Mythbusting

[Smellypaddler]

OK, it's mythbusting time. I heard these three today and went looking for evidence to prove or disprove them. I'm not looking for "In theory it is this but in practice it is different" answers. I am looking for reputable evidence to inform my practice.

I can't base my practice upon tradition, myth or the answers of an internet forum so I am hoping that some on here may know of studies to back up or disprove the following:

1) Palpable pulses correlate to varying blood pressures depending on location. I.e. Radial = >80mmHg, Carotid =>40mmHg
This has been consistently taught throughout my last 4 years at university, is it true?

2) Giving high flow oxygen to COPD patients who are hypoxic and suffering an exacerbation will knock off their respiratory drive?
Todays class was about using nasal prongs first or only 6LPM via Hudson mask. I found information saying that this may be able to happen in theory but the amount it actually occurs makes it statistically insignificant. Any studies out there that give a definite conclusion?

3) Cricoid pressure should be used during intubation to stop regurgitation and ensure a better view of the vocal cords.
I was recently participating in a workshop with an emergency consultant who said that they no longer perform cric pressure as it doesn't work and that, although slow, the rest of medicine is slowly catching up with this concept. Again any evidence?

 

[Mariemt]

OK, it's mythbusting time. I heard these three today and went looking for evidence to prove or disprove them. I'm not looking for "In theory it is this but in practice it is different" answers. I am looking for reputable evidence to inform my practice.

I can't base my practice upon tradition, myth or the answers of an internet forum so I am hoping that some on here may know of studies to back up or disprove the following:

1) Palpable pulses correlate to varying blood pressures depending on location. I.e. Radial = >80mmHg, Carotid =>40mmHg
This has been consistently taught throughout my last 4 years at university, is it true?

2) Giving high flow oxygen to COPD patients who are hypoxic and suffering an exacerbation will knock off their respiratory drive?
Todays class was about using nasal prongs first or only 6LPM via Hudson mask. I found information saying that this may be able to happen in theory but the amount it actually occurs makes it statistically insignificant. Any studies out there that give a definite conclusion?

3) Cricoid pressure should be used during intubation to stop regurgitation and ensure a better view of the vocal cords.
I was recently participating in a workshop with an emergency consultant who said that they no longer perform cric pressure as it doesn't work and that, although slow, the rest of medicine is slowly catching up with this concept. Again any evidence?

Um, you shouldn't have a BP cuff on the patient head go be doing a palpable BP by carotid (I'm teasing on this one. )

If anyone needs o2. Give it. I don't care if they have COPD or not. If they are sporting an O2 sat of 80 and their nail beds are blue, they get o2. Hypoxic patitients need o2.

If the medic asks for cricoid pressure, they get it.

 

[Smellypaddler]

Maybe I should have been clearer with myth number 1.

The notion being taught is that if you don't have a BP cuff but can palpate a radial pulse then the pt has a systolic BP >80mmHg.

I agree with your treatment of hypoxic pt's but specifically want some evidence to say that high flow 02 will or will not knock off the resp' drive of a C02 retainer.

My question is "WHY" is the medic asking for the cric pressure? Because of confirmation bias, tradition, routine or evidence? Where is the evidence to say that cric pressure works to prevent regurgitation, aspiration etc?

 

[Carlos Danger]

OK, it's mythbusting time. I heard these three today and went looking for evidence to prove or disprove them. I'm not looking for "In theory it is this but in practice it is different" answers. I am looking for reputable evidence to inform my practice.

I can't base my practice upon tradition, myth or the answers of an internet forum so I am hoping that some on here may know of studies to back up or disprove the following:

1) Palpable pulses correlate to varying blood pressures depending on location. I.e. Radial = >80mmHg, Carotid =>40mmHg
This has been consistently taught throughout my last 4 years at university, is it true?
Lies, all lies.

2) Giving high flow oxygen to COPD patients who are hypoxic and suffering an exacerbation will knock off their respiratory drive?
Todays class was about using nasal prongs first or only 6LPM via Hudson mask. I found information saying that this may be able to happen in theory but the amount it actually occurs makes it statistically insignificant. Any studies out there that give a definite conclusion?
Potentially true, but this is no reason to withhold oxygen from someone who needs it. IF it were to happen, you'd just ventilate.

3) Cricoid pressure should be used during intubation to stop regurgitation and ensure a better view of the vocal cords.
I was recently participating in a workshop with an emergency consultant who said that they no longer perform cric pressure as it doesn't work and that, although slow, the rest of medicine is slowly catching up with this concept. Again any evidence?
There is some I believe, but not strong evidence that cric pressure works to prevent regurgitation. 50% of the time it doesn't even occlude the esophagus, it just displaces it laterally. I don't use it routinely.

Congrats on your commitment to base your practice on evidence rather than just what you've been taught. But is there some reason you haven't found the evidence for/against these things yourself?

 

[Smellypaddler]

Thanks Halothane,

1 & 2 I did search google scholar and the databases I have access to but only turned up opinion pieces on the COPD/02 debate and an article from 2000 on pulse correlation with BP.

Other than that I think I'm either looking in the wrong area or typing in the wrong key words. I'm not after a free hand out as such, I was just hoping someone on here could point me towards some evidence on these things so that I could read up myself in order to be better informed next time I hear bad practice being preached as gospel.

To be honest I have been lazy re: the cric pressure question. I heard the info about it not being useful and haven't bothered to look it up. I will try in the near future to have a look for some info.

 

[Mariemt]

It will always come down to following your protocols whether you agree or not.

 

[chaz90]

It will always come down to following your protocols whether you agree or not.

But how do bad protocols change? We have no room to complain if we don't make an effort to improve.

 

[Carlos Danger]

Thanks Halothane,

1 & 2 I did search google scholar and the databases I have access to but only turned up opinion pieces on the COPD/02 debate and an article from 2000 on pulse correlation with BP.

Other than that I think I'm either looking in the wrong area or typing in the wrong key words. I'm not after a free hand out as such, I was just hoping someone on here could point me towards some evidence on these things so that I could read up myself in order to be better informed next time I hear bad practice being preached as gospel.

To be honest I have been lazy re: the cric pressure question. I heard the info about it not being useful and haven't bothered to look it up. I will try in the near future to have a look for some info.

I didn't mean to imply that you were being lazy or looking for a handout. Just wondered what you'd been doing to find out on your own.

Lit searching can be quite tedious and time consuming, unfortunately, and it takes time to get good at it. If you have access to a library at a medical school or large hospital, ask for help from the librarian and they'll teach you about the different databases and how to use search terms. If you don't have access to that, you can still search Pubmed on your own, you just can't get many of the full-texts.

If you've made a solid effort to find evidence supportive of a practice and haven't found any, it could be that there isn't any, and there's your answer. I'm pretty sure that there is a fair amount on the topic of cric pressure, though, in both the EM and the anesthesia literature.

Remember that it is the responsibility of the intervention to prove itself, not the other way around. Until something is supported by evidence, it is false. Don't ever fall for the "well what evidence do you have that it DOESN'T work?" thing.

What I often do is a general Google search for a topic, and look at whatever articles come up on the topic. Then skim the article and look at the references that are listed in the article or at the end. You'll often find a study or two that you can look up on Pubmed, and once you find that it's often easier to find more.

 

[Mariemt]

But how do bad protocols change? We have no room to complain if we don't make an effort to improve.

You can always be involved with QI development . Introduce new ideas etc, but you can't go on your own because its what you decide or believe. If your state protocol or company has one set in place its up to you to follow until significant evidence based research has changed it.

 

[Medic Tim]

You can always be involved with QI development . Introduce new ideas etc, but you can't go on your own because its what you decide or believe. If your state protocol or company has one set in place its up to you to follow until significant evidence based research has changed it.

EMS in other areas of the world is a bit different than the US. Paramedics there have a lot more training and autonomy. they don't always work under a doctors license. The protocols or treatment guidelines are not hard fast rules in these places. Deviating is the norm and expected as a treatment plan is developed for each pt... they are not lumped into a protocol they may or may not fit into.

That said, there are some progressive services in the US that do give their practitioners a lot of discretion when it comes to treatments and protocols.

 

[Medic Tim]

OK, it's mythbusting time. I heard these three today and went looking for evidence to prove or disprove them. I'm not looking for "In theory it is this but in practice it is different" answers. I am looking for reputable evidence to inform my practice.

I can't base my practice upon tradition, myth or the answers of an internet forum so I am hoping that some on here may know of studies to back up or disprove the following:

1) Palpable pulses correlate to varying blood pressures depending on location. I.e. Radial = >80mmHg, Carotid =>40mmHg
This has been consistently taught throughout my last 4 years at university, is it true?

2) Giving high flow oxygen to COPD patients who are hypoxic and suffering an exacerbation will knock off their respiratory drive?
Todays class was about using nasal prongs first or only 6LPM via Hudson mask. I found information saying that this may be able to happen in theory but the amount it actually occurs makes it statistically insignificant. Any studies out there that give a definite conclusion?

3) Cricoid pressure should be used during intubation to stop regurgitation and ensure a better view of the vocal cords.
I was recently participating in a workshop with an emergency consultant who said that they no longer perform cric pressure as it doesn't work and that, although slow, the rest of medicine is slowly catching up with this concept. Again any evidence?

1) not true at all. Some of the studies are posted on here in different threads. Also from personal experience I have has pt's with a systolic of 100 and no radials and a pt with a systolic of 60 with a nice strong radial.
2) again not always true. There is a very small subset of pt's that this will happen to... these are very sick people and you will not typically run into them pre hospitably. I am a big fan of titration. Again there are several studies around here if you know where to look (I don't or I would have linked them)
3)
I was taught the same thing when I went to school. We are now told to only use it if we need to. personally , someone doing the sellick has never made the difference between me getting the tube or not. again no links... sorry I couldn't help to much.

 

[Sublime]

A quick google search on number 3 revealed these results. I'm sure I could dig up some stuff on the other two but I'll let someone else do the work for those since I am about to do some homework for nursing school.

From Annals of Emergency Medicine:

The evidence supporting the widespread use of cricoid
pressure to prevent aspiration is unconvincing by current
standards of evidence-based medicine

http://felipeairway.sites.medinfo.ufl.edu/files/2009/06/annals-of-emergency-medicine-2007-ellis1.pdf

Anesthesia study on cric. pressure and BURP maneuver:

There is no benefit to routinely applying a modified "BURP" maneuver to the cricoid cartilage during rapid sequence induction of anesthesia.

http://www.unboundmedicine.com/evidence/ub/citation/15625265/The_%22BURP%22_maneuver_worsens_the_glottic_view_when_applied_in_combination_with_cricoid_pressure_

And another from Annals of EM:

Using a cadaver model, we found pressing on the neck during curved blade laryngoscopy greatly affects laryngeal view. Overall, bimanual laryngoscopy improved the view compared to cricoid pressure, BURP, and no manipulation. Cricoid pressure and BURP frequently worsen laryngoscopy. These data suggest bimanual laryngoscopy should be considered when teaching emergency airway management.

http://www.ncbi.nlm.nih.gov/pubmed/16713784

 

[Clipper1]

2) Giving high flow oxygen to COPD patients who are hypoxic and suffering an exacerbation will knock off their respiratory drive?
Todays class was about using nasal prongs first or only 6LPM via Hudson mask. I found information saying that this may be able to happen in theory but the amount it actually occurs makes it statistically insignificant. Any studies out there that give a definite conclusion?

The actual myth here is that you are giving "high flow" oxygen. A non rebreather mask is not a high flow device.

The other misunderstandings rather than using the word myth are the textbook O2 percentages some believe they are giving for oxygen devices. A 6 L NC is not going to give much for an FiO2 if the person is breathing fast and/or taking large tidal volumes.

We now have a better understanding why patient's may go apneic when a higher FiO2 is given and it has very little to do with "hypoxic drive". There are a few other principles which offer a better explanation such as hypoxic pulmonary vasoconstriction, V/Q mismatching and deadspace ventilation. This understanding is why CPAP and BIPAP have become very popular over the past 30+ years.