be able to enlighten us on this.

      I accept that in perfect conditions the FiO2 delivered with flush rate oxygen delivery into an NRM may reach levels provided with a face mask seal. However in losing capnography (and oxygen analysis) through doing this the best assessment of airway patency is lost. How often will this oxygen be flushed into an obstructed airway?

      Is the use of flush rate O2 a conscious/subconscious attempt to maintain support for a suboptimal practice in using NRM? For in changing to doing something simpler and often more effective with a face mask seal one will have to accept that the previous way of doing things wasn’t as good – and unfortunately in healthcare this often means patients have been harmed unnecessarily – a very hard pill to swallow.

      Given my interest in the human factors approach to patient safety I’m a big fan of simplicity with effectiveness. Use of an NRM often adds an unnecessary piece of equipment to a stressful environment – if a mask seal with a bag is used for pre-oxygenation it is ensured in being immediately available for ventilation on intubation and also immediately available for bag mask ventilation should intubation fail.

      Perhaps the only situation where NRM may be of advantage is if THRIVE is not available and facial anatomy (e.g. from trauma) prevents a mask seal being obtained.

      I apologise for keeping the word ‘morons’ in the post. These are not my words but those of an emergency physician from the UK. I have kept it in the post because of the effect it has – it provides a strong polar opinion which may upset but has also made people pay attention.

      Optimal pre-oxygenation is a vitally important topic. If, as you point out, NRM is not the appropriate choice for optimal pre-oxygenation and we manage to change this historical and cultural practice where it exists to one which is better for patient care can you imagine the number of lives that may be saved?

      Thank you again for your most informative comment.

      Please do reply and keep the discussion going – it is through transparent disinhibited communication that patient safety will improve.

  2. I appreciate your response and I recognize all of the points that you make with your post. Mainly that NRBM adds an extra piece of equipment, does not allow for continuous end-tidal oxygen monitoring, and does nothing to ensure airway patency. I agree that these are disadvantages of this approach. Regarding the airway patency issue, no one is leaving these patients alone so obstructed airways should be recognized relatively promptly. An end-tidal CO2 detector placed under the mask could detect apnea when using NRBM. I do this frequently when providing procedural sedation in the ED and I still get excellent end-tidal tracings- even at flush rate. My only hesitation in using this approach is that the current end-tidal NC that are used are not rated to deliver flows required for ApOx- the manufacturer will only guarantee that 6 LPM can go through the prongs.

    As far as adding another piece of equipment, this is a disadvantage. However, I see this as being outweighed by freeing up the operator to perform other tasks that may be much more urgent. Could we compromise and say that NRBM at flush rate can be started initially and then switched to BVM with a mask seal immediately prior to sedative administration?

    John Sackles has been looking at the issue of using end-tidal O2 administration to guide pre-ox. He has yet to publish on this specific technique but in conversations with him, he is still able to get end tidal readings that are not completely flushed out by the flows from a NRBM. I will not speak further on this as I do not have any data- peer reviewed or otherwise to back this up. I suggest that you invite John to post here. I agree with you that end-tidal oxygen measurements should probably be available in the ED and used. However, just as techniques used in other environments, uptake of this in the ED has lagged- reference end-tidal CO2 which used to be relatively cutting edge when I first started training, now it is virtually standard of care. I will point out that I have never seen end-tidal oxygen readings used in the ICU or other out of operating room settings where emergency airways are performed.

    One area you did not address is the non-inferiority and possibly superiority of NRBM at flush rate in regards to EtO2 levels. Let’s suppose that we replicated Driver’s study with larger numbers with the goal of being a superiority study. Let’s then say that we found the same margin of superiority in EtO2 levels at 9%. Is that not a reason to say that NRBM at flush rate could be superior to a BVM for pre-ox in spontaneously breathing patients? An increase of 5% in EtO2 should give approximately 2 extra minutes of safe apnea time- is an increase of 9% not clinically significant enough? What would be your threshold of superiority be before you would accept that a NRBM at flush rate is superior to BVM?

    With all that said, I think HFNC/THRIVE will make this argument relatively obsolete. With the ability to not only provide apneic oxygenation but (at least some) apneic ventilation as well, I think this will radically change how we approach emergency airways in terms of pre-ox and ApOx.

    Thanks for your thoughtful reply- I am happy to discuss further. I realize that you were not the one to post the “morons” comment- just wanted to keep it civil (which this certainly is).

    Steve

    • Sorry- had a mistake in the post and can’t go back and edit it- 5% increase in EtO2 should equate to 30 extra seconds of safe apnea time per Hayes-Bradley which referenced this study- http://link.springer.com/article/10.1007%2Fs12630-009-9084-z

      • patientsafe@icloud.com

        Thank you Steve again for your valuable response,

        I agree yes an NRM could be placed on a patient in whom one is satisfied with airway patency and adequate respirations freeing one up to perform other tasks (e.g. obtaining equipment). At the time of pre-oxygenation then yes I would support applying a face mask seal (BVM or anaesthetic circuit) and I would encourage all to apply the waveform gas analyser at this point – with an oxygen analyser aiming for an ETO2 of >90%.

        Waveform gas analysis (capnography and oxygen analyser) is perhaps by far the current best method of assessing airway patency. I view not having waveform gas analysis as a huge detriment to airway management. I am concerned and have observed how ultra high gas flows flush away gas and make it difficult/impossible for gas analysers to read.

        That said yes I have used and observed the use of THRIVE on several occasions and the apnoeic time it provides with a guaranteed patent airway is certainly very impressive. The only down side is that it’s use leads to us losing our best monitor of airway patency (gas analysis) – I am concerned that it may be used without effect in patients whose airway obstruct and this goes unrecognised.

        I have and will continue to communicate with Dr John Sakles and invite him to comment also. He has access to waveform oxygen analysis in the emergency department. When I last spoke to him he could obtain a static number for his ETO2 and is looking in to how to display the waveform – I believe this may be vital in reviewing how effective flush rate NRM use is in real time.

        Thank you again Steve.

        I am extremely appreciative of the time and effort you’ve put in to openly discussing this vital topic.

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