# Asthma versus CHF V/Q mismatch and ETCO2



## rhan101277 (May 22, 2011)

I have been scowering the internet trying to find some ETC02 waveforms for people with CHF.  Most times I read that the waveforms for CHF or upright a normal but how can that be if the fluid is stopping gas exchange.

I am trying to find a definitive way to tell the difference between folks who have a CHF and asthma hx and have wheezing.  I have had people who had CHF present with pitting edema and SOB and found to have wheezes but also use inhalers for their asthma symptoms.

If they already have pitting edema then it has taken a few days to get that way.  If they have wheezing it should be within reason to believe it is CHF related, since the fluid simply doesn't go away as the kidneys can only filter out so much.

I am trying to get some feedback on how I can better assess these patients who have both asthma and CHF hx.


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## fma08 (May 23, 2011)

rhan101277 said:


> I have been scowering the internet trying to find some ETC02 waveforms for people with CHF.  Most times I read that the waveforms for CHF or upright a normal but how can that be if the fluid is stopping gas exchange.
> 
> I am trying to find a definitive way to tell the difference between folks who have a CHF and asthma hx and have wheezing.  I have had people who had CHF present with pitting edema and SOB and found to have wheezes but also use inhalers for their asthma symptoms.
> 
> ...



As far as I was aware, put simply, wheezing means bronchoconstriction, whether it be from inflammatory processes in asthma, congestion in some sort of respiratory infection, etc. That's what the waveform is picking up, the fact that there is bronchoconstriction. I haven't heard anything about it differentiating between the underlying causes.

Of course, I could be misinformed... It wouldn't be the first time...


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## mycrofft (May 23, 2011)

*Breath sounds*

Wheeze:  "WEEEZE" ( on exhalation). Due to bronchial obstruction causing your greater airways to whistle like a pop bottle, sort of. More like a flute.
WHEEZE on inhalaton is stridor, ususally a foreign object or intrusion of some sort, but it can be a very bad wheeze, not long before things get "ominously quiet"...h34r:
CHF: "Gurgle gurgle gurgle" on inhalation or attempt to exhale.
       Also, "the sound of sand falling on a balloon" (rales) on inhalation, and sometimes on exhalation, which is the sound of alveoli and bronchioles that were glued shut, opening by the negative pressure of inhalation and resultant differential versus ambient air "pop"ing open each one. Usually starts at bases and works way up, but if the room is quiet, and the pt's mouth is wide open, you can hear rales without a scope, assuming your IPOD has not been too loud all these years.
CHF will also show a concurrent change in vitals and maybe heart auscultation. 
No batteries needed, thank you very much. This is a simplification, see your guru.


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## usafmedic45 (May 23, 2011)

> I am trying to find a definitive way to tell the difference between folks who have a CHF and asthma hx and have wheezing.



Non-respiratory symptoms (pedal or sacral edema, JVD, hepatomegaly, etc) are the best ways to do it.  Rely less on technology and assess the patient with your eyes, ears and hands.



> If they already have pitting edema then it has taken a few days to get that way.



Not always.



> I have had people who had CHF present with pitting edema and SOB and found to have wheezes but also use inhalers for their asthma symptoms.



Yeah, the two conditions can coexist.  However- more commonly- the docs hear wheezing and somewhat inappropriately give the patient a bronchodilator.



> Most times I read that the waveforms for CHF or upright a normal but how can that be if the fluid is stopping gas exchange.



It's not totally stopping gas exchange because if it were, the patient would be dead very quickly.  

The only finding that differs from normal is that you might (keep in mind this is a very non-specific finding) see in CHF some narrowing of the ETCO2 waveform due to reduced tidal volumes without restricted airflow.  However, it isn't common and it's not a good way to differentiate.   In asthma on the other hand, you may (again...not always and don't rely on it as a diagnostic finding) see widening of the ETCO2 waveform as the patient's exhalation is prolonged due to the restriction in airflow that is bronchospasm.


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## usalsfyre (May 23, 2011)

rhan101277 said:


> I am trying to get some feedback on how I can better assess these patients who have both asthma and CHF hx.



As USAF noted, history and physical exam, as well as knowing how each condition typically presents and knowing what times of the year your patient populations have their respective exacerbations is the ticket. 

If your looking for a concrete objective finding that distingushes between the two, it doesn't exist. This kinda stuff is where paramedics have to put on the big boy pants and be medical practitioners.


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## MSDeltaFlt (May 23, 2011)

rhan101277 said:


> I have been scowering the internet trying to find some ETC02 waveforms for people with CHF.  Most times I read that the waveforms for CHF or upright a normal but how can that be if the fluid is stopping gas exchange.
> 
> I am trying to find a definitive way to tell the difference between folks who have a CHF and asthma hx and have wheezing.  I have had people who had CHF present with pitting edema and SOB and found to have wheezes but also use inhalers for their asthma symptoms.
> 
> ...



Rhan,  you're in Mississippi, nearly every CHF'er I pick up also has COPD.  And if you use the same protocols as I do, and I think you might, you have to call and ask "Mother May I" in order to give either a neb or lasix.  To differentiate look for JVD, pitting edema, musical wheeze, orthopnea, fever, and try to tell which came first in that pts' particular episode.  You'll need to tell the OLMC if it is either CHF, COPD, pneumonia, or a combination.


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## mycrofft (May 23, 2011)

*You can have both CHF and asthma.*

 In fact, older people with a history of respiratory exposure can and will present with both COPD/asthma and CHF. Maybe some CA/mesothelioma to top the trifecta off.
Sorry if this veered away from learning about the instruments, but old grumps like me hate to see three responders watching a screen while the pt is gasping her/his last.


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## Too Old To Work (May 23, 2011)

usafmedic45 said:


> Non-respiratory symptoms (pedal or sacral edema, JVD, hepatomegaly, etc) are the best ways to do it.  Rely less on technology and assess the patient with your eyes, ears and hands.



What? Are you some kind of radical or something? 



> Yeah, the two conditions can coexist.  However- more commonly- the docs hear wheezing and somewhat inappropriately give the patient a bronchodilator.



A lot of doctors subscribe to the "chicken soup" school of medicine when it comes to Albuterol. Can't hurt, might help. I've just never liked that approach. I think that most medics and many doctors have a hard time, or maybe were not well taught, to differentiate between the two. Wheezing can occur with any kind of restriction, not just Asthma.  I always look for diaphoresis, hypertension, and normal inspiratory to expiratory ratio for CHF. 

The ETCO2 waveform and number can help make the diagnosis, but you still have to look at the patient. Many patients will also tell you what they think it is, especially patients who have both conditions. 

[/QUOTE]
The only finding that differs from normal is that you might (keep in mind this is a very non-specific finding) see in CHF some narrowing of the ETCO2 waveform due to reduced tidal volumes without restricted airflow.  However, it isn't common and it's not a good way to differentiate.   In asthma on the other hand, you may (again...not always and don't rely on it as a diagnostic finding) see widening of the ETCO2 waveform as the patient's exhalation is prolonged due to the restriction in airflow that is bronchospasm.[/QUOTE]


I've noticed a trend towards a square, short, and rapidly repeated wave form with CHF. It's not anything I'd hang a treatment plan on, but it does seem to be characteristic.


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## mycrofft (May 23, 2011)

*Albuteral is like mother's milk. Hahaha.*

Try albuteral with CHF, or atrial fib.


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## rhan101277 (May 24, 2011)

MSDeltaFlt said:


> Rhan,  you're in Mississippi, nearly every CHF'er I pick up also has COPD.  And if you use the same protocols as I do, and I think you might, you have to call and ask "Mother May I" in order to give either a neb or lasix.  To differentiate look for JVD, pitting edema, musical wheeze, orthopnea, fever, and try to tell which came first in that pts' particular episode.  You'll need to tell the OLMC if it is either CHF, COPD, pneumonia, or a combination.



I'm in Louisiana now and we don't have to call.  If you are in doubt about the cause of respiratory distress then you need to call OLMC.  We can however give lasix 40mg IVP under standing orders.  We can give twice the home dose if pt. takes it up to 100mg/max.


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## MSDeltaFlt (May 24, 2011)

rhan101277 said:


> I'm in Louisiana now and we don't have to call.  If you are in doubt about the cause of respiratory distress then you need to call OLMC.  We can however give lasix 40mg IVP under standing orders.  We can give twice the home dose if pt. takes it up to 100mg/max.



Good for you on getting out of the medical dark ages.


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## jroyster06 (May 24, 2011)

I see people on here talking about lasix alot. I have been taught as well as done lots of research and have found that Lasix is only indicated about 50% of the time. Just because there is pitting edema, doesnt mean they are fluid overloaded. The fluid just may not be in the correct spot. We have a ton of chf's here and i can say I have never given lasix. I have had great luck treating chf with cpap/nitro paste. (were getting pumps soon for nitro drips)


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## jroyster06 (May 24, 2011)

As for your originall question, maybe this link will shed some light. Its a little lengthy but works great for easy explanation of ETCO2.

http://emscapnography.blogspot.com/


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## usafmedic45 (May 25, 2011)

> Are you some kind of radical or something?



Yup.


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