# NC or NRB when suction is needed?



## emt58 (Apr 1, 2014)

Hi all, new EMT here with a question that I would like input. If a patient having foamy sputum constantly coming from mouth and spitting up would you still stick with a NRB when suction was frequently required? Suction was causing a gag reflex (patient was alert) and I didn't want to risk vomiting inside the NRB or more airway complications after slapping it back on so I kept a NC at flow rate of 6. Spo2 reading at constant mid 80's.


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## Brandon O (Apr 1, 2014)

If they're alert with a gag reflex, that usually suggests they can manage their own airway without you horking about with hoses. Were they on a board or something?


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## emt58 (Apr 1, 2014)

Brandon O said:


> If they're alert with a gag reflex, that usually suggests they can manage their own airway without you horking about with hoses. Were they on a board or something?



Well the odd thing is that she didn't want to spit it up willfully or when requested, also didn't want to open mouth on occasion. Horrible lung sounds and probably needed intubaton. Only when it was too much to handle would it discharge from the mouth.


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## Brandon O (Apr 1, 2014)

Was there some psych stuff? Dementia patient? Or head trauma or something?

To answer your question, a cannula is obviously preferable if there's vomiting, but you do have to consider oxygenation as well. Were spontaneous respirations adequate? If so you'll definitely want to maximize FiO2, given that droopy sat.

If we ignore the matter of protocols and such, physiologically you may be able to cheat a bit by turning the flow on a cannula up to 15 or so. Hopefully nobody would give you grief if it's legitimately the only way to manage the airway. Remember that when possible, a lateral or upright position helps keep anyone's airway clear. And that for the most part, if they have a gag reflex, they're not likely to aspirate their secretions even if it gets a bit sloppy.


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## Handsome Robb (Apr 1, 2014)

Depending on their mental status you can set up the suction and just give it to them and they can suction themselves. With that said it doesn't sound like this one would've been too keen on that.


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## mycrofft (Apr 2, 2014)

Nasal cannulas will not transfer_ much_ more flow to the pt despite being increased beyond a certain lpm.

OP, how were chest sounds, pulse and BP? WHat were you thinking, was this likely cardiac, infective, allergic, or just psych (not swallowing nor spitting out saliva)?

Oxygen, good. Suction ought to be welded to the oxygen in most cases and this is one, but if the pt seems clinically oxygenated belay that and givr her something to drool into. Sit her up!!


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## NPO (Apr 3, 2014)

If it was me, and obviously is wasn't and I don't have all information, I would give 15lpm via nasal cannula, provide suction PRN and if possible, blow by 02 if SPO2 remains low. A NRB does no one and good if she starts aspirating.


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## Mjolnir (Apr 3, 2014)

I would say I need a bit more context...as stated above, was the pt strapped t a board? If yes, then I agree, its' tricky. If not, try to have the pt maneuver to a better position and stick to the NRB.


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## mycrofft (Apr 3, 2014)

mycrofft said:


> Nasal cannulas will not transfer_ much_ more flow to the pt despite being increased beyond a certain lpm.
> 
> OP, how were chest sounds, pulse and BP? WHat were you thinking, was this likely cardiac, infective, allergic, or just psych (not swallowing nor spitting out saliva)?
> 
> Oxygen, good. Suction ought to be welded to the oxygen in most cases and this is one, but if the pt seems clinically oxygenated belay that and givr her something to drool into. Sit her up!!



Wikipedia "Nasal cannula"

AND I QUOTE:

"A nasal cannula is generally used wherever small amounts of supplemental oxygen are required, without rigid control of respiration, such as in oxygen therapy. Most cannulas can only provide oxygen at low flow rates—up to 5 litres per minute (L/min)—delivering an oxygen concentration of 28–44%. Rates above 5 L/min can result in discomfort to the patient, drying of the nasal passages, and possibly nose bleeds (epistaxis). Also with flow rates above 6 L/min, the laminar flow becomes turbulent and the oxygen therapy being delivered is only as effective as delivering 5-6 L/min."


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## Underoath87 (Apr 4, 2014)

mycrofft said:


> Wikipedia "Nasal cannula"
> 
> AND I QUOTE:
> 
> "A nasal cannula is generally used wherever small amounts of supplemental oxygen are required, without rigid control of respiration, such as in oxygen therapy. Most cannulas can only provide oxygen at low flow rates—up to 5 litres per minute (L/min)—delivering an oxygen concentration of 28–44%. Rates above 5 L/min can result in discomfort to the patient, drying of the nasal passages, and possibly nose bleeds (epistaxis). Also with flow rates above 6 L/min, the laminar flow becomes turbulent and the oxygen therapy being delivered is only as effective as delivering 5-6 L/min."



This is what they make high-flow cannulas for (up to 15 L/min).

I once picked up an ICU pt going to a hospice house that was on a special 60 L/min cannula.  The thing had huge blue prongs and required a special air pump (we switched her to a NRB for the transport, if I recall).


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## Brandon O (Apr 4, 2014)

mycrofft said:


> 'Also with flow rates above 6 L/min, the laminar flow becomes turbulent and the oxygen therapy being delivered is only as effective as delivering 5-6 L/min."



I'm gonna have to pass on an uncited Wikipedia quote with typos in it. Do you have an evidence-based source for this one?


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## chriscemt (Apr 4, 2014)

Underoath87 said:


> This is what they make high-flow cannulas for (up to 15 L/min).
> 
> I once picked up an ICU pt going to a hospice house that was on a special 60 L/min cannula.  The thing had huge blue prongs and required a special air pump (we switched her to a NRB for the transport, if I recall).



Does something like that _actually_ work?  And, really, for what need would any patient have more than 100% O2?


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## Brandon O (Apr 4, 2014)

chriscemt said:


> Does something like that _actually_ work?  And, really, for what need would any patient have more than 100% O2?



With high enough flow, it creates positive pressure (i.e. it can't leak out as fast as you're pushing it in). Essentially it's PEEP, just like if you used a CPAP.

And nasal cannulas don't provide 100% O2, although at that flow it's probably close.


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## Carlos Danger (Apr 4, 2014)

chriscemt said:


> Does something like that _actually_ work?  And, really, for what need would any patient have more than 100% O2?



Can you have more than 100% o2?


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## mycrofft (Apr 4, 2014)

Underoath87 said:


> This is what they make high-flow cannulas for (up to 15 L/min).
> 
> I once picked up an ICU pt going to a hospice house that was on a special 60 L/min cannula.  The thing had huge blue prongs and required a special air pump (we switched her to a NRB for the transport, if I recall).



I have head of these also, don't they totally occlude the nares? Wonder if the gas hisses into the oropahrynx if you open your mouth with it on? (I've seen pictures of one which also has a small prong which extends over the lips! Never seen in person though).


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## mycrofft (Apr 4, 2014)

Brandon O said:


> I'm gonna have to pass on an uncited Wikipedia quote with typos in it. Do you have an evidence-based source for this one?



I'm emailing Hudson (Teleflex) now.

The basic info for the run of the mill cannula jibes with what we were taught in nursing college and in my basic EMT class in 1977. The wikipedia article's citations are as follows:

" Nasal cannula patent (GB618570)
Jump up ^ Roca, O (2010). "High-flow oxygen therapy in acute respiratory failure". Respiratory Care 4 (55): 408–13. PMID 20406507.
Jump up ^ Hasani, A (2008). "Domiciliary humidification improves lung mucociliary clearance in patients with bronchiectasis". Chronic Respiratory Disease 2 (5): 81–6. PMID 18539721.
Jump up ^ Sim, DA; Dean, P; Kinsella, J; Black, R; Carter, R; Hughes, M (September 2008). "Performance of oxygen delivery devices when the breathing pattern of respiratory failure is simulated". Anaesthesia 63 (9): 938–40. doi:10.1111/j.1365-2044.2008.05536.x. PMID 18540928.
Jump up ^ Turnbull, B (2008). "High-flow humidified oxygen therapy used to alleviate respiratory distress". British Journal of Nursing (Mark Allen) 17 (19): 1226–30. PMID 18974691.
Jump up ^ Parke RL, McGuinness SP, Eccleston, ML. (March 2011). "A preliminary randomized controlled trial to assess effectiveness of nasal high-flow oxygen in intensive care patients.". Respiratory Care 56 (3): 265–70. PMID 21255498.
Jump up ^ Tiruvoipati, Ravindranath; Lewis, David; Haji, Kavi; Botha, John (September 2009). "High-flow nasal oxygen vs high-flow face mask: a randomized crossover trial in extubated patients". Journal of Critical Care (World Federation of Societies of Intensive and Critical Care Medicine) 25 (3): 463–8. doi:10.1016/j.jcrc.2009.06.050. PMID 19781896. "

I'll keep looking.


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## Handsome Robb (Apr 4, 2014)

Considering 15lpm via NC is now advocated for during periods of apnea during procedures such as intubation I don't agree with you, sorry boss. 

NRBs only deliver high FiO2 with a good seal, which is extremely rare. Espe ially when idiots take the valves off of them. Let me see if I can find these two articles that aren't on wiki for you.


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## Handsome Robb (Apr 4, 2014)

Here you go:

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

http://www.annemergmed.com/article/S0196-0644(11)01667-2/fulltext


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## mycrofft (Apr 4, 2014)

*Another citationed Wikipedia article, this one on high flow therapy*

http://en.wikipedia.org/wiki/High_Flow_Therapy

AND I QUOTE:*

" Nasal cannulae used for oxygen delivery usually deliver 1–6 liters of oxygen per minute. The FiO2 the percent oxygen inhaled by the patient, usually ranges roughly from 24% to 35% as the 100% O2 delivered from the cannula is diluted by ambient air (21% oxygen). Flow rates for delivery of oxygen using typical nasal cannula are limited because medical oxygen is anhydrous, and when delivered from a pressurized source the gas cools as it expands with the drop to atmospheric pressure. Delivery of cold dry gas is irritating to the respiratory mucosa, can cause drying and bleeding of the nasal mucosa, trigger bronchospasm in asthmatics, and can increase metabolic demand by cooling the body. Thus oxygen delivery by nasal cannula is limited to less than 6 liters per minute.[2]

Even with quiet breathing, the inspiratory flow rate at the nares of an adult usually exceeds 12 liters a minute, and can exceed 30 liters a minute for someone with mild respiratory distress. The typical upper limit of oxygen delivery via nasal cannula of six liters a minute does not meet the inspiratory flow rates of the average adult and therefore the oxygen is then diluted with room air during inspiration. Prior to the advent of High Flow Therapy (HFT), when high FiO2 was required for respiratory support special face masks or intubation was required. With HFT, the goal is to deliver a respiratory gas flow volume sufficient to meet or exceed the patient's inspiratory flow rate. The gas is heated and humidified to give comfortable delivery of the respiratory support….

HFT requires the use of nasal cannulae and a system designed to deliver high flow rates and the pressure generated to do so. At the same time the nasal cannula must be small enough that they do not occlude more than 50% of the nares, as this allows flow during exhalation and flush out of end-expiratory CO2 to be removed from the nasopharyngeal cavity. If the cannula did seal, the high flow volume could prevent the removal of end-expiratory CO2 and potentially produce excessive pressure in the airway which may result in barotrauma."
ENDQUOTE

Citations:
 McGinley, B.; Halbower, A.; Schwartz, A. R.; Smith, P. L.; Patil, S. P.; Schneider, H. (2009). "Effect of a High-Flow Open Nasal Cannula System on Obstructive Sleep Apnea in Children". Pediatrics 124 (1): 179–188. doi:10.1542/peds.2008-2824. PMC 2885875. PMID 19564298.

Waugh, J. B.; Granger, W. M. (2004). "An evaluation of 2 new devices for nasal high-flow gas therapy". Respiratory care 49 (8): 902–906. PMID 15271229.

 Roca, O.; Riera, J.; Torres, F.; Masclans, J. R. (2010). "High-flow oxygen therapy in acute respiratory failure". Respiratory care 55 (4): 408–413. PMID 20406507.

Waugh, J. B.; Granger, W. M. (2004). "An evaluation of 2 new devices for nasal high-flow gas therapy". Respiratory care 49 (8): 902–906. PMID 15271229.

McGinley, B. M.; Patil, S. P.; Kirkness, J. P.; Smith, P. L.; Schwartz, A. R.; Schneider, H. (2007). "A Nasal Cannula Can Be Used to Treat Obstructive Sleep Apnea". American Journal of Respiratory and Critical Care Medicine 176 (2): 194–200. doi:10.1164/rccm.200609-1336OC. PMC 1994212. PMID 17363769.

Shoemaker, M. T.; Pierce, M. R.; Yoder, B. A.; Digeronimo, R. J. (2007). "High flow nasal cannula versus nasal CPAP for neonatal respiratory disease: A retrospective study". Journal of Perinatology 27 (2): 85–91. doi:10.1038/sj.jp.7211647. PMID 17262040.

Kubicka, Z. J.; Limauro, J.; Darnall, R. A. (2008). "Heated, Humidified High-Flow Nasal Cannula Therapy: Yet Another Way to Deliver Continuous Positive Airway Pressure?". Pediatrics 121 (1): 82–88. doi:10.1542/peds.2007-0957. PMID 18166560.


*Wonder why I try to always include "AND I QUOTE"? I was told once here that simple quotation marks weren't enough. Just toeing the line.


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## Handsome Robb (Apr 4, 2014)

Did you read either the case studies or the study, with data, that I posted?

I'm thinking not. 

I hate to say it man but you're being very stuck in the old ways right now.


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## mycrofft (Apr 4, 2014)

Robb, thanks for the quick citations. They got in before that second long entry I made, it was not a response to your two replies. I'm studying them.

I'll get back when I have my reply from Hudson.


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## Handsome Robb (Apr 4, 2014)

mycrofft said:


> Robb, thanks for the quick citations. They got in before that second long entry I made, it was not a response to your two replies. I'm studying them.
> 
> I'll get back when I have my reply from Hudson.



gotcha. Sorry I'm a touch irritable today.


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## Underoath87 (Apr 4, 2014)

mycrofft said:


> I have head of these also, don't they totally occlude the nares? Wonder if the gas hisses into the oropahrynx if you open your mouth with it on? (I've seen pictures of one which also has a small prong which extends over the lips! Never seen in person though).



The prongs did practically occlude the nares.  


As Brandon O mentioned, it can create positive pressure, so I assume the RT set it up because the patient wouldn't tolerate a c-pap or bi-pap.

I think some of the confusion in this debate lies in the different types of NC's.
Robb, you mentioned NC's being used at 15L for some procedures.  But those are likely high flow cannulas which are designed to flow 15 L (they have larger diameter prongs).  Mycroft is referring to a standard cannula, which is what the OP was using.


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## Handsome Robb (Apr 4, 2014)

Underoath87 said:


> The prongs did practically occlude the nares.
> 
> 
> As Brandon O mentioned, it can create positive pressure, so I assume the RT set it up because the patient wouldn't tolerate a c-pap or bi-pap.
> ...



No, they're not, they're standard cannulas in emergent airway situations. Our flight crews do it with standard cannulas and get good results, anyone I intubate gets it as well respiratory or cardiac arrest. 

I can ask their clinical officer for the data but I'm not sure they'd give it to me. They QA each other.


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## mycrofft (Apr 4, 2014)

The citation about adding canulas to oxygen masks seemed to me to make it clear they were using standard cannulas, not special ones.

I am unable to find any studies comparing effective flow versus indicated flow in cannulas pushed beyond their rated LPM's.

Are these rates being measured by a Bourdon, Pitot, or other type gauge? Or using a regulator with dents ("clicks") in the flow meter knob which indicate arbitrarily what LPM is being issued but not actually being measured?

Bourdon style: can indicate increase in flow rate if there is an obstruction because it operates on the pressure in the curved measuring tube connected to the dial, like an aneroid sphyg. "Obstruction" in this case could be turbulence in the tubing or the nasopharynx or elsewhere.







Pitot style indicates true flow if it is close to upright and interior of the vertical chamber is dry. 






Precalibrated fixed-flow style : works only if the designated delivery style is used (cannula, regular mask, non-rebreather mask, rescue mask with headband and O2 port) because it does not truly measure flow rate. 






Bourdon and fixed-flow regulators might indicate a higher flow rate when the actual flow rate at the patient was the same or only very slightly raised because of intracannular turbulence (or other obstructions) . 

Like taking a police whistle and hooking it up to an air compressor and expecting to get a siren but all you get is a crummy dog whistle, if anything.

I'm going to try to find more about high flow cannulas.


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## mycrofft (Apr 5, 2014)

*OK enough for tonight..High flow NC*

http://www.ihe-online.com/products/...ttproducts_pi1[backPID]=1317&cHash=9c10efbbce






Shows a variety of NC sizes and flow rates at the top. It is a sales site.
==============

Oxford journals article:

http://bja.oxfordjournals.org/content/103/6/886.full

A study of 17 subjects. *See picture.* (Sorry it's so large). They have a chart comparing _closed mouth_ /HFC (high flow cannula) versus _closed mouth/regular (not NRB)_ mask. The HFC wins. :huh:


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## mycrofft (Apr 5, 2014)

*OK enough for tonight..High flow NC*

Here are two styles of increased O2 cannulas, the "mustache reservoir", and the "pendant reservoir". Each purportedly accumulates oxygen during non-inspiratory periods  then the next inhalation claims it. 




==============
Mosby's RESPIRATORY CARE EQUIPMENT (J. M. Cairo, Elsevier Books), copyright 2014, pg 93, para 4:
AND I QUOTE:
 "Oxygen flows higher than 6 L/min delivered with a traditional nasal cannula system do not produce a significantly higher F1 O2…". (red accents courtesy of mycrofft)
==============


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## Melclin (Apr 5, 2014)

At SMACCgold, Rich Levitan had some interesting things to say about the apparent superiority of nasal cannulae over face masks for many purposes (not just the apneic oxygenation during intubation for which he is well known).

Personally, I hate face masks. I always have and this trend towards NC is music to my ears. Hard to talk to the patient and despite local dogma, they don't seem to make pts feel any better purely by virtue of _looking_ like a meaningful intervention. In my own practice I raise flow rate via NC up to a limit of 6-10, depending on transport time and effect/adverse reactions. I've never really had any problems. Levitan seemed to suggest that exceeding these traditional limits in the short term was entirely appropriate, safe and efficacious. Nothing super definitive, just a compelling argument with few bits of low-LOE type papers from memory.. Talked a bit about rebreathing CO2 with most masks despite efforts to avoid this (one way valves, increased flow rates etc) and it leading to discomfort and potentially worse outcomes. Do catch his lecture if they release it.


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## mycrofft (Apr 5, 2014)

[YOUTUBE]https://www.youtube.com/watch?v=-2wXE56N8kE[/YOUTUBE]





Melclin said:


> At SMACCgold, Rich Levitan had some interesting things to say about the apparent superiority of nasal cannulae over face masks for many purposes (not just the apneic oxygenation during intubation for which he is well known).
> 
> Personally, I hate face masks. I always have and this trend towards NC is music to my ears. Hard to talk to the patient and despite local dogma, they don't seem to make pts feel any better purely by virtue of _looking_ like a meaningful intervention. In my own practice I raise flow rate via NC up to a limit of 6-10, depending on transport time and effect/adverse reactions. I've never really had any problems. Levitan seemed to suggest that exceeding these traditional limits in the short term was entirely appropriate, safe and efficacious. Nothing super definitive, just a compelling argument with few bits of low-LOE type papers from memory.. Talked a bit about rebreathing CO2 with most masks despite efforts to avoid this (one way valves, increased flow rates etc) and it leading to discomfort and potentially worse outcomes. Do catch his lecture if they release it.



Great presentation.  Doesn't it also stand to reason that if you could see the cords, the pt can breathe better even if they are just being positioned for respiratory comfort by first aid or BLS?


https://www.youtube.com/watch?v=-2wXE56N8kE


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## Melclin (Apr 5, 2014)

Yup it was. 

The link you posted isn't the same one (but I don't think it was supposed to be ) but contained a lot of the same anatomy.

I wish I had been able to jot down a few of his references. But they all changed slides so quickly. I'm sure it'll be up somewhere soon.


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## Brandon O (Apr 5, 2014)

mycrofft said:


> Mosby's RESPIRATORY CARE EQUIPMENT (J. M. Cairo, Elsevier Books), copyright 2014, pg 93, para 4:
> AND I QUOTE:
> "Oxygen flows higher than 6 L/min delivered with a traditional nasal cannula system do not produce a significantly higher F1 O2…". (red accents courtesy of mycrofft)
> ==============



That'll be the first real source I've seen for that claim. Is it cited in the text?

Usually the explanation for not exceeding a flow of 6-8 is due to discomfort and drying, which is certainly valid, but somewhat beside the point for short-term emergent situations. I have HEARD the idea that a standard cannula somehow cannot "handle" higher flow rates, but never with any serious attempts at justification, just from the same sorts of people who quote their instructors with gems like fluid loading in sepsis is to "dilute the poison."

If you like your flowmeter demo, just try it; plug a cannula into the wall O2 next time you're at work and crank it up. You can see how it easily reaches 15 liters. (Maybe you have to turn the knob a little farther than you would with, say, a NRB... if the tubing is narrower [never really compared them] there could be additional resistance -- Poiseuille and all that -- but regardless, there's pressure to spare.)


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## mycrofft (Apr 5, 2014)

I use the words "AND I QUOTE", as I explained, because one mod felt that simply using quotation marks and listing a citation wasn't enough to indicate verbatim from a source. SO, yes, it is word for word, page 93, paragraph four.

The Mosby textbook is stating (not citing a study, ?? source)  physiological findings which indicate the extra flow is not physiologically advantageous. That seems to trump any physical increase in delivery.

QUOTE: "...do not produce a significantly higher F1 O2".

I was thinking last night about how one could use a tank of water, a one liter plastic bottle, a stopwatch*, a gas cylinder with a _*pitot*_ flow meter, and a nasal cannula to test it like MYTHBUSTERS. But I'm retired, I'll have to sneak into the local ER and try it out, and make a video for DE Medic. 

If you're local to Central Calif I could rendezvous with your truck and do it sometime, with about a day notice to empty the bottle and find a big enough bucket...h34r:

*"Stopwatch"…yeah, I know "what's that?", so I'm a codger..:sad:


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## mycrofft (Apr 5, 2014)

*Pro-high flow NC treatment (sales site) with scientific studies*

They sell the equip, but the scientific papers seem good. 

http://www.fphcare.com/respiratory/adult-and-pediatric-care/optiflow/

Near the bottom it says "click here to view key clinical references".


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## VFlutter (Apr 5, 2014)

Underoath87 said:


> This is what they make high-flow cannulas for (up to 15 L/min).
> 
> I once picked up an ICU pt going to a hospice house that was on a special 60 L/min cannula.  The thing had huge blue prongs and required a special air pump (we switched her to a NRB for the transport, if I recall).





chriscemt said:


> Does something like that _actually_ work?  And, really, for what need would any patient have more than 100% O2?



We use "Salter" Cannulas for flows up to 15 L/min. They look like standard Nasal Cannulas but are green and have larger diameter tubing. They can provide ~90% Fi02.





HFNC or HHFNC is (Heated/humidified) High flow nasal cannula looks more like a Nasal pillow CPAP than a NC. It requires a humidifier and control box.  They can deliver flow rates up to 60 L/min and a Peep of 1. 

Both work great. We use Salters much more than HFNC. But HFNC is great for patients who will not tolerate a CPAP/BiPAP mask.  Many patients do better on a salters then they would with a Venti mask. 









I think a Salter NC @ 15 would be great for preoxygenation or peri-intubation.


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## mycrofft (Apr 6, 2014)

Salter's say they have  special construction.

 AND I QUOTE::mellow:
"An enhanced facepiece, larger three channel head tubing and special fittings allow flow rates up to 15 LPM".  

http://salterlabs.com/index.cfm?fuseaction=products.product&product_id=27&category_id=16

So, not the "traditional" nasal cannula.


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## ThadeusJ (Apr 7, 2014)

The theory behind nasal cannula being limited to 6 Lpm is based on the natural reservoir created by the naso-oropharynx.  It is felt that as you increase litre flow, more and more of this cavity will be filled with oxygen, creating a bolus of oxygen.  Beyond 6 Lpm, however, the cavity is filled and therefore you have reached optimal flow.  The Salter product pictured above has much larger tubing and flows that minimize room air entrainment, thus providing higher oxygen concentrations.

The American Association of Respiratory Care states 1-6 Lpm, and offers many references, but doesn't explain why in the body of the text.  Also, its a few years old, the so addition of high flow cannula aren't present.
http://services.aarc.org/source/DownloadDocument/Downloaddocs/08.07.1063.pdf


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## Brandon O (Apr 7, 2014)

ThadeusJ said:


> The American Association of Respiratory Care states 1-6 Lpm, and offers many references, but doesn't explain why in the body of the text.  Also, its a few years old, the so addition of high flow cannula aren't present.
> http://services.aarc.org/source/DownloadDocument/Downloaddocs/08.07.1063.pdf



The only paper they cite that bears upon this is this one, which unfortunately only investigates standard cannulas up to 6 LPM (they use the high-flow devices beyond that). They make the same claim about no increased flow about 6, but their citation is the same one that mycrofft quoted (Mosby).


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## Brandon O (Apr 7, 2014)

mycrofft said:


> They sell the equip, but the scientific papers seem good.
> 
> http://www.fphcare.com/respiratory/adult-and-pediatric-care/optiflow/
> 
> Near the bottom it says "click here to view key clinical references".



Doesn't seem to be anything addressing standard cannulas...


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## mycrofft (Apr 7, 2014)

Brandon O said:


> Doesn't seem to be anything addressing standard cannulas...



Yeah. And the websites are sending me sales stuff not answering with URL's or even responsive emails.

I'll tap Dr. Levitan's website. They sell his lectures.


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## Brandon O (Apr 7, 2014)

Worst case we could probably write to the Mosby editors...


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## mycrofft (Apr 7, 2014)

Have to wake them up  first probably.


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## mycrofft (Apr 7, 2014)

*OP, had enough? *

(  Sent Email off to Dr Levitan's website. )

80% of the OP's answer was in the first response I think. There is a remaining 20% is polishing the other 80%, but it is important.

1. Is the nose patent for NC oxygen?

2. Is the flow meter correct? (Right variety for the delivery device; no obstructions to fudge the results of a Bourdon or preset flow regular/gauge; if Pitot, is it virtually vertical?).

3. Have you assumed responsibility for the pt's airway by strapping them onto a board or drugging them, or is there even a real need to suction at this point? (Not bad to be ready though).


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## Brandon O (Apr 7, 2014)

mycrofft said:


> (  Sent Email off to Dr Levitan's website. )



Not exactly this topic, but I have asked Dr. Weingart whether there's evidence for their recommendation of 15 LPM for preox/apneic oxygenation, and although there's data for the general principle, that specific number seems to just be a best-guess.

Apneic oxygenation, however, is probably a different issue than spontaneous respirations anyway, since it's a different method of gas flow and insufflation (mass movement by diffusion gradient rather than an active bellows).


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## Carlos Danger (Apr 7, 2014)

Brandon O said:


> Not exactly this topic, but I have asked Dr. Weingart whether there's evidence for their recommendation of 15 LPM for preox/apneic oxygenation, and although there's data for the general principle, that specific number seems to just be a best-guess.
> 
> Apneic oxygenation, however, is probably a different issue than spontaneous respirations anyway, since it's a different method of gas flow and insufflation (mass movement by diffusion gradient rather than an active bellows).



Good points. I've been skeptical of the application of apneic oxygenation in airway management and have also been unable to find evidence in support of it. I have a suspicion that it works much better in non-difficult airways than in difficult ones.

I too am curious about the mechanics of oxygen delivery at high flow rates (say, > 6 lpm) via a non-high flow NC vs. a high-flow one. How does it work? Does it result in better oxygenation that a lower flow rate would? Is it as good a a HFNC? Etc.


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## mycrofft (Apr 14, 2014)

Dr Levitan's website does not reply.


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## Carlos Danger (Apr 14, 2014)

mycrofft said:


> Dr Levitan's website does not reply.



What was the question?


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## ThadeusJ (Apr 14, 2014)

As an aside for apneic oxygenation, when assessing brain death in the hospital, one of the tools is an apnea test.  In this test, you remove mechanical ventilation and perform a series of ABG's to see the rise in PCO2 (obviously if there are registered breaths during the test, the patient is not apneic).  In order to maintain proper oxygenation, a suction catheter is placed down the ETT to the tip of the carina and 6 LPM oxygen is piped through it.  Oxygenation must be maintained throughout the test or else the test is stopped.

Therefore, the body will absorb oxygen passively while PCO2 builds from apnea.  It is interesting to see.

Here's a link:
https://www.aan.com/Guidelines/home/GetGuidelineContent/433


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## mycrofft (Apr 14, 2014)

Halothane said:


> What was the question?



I forget...:huh:

Oh, yeah. The Levitan material says give 15 lpm via nasal cannula but nowhere does it say if that is via special high flow NC or standard or "traditional" NC. I pointed this out and asked if it was understood it was special NC. They didn't answer.


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## Brandon O (Apr 14, 2014)

As I understand it they're referring to a standard NC. This is ED-type airway management stuff.


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## Carlos Danger (Apr 14, 2014)

mycrofft said:


> I forget...:huh:
> 
> Oh, yeah. The Levitan material says give 15 lpm via nasal cannula but nowhere does it say if that is via special high flow NC or standard or "traditional" NC. I pointed this out and asked if it was understood it was special NC. They didn't answer.



Did you read the paper that Levitan and Weingart jointly authored on this subject? They state that a "normal" NC should work fine. Weingart has also made that claim on his podcasts. 

From page 6 of the paper:



> To provide apneic oxygenation during ED tracheal intubations, the nasal cannula is the device of choice. Nasal cannulas provide limited FiO2 to a spontaneously breathing patient, but the decreased oxygen demands of the apneic state will allow this device to fill the pharynx with a high level of FiO2 gas. By increasing the flow rate to 15 L/minute, near 100% FiO2 can be obtained. *Although providing high flow rates with a conventional, nonhumidified nasal cannula can be uncomfortable because of its desiccating effect on the nasopharynx, after the patient has been sedated it should cause no deleterious effects for the short interval of airway management.* Tailor-made high-flow nasal cannulas are also available that will humidify the oxygen, allowing flow rates up to 40 L/minute.



As I said before, I'm highly skeptical of the utility of the practice. There is plenty of evidence that apneic oxygenation through an NC works, just none that I've ever seen that shows it extends safe apneic time in the difficult airway patient, where airway obstruction (preventing mass flow) is a defining feature.


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## Brandon O (Apr 14, 2014)

Halothane said:


> As I said before, I'm highly skeptical of the utility of the practice. There is plenty of evidence that apneic oxygenation through an NC works, just none that I've ever seen that shows it extends safe apneic time in the difficult airway patient, where airway obstruction (preventing mass flow) is a defining feature.



I'm sure nobody would think it's effective in a complete airway blockage (e.g. laryngospasm), but that's not usually what we're dealing with in a "difficult airway." If there's literally no free passage from world to alveoli, I hope anybody who can do math realizes you don't have many options except cric.


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## Carlos Danger (Apr 14, 2014)

Brandon O said:


> *I'm sure nobody would think it's effective in a complete airway blockage* (e.g. laryngospasm), but that's not usually what we're dealing with in a "difficult airway." If there's literally no free passage from world to alveoli, I hope anybody who can do math realizes you don't have many options except cric.



Well I would hope you are right about that, but I'm not talking about complete airway blockages, anyway.

How often have you seen effective mask ventilation outside the OR? I'd guesstimate about half the time, maybe less. Usually when it isn't working it's because of soft tissue obstruction of the upper airway due to poor positioning. So here's the thing: if you can't get oxygen to pass through the airways under positive pressure, you surely aren't going to get it in via mass flow and passive diffusion. Not to mention the fact that the ability to mask ventilate obviates the need for passive oxygenation, anyway. The airways that you really need apneic oxygenation to work on are exactly the ones that the technique is the least likely to work on.

I'm not saying it shouldn't be done or that it would never be helpful, I'm saying I don't think it makes a very good safety net for the difficult airway.


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## Brandon O (Apr 14, 2014)

Halothane said:


> How often have you seen effective mask ventilation outside the OR? I'd guesstimate about half the time, maybe less. Usually when it isn't working it's because of soft tissue obstruction of the upper airway due to poor positioning.



I think that's too strong of a claim. Sometimes the airway is totally blocked (often, as you say, due to inadequate positioning). But it may only be narrowed, which makes things difficult, particularly if it tends to favor airflow down the esophagus. Or it may be transiently difficult (as in, you're not locked into a solid setup that you can reliably bag into, but as you move them around you keep opening and closing the airway), which would allow intermittent passive flow. And many times the challenges are merely due to mask seal.

Filling the pharynx with passively-insufflated oxygen is a safety net. You shouldn't be relying on it, and you should be doing your best not to need it. But it takes little time and has negligible harms, and may help "cover your mistakes" when you're not perfect, which is exactly the sort of thing that's helpful for building a layered approach -- you want stuff you don't have to think about behind the stuff you're actively working on.


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## mycrofft (Apr 14, 2014)

Halothane said:


> Did you read the paper that Levitan and Weingart jointly authored on this subject? They state that a "normal" NC should work fine. Weingart has also made that claim on his podcasts.
> 
> From page 6 of the paper:
> 
> ...



I've cited sources stating 15 lpm through a device designed not to deliver that amount will not do it by simply turning it up* due to disruption of laminar flow, and noted that Bourdon and fixed flow rate regulators will give you an erroneous reading due to the Bourdons' tendency to overrate flow if pressure climbs (as in blockage) and the regs with little numbers and detents on them which are pre calibrated to an open airway and the designed device being on the end of a reasonable length of hose. *Yes you can probably push more through but it won't be "fifteen" unless your pitot (little ball in the column) says fifteen*. In the case, gauges can lie.

That said, flooding the naso-oropharynx with oxygen works if/when it is pumped down the airway or the pt inspires; filling this potential dead space with O2 is overcoming seal issues etc with masks alone. I cannot believe flooding the naso-oropharynx with oxygen then just leaving it there (total apnea and blocked airway) will diffuse any appreciable oxygen into the pt, as some folks replying here seem to maybe think. A blocked nose will deny that avenue to feed in naso-oropharyngeal oxygen. 

The healthy lung's lining, if microscopically flattened out, has an absorptive surface area approaching that of a tennis court; the oropharynx, that of a medium sized bandana if that, and it is not specifically designed for gas exchange. Reference is made at some points to setting up a high flow NC then putting the respirator mask over it.



* I call this the Spinal Tap Phenomenon.


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## Brandon O (Apr 14, 2014)

mycrofft said:


> That said, flooding the naso-oropharynx with oxygen works if/when it is pumped down the airway or the pt inspires; filling this potential dead space with O2 is overcoming seal issues etc with masks alone. I cannot believe flooding the naso-oropharynx with oxygen then just leaving it there (total apnea and blocked airway) will diffuse any appreciable oxygen into the pt, as some folks replying here seem to maybe think. A blocked nose will deny that avenue to feed in naso-oropharyngeal oxygen.
> 
> The healthy lung's lining, if microscopically flattened out, has an absorptive surface area approaching that of a tennis court; the oropharynx, that of a medium sized bandana if that, and it is not specifically designed for gas exchange. Reference is made at some points to setting up a high flow NC then putting the respirator mask over it.



The physiology here is not that the patient absorbs oxygen through the pharynx.

It's more along these lines:

1. Oxygen is absorbed in the alveoli (a passive process; dead people can do this)

2. CO2 is exchanged in the opposite direction, but NOT as readily, largely because it's nice and soluble in blood and likes to stay there unless we maintain a steep A-a gradient

3. Since we're sucking more gas out of the alveoli than we're putting back, a negative pressure develops there

4. Negative pressure sucks gas out of the pharynx, where we've been storing lots of pure oxygen

5. This gradient continues to flow until so much CO2 builds up that we no longer have a negative pressure (plus, um, it's bad for you).


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## Carlos Danger (Apr 14, 2014)

Brandon O said:


> Filling the pharynx with passively-insufflated oxygen is a safety net. You shouldn't be relying on it, and you should be doing your best not to need it. *But it takes little time and has negligible harms, and may help "cover your mistakes"* when you're not perfect, which is exactly the sort of thing that's helpful for building a layered approach -- you want stuff you don't have to think about behind the stuff you're actively working on.



I completely agree. Placing an NC before you intubate will almost certainly not hurt, and it just may help in some cases. If I were a medical director it would be in my agencies' protocols.

However, I'm sure you would concede that there are times that it just won't help much or at all. Nothing is perfect, right? All I'm saying is that those times are likely to be the times that you need it most.


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## Brandon O (Apr 14, 2014)

Halothane said:


> However, I'm sure you would concede that there are times that it just won't help much or at all. Nothing is perfect, right? All I'm saying is that those times are likely to be the times that you need it most.



Certainly possible. I would like to see more data on this in sicker folks, but of course, it's hard to do those studies. It'd probably have to be something like an outcome analysis of a big cohort where you randomized half the folks to get the cannula and see whose sats dropped the most, who did better, etc.


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