# Thoughts on using pulse ox for BP?



## bunkie (Dec 17, 2009)

http://www.ems1.com/ems-products/co-screening/articles/680842-The-Other-Side-of-Pulse-Oximetry/



> One easy way to palpate a blood pressure is to place the pulse oximeter probe on a digit in the extremity in which you're taking a blood pressure. Wait for a steady waveform and decent saturation reading, then inflate your BP cuff.
> 
> Watch the numbers as the waveform disappears, and when it reappears during deflation. Those numbers are roughly equivalent to the systolic blood pressure reading you'd obtain during conventional palpation of a blood pressure.



I was reading some articles and read over this. Any thoughts on this?


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## reaper (Dec 17, 2009)

Considering that is takes longer for the SPO2 to react to the change, there is no way to get an accurate reading this way.

Is it that hard to take a real BP or at least feel for a pulse?


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## vquintessence (Dec 17, 2009)

bunkie said:


> http://www.ems1.com/ems-products/co-screening/articles/680842-The-Other-Side-of-Pulse-Oximetry/
> 
> 
> 
> I was reading some articles and read over this. Any thoughts on this?



I would think it'd be faster getting the BP by palpation, instead of relying on a piece of equipment that typically underperforms from many different factors.

Training your hands for sensitivity will reap more benefits than relying on an additional gadget to do a task it was not intended for.

On the other hand... I've never seen this done before.


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## bunkie (Dec 17, 2009)

reaper said:


> Considering that is takes longer for the SPO2 to react to the change, there is no way to get an accurate reading this way.
> 
> Is it that hard to take a real BP or at least feel for a pulse?



I didn't think so. But I considered the fact that maybe the writer of the article came up with it as a solution to not being able to hear over road noise? I was just wondering about it. I do fine with good old fashioned bp's.


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## VentMedic (Dec 17, 2009)

I can not believe this guy posted something like that.  All he would have to do is visit any ICU where a patient has a manual BP cuff, arterial line and pulse ox to notice the discrepancies.


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## CAOX3 (Dec 17, 2009)

Roughly equivalent?


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## VentMedic (Dec 17, 2009)

CAOX3 said:


> Roughly equivalent?


 

If you are treating a patient, do you want to defend "roughly equivalent"? 

Would you have the backing of the pulse ox manufacturer for this use?


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## 18G (Dec 17, 2009)

I read this technique(if u want to call it that) a while back and tried it just to see how well it worked... yep... didn't work well at all. I would never recommend this.  

I really dont see any advantage of using the pulse ox to try and obtain a blood pressure. If you can't feel a radial pulse chances are the pulse ox isn't going to detect pulsation either.


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## Lifeguards For Life (Dec 17, 2009)

VentMedic said:


> I can not believe this guy posted something like that.  All he would have to do is visit any ICU where a patient has a manual BP cuff, arterial line and pulse ox to notice the discrepancies.



steven "kelly" Grayson does it again.

The same man who brought us the modified scrotal lead!

Reporting that a practitioner was unable to palpate a blood pressure due to weak pulse, vehicle movement or any other condition is preferable to using a technique that is wrought with inaccurate and unreliable readings and is frequently difficult to use. As a profession I think that inventing ways, that are unreliable and unproven, are in the past. EMS personnel treat 'tricks of the trade' as something to be proud of. We should look at what we do as a profession with an eye toward performing what has been proven not what may seem 'cool' and trendy. If you believe that the use of a pulse oxymeter provides an indication of blood flow to an extremity prove it empirically. You may be instrumental in taking away the image of EMS as being 'cowboys' and move towards it being a profession.


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## CAOX3 (Dec 17, 2009)

VentMedic said:


> If you are treating a patient, do you want to defend "roughly equivalent"?
> 
> Would you have the backing of the pulse ox manufacturer for this use?



I suggest you use a pulse ox to obtain a pulse oximetry and a blood pressure cuff to obtain a blood pressure.  Are these two procedures so time consuming for some that we need little tricks to save a few seconds.


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## DigitalSoCal (Dec 17, 2009)

A largely flawed solution to a problem that doesn't exist


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## VentMedic (Dec 17, 2009)

CAOX3 said:


> I suggest you use a pulse ox to obtain a pulse oximetry and a blood pressure cuff to obtain a blood pressure. Are these two procedures so time consuming for some that we need little tricks to save a few seconds.


 
Did you read my post?

I do NOT recommend using this method.


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## VentMedic (Dec 18, 2009)

Lifeguards For Life said:


> steven "kelly" Grayson does it again.
> 
> The same man who brought us the modified scrotal lead!


 
He uses the letters "CCEMT-P" after his name.

I wonder if he titrates pressors like Levophed using this method.


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## EMSLaw (Dec 18, 2009)

I don't trust a field pulse ox to measure accurately even that which it's intended to measure.  I'll stick to using a stethoscope to get blood pressures.  

If you're going to do this, you might as well just watch your BP cuff and note when the needle starts bouncing with the pulse.  

And no, I don't recommend that method either, I hasten to add.


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## VentMedic (Dec 18, 2009)

One has to consider that each pulse ox brand is different.  Right now Masimo is considered one of the best for its motion filtering technology. However, there is still much research to be done with the sensitivity and uses for the perfusion index.  Right now the majority of their PI research is for neonates.  

 We did switch to Masimo and it took a significant amount of our budget to do so.


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## Melclin (Dec 18, 2009)

VentMedic said:


> One has to consider that each pulse ox brand is different.  Right now Masimo is considered one of the best for its motion filtering technology. However, there is still much research to be done with the sensitivity and uses for the perfusion index.  Right now the majority of their PI research is for neonates.
> 
> We did switch to Masimo and it took a significant amount of our budget to do so.



Is there a relationship between PI and PPG as measured by pulse ox? I've seen PPG mentioned in a Crit-care book, but I've not come across PI much...although I know almost nothing about both, but it seems on brief inspection that the two readings might be based on similar data. I understand that PI is a relative measurement of pulse strength and that PPG is volumetric, or change in volume, but it seems like that is basically the same way of expressing the same information..

Is there a reason why we can't simply press a 'mode' button and switch our pulse oxs to take these readings, other than just the fact that the feature wasn't previously added? 

Would these readings be of any value in the prehospital setting (what, briefly, is the clinical application of the two values)?


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## VentMedic (Dec 18, 2009)

Melclin said:


> I understand that PI is a relative measurement of pulse strength and that PPG is volumetric, or change in volume, but it seems like that is basically the same way of expressing the same information..
> 
> Is there a reason why we can't simply press a 'mode' button and switch our pulse oxs to take these readings, other than just the fact that the feature wasn't previously added?
> 
> Would these readings be of any value in the prehospital setting (what, briefly, is the clinical application of the two values)?


 
Terms:
PPG: Pulsatile Photoplethysmographic 

PI: Perfusion Index 

Some of these factors would also depend on the algorithm used for the PPG amplitude. I've got to admit this is getting into a technical area where I may not be able to adequately explain it or even begin to explain it. 

Masimo can change it algorithm with the more sophisticated models to adapt in low perfusion and can give an indication for the PI and the wavelengths. 

The issue would be would the PPG and algorithm be appropriate for motion and skin considerations to adequately monitor PI. Motion is probably the biggest issue in prehospital as many of the situations studied were in controlled OR or ICU environments. Neonates has also been relatively easy to study due to their skin density. Masimo has some good articles from their studies on their website. 

PI
http://www.masimo.com/Rainbow/pdf/LAB3410F%20-%20PI.pdf

PVI (masimo's own term)
http://www.masimo.com/pvi/index.htm


A decent article although it doesn't get into great detail for the technical aspect.
http://www.rtmagazine.com/issues/articles/2002-08_03.asp


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## redcrossemt (Dec 18, 2009)

VentMedic said:


> He uses the letters "CCEMT-P" after his name.
> 
> I wonder if he titrates pressors like Levophed using this method.



That's a good idea! I never thought the pulse ox had so many uses!


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## MSDeltaFlt (Dec 19, 2009)

bunkie said:


> http://www.ems1.com/ems-products/co-screening/articles/680842-The-Other-Side-of-Pulse-Oximetry/
> 
> 
> 
> I was reading some articles and read over this. Any thoughts on this?


 
You have got to be kidding me. I don't see why you would want to palpate at all in the first place. The Good Lord gave us two good ears, a stethescope, and a BP cuff for a reason. Auscultate. I don't like palpated blood pressures.

Short cuts are are only halfway doing doing something.  Halfway also means half-arsed.

Just my opinion.


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## boingo (Dec 19, 2009)

There was a mention of this exact technique in a recent text on transport medicine, I can't recall the title, its at home, remember reading it while preparing for the FP-C exam.

Air and Surface Patient Transport: Principles and Practice.


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## VentMedic (Dec 19, 2009)

boingo said:


> There was a mention of this exact technique in a recent text on transport medicine, I can't recall the title, its at home, remember reading it while preparing for the FP-C exam.
> 
> Air and Surface Patient Transport: Principles and Practice.


 
The arterial line and its waveform have been mentioned in some CC classes. If there are problems with BP management, we (RRT, RN) will insert an A-Line before flight. If we are having that much problem with pulses and BP, the pulse ox will be of little use.   Also, if a person is on pressors, such as they commonly are on CCT and Flight, the peripherial vasoconstriction will also skew the ability of the pulse ox.  For these patients we will use a earlobe probe which will be of no use for BPs either. 

However, if anyone has ever been in an ICU to observe an A-line wave, pulse ox pleth and a manual BP, you will see the variation.


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## VentMedic (Dec 19, 2009)

It also looks like Grayson has been doing some defending and clarifying of his article in the comments section below the article. I'm sure he's probably on a couple of other EMS forums as well defending it.


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## Ambulance_Driver (Dec 19, 2009)

*Defending the practice in other forums?*

Nah, not really. I was given an assignment to do some "out of the box" thinking on clinical treatment tips. For the first three topics, I chose auscultatory percussion of long bone fractures, assessing tactile vocal fremitus, and alternative uses of pulse oximetry. 

First, I think the pulse oximeter is a vastly misused piece of equipment, and secondly, I think there are other ways to utilize it, with the caveat that you shouldn't place absolute faith in the results you get. At best, it's a stopgap measure, a trick you try when nothing else works. I thought the article had made that clear, but apparently not.

I enjoy the discussions, actually. You guys are pointing out some flaws in my reasoning, and I appreciate that. That's what the comments section after the post is for, as well as discussion forums like this one. 

On the other hand, let me offer a few clarifications:

1. The consensus seems to be that I recommend this trick for everyday use. I don't. I try it when I can't auscultate or palpate one conventionally. It's pretty rare that I can't palpate a pulse when the plethysmograph gets a good tracing, but it *has* happened. 

2. I don't walk into an ER and confidently state, "The patient's BP is XX systolic," when I've done this. Instead, I do what I usually do when I can't obtain a decent BP, which is to say, "I could palpate or auscultate a BP (due to whatever reason), but I did manage to get one number this way (by the method described)."

To my mind, that's better than saying, "Couldn't get a BP," although I'm not shy about saying just that. Sometimes you simply can't. Heck, there have been times when I've said, "Blood pressure? Hell, I'm still working on airway!"

3. My ears suck, from childhood trauma and two tympanoplasties to years of shooting without ear protection, I have measurable deficits through all frequency ranges in both ears, but more so on the left. As a result, I'm one of those stethoscope snobs who has to carry his own high dollar scope, and guards it with his life. The other thing that necessitates is that I auscultate my blood pressures on scene, because road noise makes it almost impossible to hear in my sickest patients. 

So yeah, once I'm in the rig, I palpate pressures a good bit, or use the NIBP. I always figured it went without saying that I auscultated a pressure with my own ears (or a partner I trusted), before I used either of those methods. 

It's all good in theory to advise someone to never palpate a blood pressure, or if you do, "train your fingers to be more sensitive," but that breaks down in real life. When you can't hear for whatever reason, you palpate a blood pressure. And if you've never unsuccessfully tried to feel a radial pulse in a patient you *knew* had one, my hat's off to you, because either you haven't been working on a rig long, or your fingers are more sensitive than mine. If the latter is the case, a career as a concert violinist might make you more money than a medic. You're wasting your talents here. 

4. When I'm titrating pressors, I prefer to have an art line. But since the docs sending those patients have this nasty habit of not bowing to my wishes every time, I frequently transport them without one. When that happens, refer to point #3. And when I get a NIBP reading that doesn't fit the trend or seems grossly wrong, also refer to #3. If necessary, I'll have my partner pull the rig over so that I can get a decent shot at auscultating a pressure. In other words, I use whatever works.

5. The modified scrotal lead remains an excellent trick to play on rookies. Try it some time!


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## Melclin (Dec 20, 2009)

Ambulance_Driver said:


> 1. The consensus seems to be that I recommend this trick for everyday use. I don't...



Well that certainly needs to be clarified. I didn't read it that way, and it seems like plenty of other people didn't either.


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## Ambulance_Driver (Dec 20, 2009)

_
Well,that certainly needs to be clarified. I didn't read it that way, and it seems like plenty of other people didn't either._ 

You know, I was going to post a direct quote from the article to refute that, but...

... I can't find it. Even worse, I can't blame it on editing, because it doesn't read that way in the original version either. So you're right, I didn't make that clear.

Thanks for pointing that out.


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## Melclin (Dec 20, 2009)

Ambulance_Driver said:


> _
> Well,that certainly needs to be clarified. I didn't read it that way, and it seems like plenty of other people didn't either._
> 
> You know, I was going to post a direct quote from the article to refute that, but...
> ...



Waaaaait....an experienced medic politely acknowledging curt but constructive criticism from a student...whats your angle?...is it world domination?...its world domination isn't it.


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## Ambulance_Driver (Dec 20, 2009)

ROFLMAO...

I have my moments. When my legion of flying monkeys completes my quest for world domination, I'll make sure you are on the protected rolls.


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## Tincanfireman (Dec 20, 2009)

Welcome to EMTLife, by the way...


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## Lifeguards For Life (Dec 20, 2009)

Ambulance_Driver said:


> ROFLMAO...
> 
> I have my moments. When my legion of flying monkeys completes my quest for world domination, I'll make sure you are on the protected rolls.



welcome Supermedic!


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