# End tidal CO2 questions



## ParamedicStudent (Oct 18, 2016)

I have a couple questions about EtCO2:

Let's talk about patients with COPD/Asthma. I know they retain CO2 due to physical damage to tissues, so that does that mean that their end tidal CO2 would be low on the monitor, because they're holding back CO2 and not all of it is being released out when they exhale? How about when they're having an exacerbation? Is it the same logic?

How about in the case of DKA? A diabetic patient with DKA has too much sugar in their bloodstream, and that causes them to have metabolic acidosis. They usually have Kussmaul's respirations. They're trying to change their metabolic acidosis to respiratory acidosis to try to blow off their CO2, but is that possible? Will their EtCO2 be higher because they're blowing off CO2? Or will it be lower because they are hyperventilating?


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## VentMonkey (Oct 18, 2016)

ParamedicStudent said:


> I have a couple questions about EtCO2:
> 
> Let's talk about patients with COPD/Asthma. I know they retain CO2 due to physical damage to tissues, so that does that mean that their end tidal CO2 would be low on the monitor, because they're holding back CO2 and not all of it is being released out when they exhale? How about when they're having an exacerbation? Is it the same logic?


Their (COPD) ETCO2 would be higher because they're _retaining _carbon dioxide. These folks often live in 60's. As far as their exacerbation, I would think an increase in their ETCO2 coupled with increasing muscle fatigue, lethargy, and an increased PaCO2, and PaO2 (done via ABG at the hospital once they fail less invasive therapies) is highly indicative of respiratory failure.



ParamedicStudent said:


> How about in the case of DKA? A diabetic patient with DKA has too much sugar in their bloodstream, and that causes them to have metabolic acidosis. They usually have Kussmaul's respirations. They're trying to change their metabolic acidosis to respiratory acidosis to try to blow off their CO2, but is that possible? Will their EtCO2 be higher because they're blowing off CO2? Or will it be lower because they are hyperventilating?


It's not the sugar. The ketones being a cellular  waste product of the hyperglycemia is what's creating this metabolic acidosis, and in turn, and elevated (Kussmaul's) respiratory pattern.

This is a protective mechanism to rid the body of this waste product. The causes a respiratory _alkalosis_ as they're compensating, again, with an increased respiratory drive. If the problem is not corrected (hyperglycemia is the problem not the respiratory rate; they need tons of fluids and Insulin), then certainly they can stop breathing, or under breathe/ hypoventilate causing respiratory acidosis.

Op, it sounds to me like you're genuinely confused. Hopefully this helps a little. Here's a decent article that breaks it down better than me:

http://www.paramedicine.com/pmc/End_Tidal_CO2.html


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## RRTMedic (Nov 6, 2016)

ParamedicStudent said:


> I know they retain CO2 due to physical damage to tissues, so that does that mean that their end tidal CO2 would be low on the monitor, because they're holding back CO2 and not all of it is being released out when they exhale?



So ETCO2 is a _correlation _to PaCO2, not necessarily an accurate picture of the partial arterial pressure of carbon dioxide. Actually, in *normal* lungs, ETCO2 reads approximately 5 mmHg _lower_ that PaCO2. However, your question regards the retention of CO2... I'll see if I can give you an illustration for ETCO2 vs PaCO2. 

Our lungs contain areas that do not ventilate well... whether this be a perfusion problem or a ventilation problem. Take for instance a patient having a pulmonary embolism; this patient is not moving blood well to the lungs for gas exchange, meaning that the CO2 would not be exhaled, meaning your ETCO2 would be.... LOW. Poor perfusion, right? 

On the same token, lets say that same area of lungs that aren't performing gas exchange well has GREAT blood perfusion to the alveoli, but the alveoli are not being ventilated due to pulmonary edema or say pneumonia. Then gas exchange can't occur because there is a physical barrier there. The CO2 builds in the blood, but the ETCO2 would read LOW because that area of the lung isn't being ventilated.

*Just remember, ETCO2 is a great tool, but you have to understand the physiological concepts. ETCO2 most closely matches PaCO2 in patients with NORMAL lungs, but not so much with patients who have chronic respiratory conditions (ie COPD). If you want a more in depth look at the physiology, check out the terms "Deadspace" and "Shunt" (or "V/Q Mismatch"). Little difficult to grasp at first, but will widen your perspective of pulmonary maladies.*



ParamedicStudent said:


> How about in the case of DKA? A diabetic patient with DKA has too much sugar in their bloodstream, and that causes them to have metabolic acidosis. They usually have Kussmaul's respirations. They're trying to change their metabolic acidosis to respiratory acidosis to try to blow off their CO2, but is that possible? Will their EtCO2 be higher because they're blowing off CO2? Or will it be lower because they are hyperventilating?



So in the case of DKA, the body is most definitely in a metabolic acidosis because there is an excess of ketones from fat breakdown (for the sake of this discussion, ketones = acid). When ketones are present, what buffers them? That's right, sodium bicarbonate. The ketones combine with the sodium bicarb, effectively lowering the bicarbonate level, which will drop the blood pH. To compensate, the respiratory rate picks up to try and blow off CO2 (which also = acid) in a nature response to try and normalize pH (which rarely happens in a metabolic acidosis). 

When considering ETCO2, it is likely that the ETCO2 will be lower due to hyperventilation. BUT, it's a cool and reliable way to trend your respiratory rate. Just remember, these patients may LOOK bad respiratory wise, but they DO NOT need ventilatory support unless failure is imminent. They are a NIGHTMARE to manage on a ventilator. Aggressive fluid resuscitation, insulin, and treatment of hyperkalemia goes a long way.


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## VentMonkey (Nov 6, 2016)

RRTMedic said:


> When considering ETCO2, it is likely that the ETCO2 will be lower due to hyperventilation. BUT, it's a cool and reliable way to trend your respiratory rate. Just remember, these patients may LOOK bad respiratory wise, but they DO NOT need ventilatory support unless failure is imminent. They are a NIGHTMARE to manage on a ventilator. Aggressive fluid resuscitation, insulin, and treatment of hyperkalemia goes a long way.


Not sure where you were going with the rest of your post, but this is 100% on point. Also, understanding a simple tool like "Winter's Formula" may actually go a long way if you do find yourself having to manage their airway post haste. Meeting their metabolic demands, and understanding why these patients must stay acidotic isn't something most prehospital providers may (initially) understand, but at the very least understand at this stage in the game their current metabolic state must be matched for, well, lack of a better word, survival. Decent post overall, welcome to the forum @RRTMedic.


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## RRTMedic (Nov 6, 2016)

VentMonkey said:


> Decent post overall, welcome to the forum



Thanks... I find myself at a remote/slow base staring at the wall haha. What better to do than put my thoughts on a forum?


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## VentMonkey (Nov 6, 2016)

RRTMedic said:


> Thanks... I find myself at a remote/slow base staring at the wall haha. What better to do than put my thoughts on a forum?


NP, feel free to peruse the HEMS section, I'm always promoting that section of this forum, haha.


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## Tigger (Nov 6, 2016)

http://www.medicscribe.com/capnography/

I still find myself confused and I find this to be a decent primer.

Had a DKA patient the other night, respiratory rate of 44 and EtCO2 of 6. Initially that didn't make sense to me, the patient is acidotic right? Metabolically yes, but your end tidal is reading the compensatory hypocapnia/alkalosis.


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## RRTMedic (Nov 6, 2016)

Tigger said:


> Initially that didn't make sense to me, the patient is acidotic right? Metabolically yes, but your end tidal is reading the compensatory hypocapnia/alkalosis



You're absolutely right. These patients are acidotic. The low ETCO2 is most definitely due to the hyperventilatory compensation that is occurring.

An ABG may look something like this: pH 7.29 / PaCO2 25 / PaO2 89 / HCO3- 10

Just remember that the acidosis is due to the LOW bicarb... because the bicarb has essentially been "ate up" by the ketonic acids


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## Tigger (Nov 6, 2016)

RRTMedic said:


> You're absolutely right. These patients are acidotic. The low ETCO2 is most definitely due to the hyperventilatory compensation that is occurring.
> 
> An ABG may look something like this: pH 7.29 / PaCO2 25 / PaO2 89 / HCO3- 10
> 
> Just remember that the acidosis is due to the LOW bicarb... because the bicarb has essentially been "ate up" by the ketonic acids


Incidentally the pH was 6.96...yikes.


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## VentMonkey (Nov 6, 2016)

Tigger said:


> http://www.medicscribe.com/capnography/
> 
> I still find myself confused and I find this to be a decent primer.
> 
> Had a DKA patient the other night, respiratory rate of 44 and EtCO2 of 6. Initially that didn't make sense to me, the patient is acidotic right? Metabolically yes, but your end tidal is reading the compensatory hypocapnia/alkalosis.


http://fitsweb.uchc.edu/student/sel...ompensatory_responses_metabolic_acidosis.html

Here's a quick tutorial on Winter's Formula, but basically the thought process is to "match" their CO2 number to what their most recent ABG reflected if the patient's airway is being managed via mechanical ventilations. Bringing their ETCO2, and moreover, their PaCO2 within "normal" limits can be detrimental, as the primary cause for their drop in PaCO2 is metabolic in nature, hence the reason, aggressive IVF, and insulin is indicated until their pH can restored WNL, and extubated; make sense, I hope?...


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## Tigger (Nov 6, 2016)

VentMonkey said:


> http://fitsweb.uchc.edu/student/sel...ompensatory_responses_metabolic_acidosis.html
> 
> Here's a quick tutorial on Winter's Formula, but basically the thought process is to "match" their CO2 number to what their most recent ABG reflected if the patient's airway is being managed via mechanical ventilations. Bringing their ETCO2, and moreover, their PaCO2 within "normal" limits can be detrimental, as the primary cause for their drop in PaCO2 is metabolic in nature, hence the reason, aggressive IVF, and insulin is indicated until their pH can restored WNL, and extubated; make sense, I hope?...


It does.

I was concerned that I was going to have to intubate this patient and that prospect did not excite me. He was exhausted (tachypneic for three days) and fairly altered. At one point his work of breathing increased significantly and he became significantly altered, fortunately some positioning and an NRB seemed to right the ship. 

But having to ventilate him seemed awful...I need that compensation to stave off further metabolic issues and trying to match that with mechanical ventilation sounded...difficult.


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## RRTMedic (Nov 6, 2016)

VentMonkey said:


> http://fitsweb.uchc.edu/student/sel...ompensatory_responses_metabolic_acidosis.html
> 
> Here's a quick tutorial on Winter's Formula, but basically the thought process is to "match" their CO2 number to what their most recent ABG reflected if the patient's airway is being managed via mechanical ventilations. Bringing their ETCO2, and moreover, their PaCO2 within "normal" limits can be detrimental, as the primary cause for their drop in PaCO2 is metabolic in nature, hence the reason, aggressive IVF, and insulin is indicated until their pH can restored WNL, and extubated; make sense, I hope?...



This is definitely off-topic to the original post... but I have found these patients (who are on mechanical ventilation) are usually best placed in a spontaneous, pressure supported mode (which may be PS/CPAP or just SIMV with an extremely low rate). It has been my experience that their respiratory drive is so strong that trying to use an Assist/control mode results in dyssynchrony and obvious discomfort. I may be wrong, but they sure do look much better when you just let them do their thing on their own.

I typically find this approach at 3 AM to be most useful to your TBI patient "neurostorming" as well


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## VentMonkey (Nov 6, 2016)

Tigger said:


> It does.
> 
> I was concerned that I was going to have to intubate this patient and that prospect did not excite me. He was exhausted (tachypneic for three days) and fairly altered. At one point his work of breathing increased significantly and he became significantly altered, fortunately some positioning and an NRB seemed to right the ship.
> 
> But having to ventilate him seemed awful...I need that compensation to stave off further metabolic issues and trying to match that with mechanical ventilation sounded...difficult.


Yeah, IMO, unless they have to absolutely positively be intubated in the field, there's no reason to. If you do need to though, try and grab the most current set of ABG's, and/ or have respiratory draw a set, figure out the formula, and match the minute ventilation best you can to meet the ETCO2 closest to their most recent/ current PaCo2. This type of patient is the quintessential patient that displays the importance of prehospital ventilator management. They *should not* be BVM-d.

Side note: glad to see I have a fellow respiratory nerd in @RRTMedic.


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## Tigger (Nov 6, 2016)

VentMonkey said:


> Yeah, IMO, unless they have to absolutely positively be intubated in the field, there's no reason to. If you do need to though, try and grab the most current set of ABG's, and/ or have respiratory draw a set, figure out the formula, and match the minute ventilation best you can to meet the ETCO2 closest to their most recent/ current PaCo2. This type of patient is the quintessential patient that displays the importance of prehospital ventilator management. They *should not* be BVM-d.
> 
> Side note: glad to see I have a fellow respiratory nerd in @RRTMedic.


This was a 911 call so if we ended up intubating I am not sure what we would have done. Certainly not shooting for the usual 35-45 range, but really it be anyone's guess.

We have an IStat but it's for the community paramedic program right now.


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## VentMonkey (Nov 6, 2016)

Tigger said:


> This was a 911 call so if we ended up intubating I am not sure what we would have done. Certainly not shooting for the usual 35-45 range, but really it be anyone's guess.
> 
> We have an IStat but it's for the community paramedic program right now.


What kind of vents does your service carry? I always advocate learning that bad boy so when that "just in case" patient presents, it's use is not in question.


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## Tigger (Nov 6, 2016)

VentMonkey said:


> What kind of vents does your service carry? I always advocate learning that bad boy so when that "just in case" patient presents, it's use is not in question.


PneuPac Parapac. Pretty limited options wise. We do have PEEP valves on the circuits in addition to the actual vent's settings.


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## VentMonkey (Nov 6, 2016)

Tigger said:


> PneuPac Parapac. Pretty limited options wise. We do have PEEP valves on the circuits in addition to the actual vent's settings.


Right on, fair enough. If I am not mistaken that model is somewhere between an AutoVent, and an actual ventilator. Still, It's better than a BVM, which our ground/ 911 ops carry only.


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## StCEMT (Nov 7, 2016)

Tigger said:


> PneuPac Parapac. Pretty limited options wise. We do have PEEP valves on the circuits in addition to the actual vent's settings.


I've got the same, I really wish we carried something a bit better. Like Vent said, better than a BVM, but it is a step down from what I was taught vent operations on.


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## Tigger (Nov 7, 2016)

VentMonkey said:


> Right on, fair enough. If I am not mistaken that model is somewhere between an AutoVent, and an actual ventilator. Still, It's better than a BVM, which our ground/ 911 ops carry only.


Pretty much. Less mickey mouse than auto/surevent but not exactly customizable.


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## RRTMedic (Nov 7, 2016)

VentMonkey said:


> Right on, fair enough. If I am not mistaken that model is somewhere between an AutoVent, and an actual ventilator. Still, It's better than a BVM, which our ground/ 911 ops carry only.



Here in NC we carry Newport HT70 for interfacility transports. Pretty bulky but does give more options that ATVs. I can do AC, SIMC, VC, PC, and PS...switch it to NIV and do CPAP/BiPAP. Can even do a descending ramp on my flow rate. Cool stuff... fairly cheap ~$9000


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## VentMonkey (Nov 7, 2016)

We're a Drager family at our service, but actually in the process of getting new vents.


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## Handsome Robb (Nov 11, 2016)

Tigger said:


> Incidentally the pH was 6.96...yikes.











Sent from my iPhone using Tapatalk


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## medichopeful (Nov 15, 2016)

Here's an excellent lecture on EtCO2 that might answer some of your questions, or at the very least help dispel some myths.

http://emcrit.org/podcasts/etco2-podcast/


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## medichopeful (Nov 15, 2016)

Tigger said:


> It does.
> 
> I was concerned that I was going to have to intubate this patient and that prospect did not excite me. He was exhausted (tachypneic for three days) and fairly altered. At one point his work of breathing increased significantly and he became significantly altered, fortunately some positioning and an NRB seemed to right the ship.
> 
> But having to ventilate him seemed awful...I need that compensation to stave off further metabolic issues and trying to match that with mechanical ventilation sounded...difficult.



Here's an interesting podcast from EMCrit on basically this exact scenario.  Of course, it would be almost impossible to do this in the field, but you might find it interesting:

http://emcrit.org/podcasts/tube-severe-acidosis/


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## VentMonkey (Nov 15, 2016)

Excellent podcast @medichopeful, Doc Weingart never disappoints. Kind of back to my original post, and something I think worth reiterating is that DKA is a _*form*_ of metabolic acidosis. I think in the prehospital setting oftentimes we are so caught up in DKA=Kussmaul breathing; in all actuality it is caused by *any form* of metabolic acidosis, and at this stage in the game these patients are very sick. I think this is worth bringing up because if you do come across a severe sepsis, or toxic OD with a metabolic compensatory component that may need intubation, they will need to be treated the same as though it was a severe DKA with impending respiratory failure. He mentions it in the podcast in reference to severe ASA toxicity, but here's a quick Merck manual link about it:

https://www.merckmanuals.com/profes...e-regulation-and-disorders/metabolic-acidosis

Again, these patients are extremely sick. An excellent takeaway from this podcast for me was, that while ETCO2 may be a poor indicator of how high the patients actual PaCO2 may be, at the very least you will known where the baseline is.

Something @RRTMedic mentioned earlier was his recommendation for ventilator settings on these patients. Something I think that should be pointed out about vent management (again, I am no RT/ RCP) is that there are so many different takes on proper vent settings for specific patient types. Dr. Weingart makes mention of initially matching the patients respiratory rate. I know @Tigger had brought up a concern about how he would have managed this patient had they required intubation.

If it was me I would think I would carefully count an initial (spontaneous) rate, which optimally would be backed by the in-line ETCO2 (it's recorded, and can be proven for starters), once intubated I would then match the rate to the patient's intrinsic rate/ETCO2 reading pre-RSI, and then pass this along to the hospital. I don't think I would be against keeping these patients paralyzed for the transport as chances are they're in an impending respiratory failure to begin with, so my vent setting would be along the lines of A/C, or even CMV if truly paralyzed, and not just properly sedated with f- initial/ intrinsic rate (f), Vt-4-6 ml/ kg IBW, FiO2 @1.0, and optional Peep @ 5. My vent adjustments would focus on the patient's MV to ensure their ETCO2/ rate again, match what they were at initially before intubating them. The standard bilateral IV's probably goes without saying here, but those as well as Sodium Bicarb would be pretty close to where we could reach it.

Again, severe metabolic acidosis regardless of the etiology yields a very complex management approach in the prehospital setting, and ever there was a time, patient, and place to prove our worth as medical providers this would be it.


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## VFlutter (Nov 15, 2016)

Tigger said:


> PneuPac Parapac. Pretty limited options wise. We do have PEEP valves on the circuits in addition to the actual vent's settings.



We used those for our MRI and transport vents in the hospital. I hated them, especially for sick patients. We have the Revel on the helicopter.


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## VentMonkey (Nov 15, 2016)

Chase said:


> We have the Revel on the helicopter.


I think this is an Air Methods favorite. It seems their service here also carries them. I'm keeping my fingers crossed we get the Hamilton as our next vent.


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## VFlutter (Nov 15, 2016)

VentMonkey said:


> I think this is an Air Methods favorite. It seems their service here also carries them. I'm keeping my fingers crossed we get the Hamilton as our next vent.



Ya I think all Air Methods programs are phasing out the LTVs and going with Revels. The Hamilton looks awesome.


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## VentMonkey (Nov 15, 2016)

Chase said:


> Ya I think all Air Methods programs are phasing out the LTVs and going with Revels. The Hamilton looks awesome.


Yeah, a bit tricky to fit in our 407, but we'd make it work. AirLife? Denver has one in theirs, and I agree, it is an awesome vent. I got to toy with the demo they had left a while back and TMK if we get one, the rep will run all of us through the training directly (fingers crossed).


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## StCEMT (Nov 15, 2016)

Chase said:


> We used those for our MRI and transport vents in the hospital. I hated them, especially for sick patients. We have the Revel on the helicopter.


I learned vent basics on the revel. Never really got to use it personally, but I liked what I saw.


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## VentMonkey (Nov 15, 2016)

StCEMT said:


> I learned vent basics on the revel. Never really got to use it personally, but I liked what I saw.


I liked that it had PRVC, but was a tad disappointed otherwise it was the LTV. 

I wished they'd made the screen better with the ability to see flow graphs such as airway pressures etc. (can't always hear them in the aircraft).


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## StCEMT (Nov 15, 2016)

VentMonkey said:


> I liked that it had PRVC, but was a tad disappointed otherwise it was the LTV.
> 
> I wished they'd made the screen better with the ability to see flow graphs such as airway pressures etc. (can't always hear them in the aircraft).


I can see that being nice. I had VERY limited exposure to it, so I have little anecdotal experience to compare it with. And I use what tigger uses, so whatever limitations the Revel may have, it is still vastly superior to what I have available now.


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## RRTMedic (Nov 15, 2016)

G


VentMonkey said:


> Excellent podcast @medichopeful, Doc Weingart never disappoints. Kind of back to my original post, and something I think worth reiterating is that DKA is a _*form*_ of metabolic acidosis. I think in the prehospital setting oftentimes we are so caught up in DKA=Kussmaul breathing; in all actuality it is caused by *any form* of metabolic acidosis, and at this stage in the game these patients are very sick. I think this is worth bringing up because if you do come across a severe sepsis, or toxic OD with a metabolic compensatory component that may need intubation, they will need to be treated the same as though it was a severe DKA with impending respiratory failure. He mentions it in the podcast in reference to severe ASA toxicity, but here's a quick Merck manual link about it:
> 
> https://www.merckmanuals.com/profes...e-regulation-and-disorders/metabolic-acidosis
> 
> ...



Great point about thinking carefully about initiating spontaneous modes, etc. Again, I am always suffering from 'identity loss' and frequently forget that the ICU is a different place than in the back of an ambulance or aircraft. 

Generally, these patient's don't have a ventilatory problem (the respiratory system is wack trying to compensate). Paralyzing is noble, but of course sedation is preferred. Really, you will never fix a metabolic problem with your ventilator, but it is definitely something you want to maintain (low CO2 is what I mean). Often, I've seen these patients move from nasal cannula, to bipap, to ventilator as providers try to fix their metabolic issue with a pulmonary intervention--almost never happens. 

I would caution using assist/control modes with these patients as high respiratory rates with demand volumes/pressures may result in air trapping, vent dyssynchrony, etc. This is one of the few times as an RT I would suggest SIMV (or if you're brave a spontaneous mode, provided their current pulmonary status is maintaining).


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## RRTMedic (Nov 15, 2016)

VentMonkey said:


> I liked that it had PRVC, but was a tad disappointed otherwise it was the LTV.
> 
> I wished they'd made the screen better with the ability to see flow graphs such as airway pressures etc. (can't always hear them in the aircraft).



Ah, PRVC... the 'mindless' mode. You know, in the respiratory profession, it seems that many RTs revert to PRVC because of its automative functions. BUT, it's rare to find personnel who really understand PRVC and what it is doing for the patient.

Here's a challenge: You have a patient who is not tolerating PRVC and obviously needs more flow. You try to decrease the inspiratory time, as you would in Volume or Pressure Control (decrease inspiratory time means increased flow rate in these modes). However, nothing changes. So how do you increase your flow rate in PRVC?


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## TXmed (Nov 15, 2016)

we have the impact AEV where i work. 

on these patients are difficult. i have found that with our vent A/C pressure actually makes them more comfortable (i suspect it is because of there tired respiratory muscles) so i will put them on something along the lines of PIP-20 PEEP-5-7 RR - 24-28 and adjust rise time accordingly. i like to use several small doses of ketamine or low dose propofol. then as they regain their drive i will lower the lower the trigger and PIP down to 10 as our vent will let them pull as much volume as they would like and the RR - 20-18 and they seem to self regulate pretty well if they continue to get better i will switch to NIV but ive rarely done that. and titrate sedation lower to only treating for anxiety, i also talk to the patient very regularly. 

the main trick is getting them from the hospital vent to ours. that is where i will give ketamine or up the propofol for 1-2 minutes (nothing crazy) to help them go from one breathing system to another a little more comfortable. 

im a big believer on making your patient comfortably without just sedation. so i will sit them up, tinker with the vent (such as rise time, trigger level, I:E ratio) talk to them, maybe reduce my vent tubing by cutting it, headset, and talk to them the whole time.

@RRTMedic i use A/C mode on these patients as the SIMV mode will lead me down nothing but alarms every time the patient follows a decent breath with a short rapid breath as the SIMV will not assist them as much as they need to. i think this is vent specific. so ive learned to use A/C and have not encountered any breath stacking as of yet (but i am on the look out). this may be because the impact is pressure triggered instead of low triggered but i am not sure.


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## RRTMedic (Nov 15, 2016)

TXmed said:


> i use A/C mode on these patients as the SIMV mode will lead me down nothing but alarms every time the patient follows a decent breath with a short rapid breath as the SIMV will not assist them as much as they need to. i think this is vent specific. so ive learned to use A/C and have not encountered any breath stacking as of yet (but i am on the look out). this may be because the impact is pressure triggered instead of low triggered but i am not sure.



Don't get me wrong; I'm a big advocate for assist/control. I don't care what the FP-C exam says about "patient's spontaneously breathing should be placed in SIMV." Assist/control, when good settings are inputted, can do amazing things for patients. Decreased muscle fatigue, normalization of arterial gases, etc. I love love love A/C and will always use it until it isn't tolerated. 

And yes, you are very much correct, it does depend on your ventilator. A lot of vents don't give good pressures (ie. ran into a vent today that constantly had the actual PEEP way below the set PEEP). Most of my vent experience has been with a Servo i in the hospital; a great ventilator that provides accurate pressures and when in a spontaneous mode, gives GREAT pressure support. 

LTVs are a little disappointing when you need spot on pressures/volumes. Great for a transport environment, not so much for the ICU. 

And of course, the transport environment does provide more liberty with gracious amounts of sedation and paralytics... a big no no in the ICU where 'sedation vacation' is a norm. 

**sigh** I often forget my place and my audience... it has always been a challenge for me to separate the ICU and the ambulance. Great discussion though! It is encouraging to see my fellow paramedic colleagues care so much about vent management; a step in the right direction in giving the EMS/paramedic profession the place it deserves.


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## RRTMedic (Nov 15, 2016)

TXmed said:


> we have the impact AEV where i work.
> 
> on these patients are difficult. i have found that with our vent A/C pressure actually makes them more comfortable (i suspect it is because of there tired respiratory muscles) so i will put them on something along the lines of PIP-20 PEEP-5-7 RR - 24-28 and adjust rise time accordingly. i like to use several small doses of ketamine or low dose propofol. then as they regain their drive i will lower the lower the trigger and PIP down to 10 as our vent will let them pull as much volume as they would like and the RR - 20-18 and they seem to self regulate pretty well if they continue to get better i will switch to NIV but ive rarely done that. and titrate sedation lower to only treating for anxiety, i also talk to the patient very regularly.
> 
> ...



Another thing I forgot to mention is pressure support in SIMV... a good pressure support setting in SIMV goes a long way as well. Typically, I start at a pressure support of 10 cmH2O and titrate from there.... definitely helps with muscle fatigue and air hunger.


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## VentMonkey (Nov 15, 2016)

RRTMedic said:


> Ah, PRVC... the 'mindless' mode. You know, in the respiratory profession, it seems that many RTs revert to PRVC because of its automative functions. BUT, it's rare to find personnel who really understand PRVC and what it is doing for the patient.
> 
> Here's a challenge: You have a patient who is not tolerating PRVC and obviously needs more flow. You try to decrease the inspiratory time, as you would in Volume or Pressure Control (decrease inspiratory time means increased flow rate in these modes). However, nothing changes. So how do you increase your flow rate in PRVC?


http://www.uthscsa.edu/academics/health-professions/departments/emergency-health-sciences

Decelerating flow patterns is my non-RT guess.



RRTMedic said:


> Another thing I forgot to mention is pressure support in SIMV... a good pressure support setting in SIMV goes a long way as well. Typically, I start at a pressure support of 10 cmH2O and titrate from there.... definitely helps with muscle fatigue and air hunger.


SIMV with a PS of 10 is my go to as well, unless the patient is completely paralyzed then I would default to A/C, but again depending on who you talk to you could argue for either in the prehospital environment as most transport times (excluding LDT's) wouldn't make a huge difference.

I digress however, as I enjoy prehospital vent management and think it takes quite a bit of critical thinking skills.


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## TXmed (Nov 15, 2016)

@RRTMedic I never thought the PEEP could be off like that. something to think about next time i got the vent out.

@VentMonkey i agree with that


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## RRTMedic (Nov 15, 2016)

VentMonkey said:


> Decelerating flow patterns is my non-RT guess.



So it took me a long time to figure this out, but I eventually got to wrap my head around this. 

And yes, decelerating flow is one of the mechanisms that PRVC used to prevent increased peak airway pressure.

But, to increase flow in PRVC, you gotta know the concepts surrounding PRVC. PRVC works based upon patient effort and added vent support. In essence, the ventilator (breath by breath) determines how hard the patient works during a respiratory cycle and then compensates for any slack in the patients spontaneous efforts. This is another mechanism that PRVC uses to decrease peak airway pressures and plateau pressures. 

So, if you have a tidal volume set at 350 ml and the patient (for the sake of explanation--its more complicated in reality) makes enough effort to breath at 350 ml, the vent provides little support because the patient is doing much of the work. That means that the flow is DECREASED because the patient is doing all the work. But, in reality, this patient is struggling to take that 350 ml breath and is becoming tired and air hungry... the solution? Increase the flow. How do we do that (in prvc?).... increase the tidal volume. More tidal volume will result in greater flow because the vent will have to add more support if the patient only feels like generating a 350 ml breath. 

Hope that makes sense... I'm a visual learner so trying to explain it in words can be a challenge.


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## VentMonkey (Nov 15, 2016)

TXmed said:


> we have the impact AEV where i work.
> 
> on these patients are difficult. i have found that with our vent A/C pressure actually makes them more comfortable (i suspect it is because of there tired respiratory muscles) so i will put them on something along the lines of PIP-20 PEEP-5-7 RR - 24-28 and adjust rise time accordingly. i like to use several small doses of ketamine or low dose propofol. then as they regain their drive i will lower the lower the trigger and PIP down to 10 as our vent will let them pull as much volume as they would like and the RR - 20-18 and they seem to self regulate pretty well if they continue to get better i will switch to NIV but ive rarely done that. and titrate sedation lower to only treating for anxiety, i also talk to the patient very regularly.
> 
> ...


Interesting stuff, great posts guys. @TXmed I can only say that the Eagle (impact) was also trialed, and personally I wasn't a fan of this one either. It seemed lacking, and somewhat archaic, IMO, but this is just me.

I would have to say for me the Hamilton T1 is tops for prehospital ventilators, and the ReVel a close second. @RRTMedic excellent point made about PRVC being a "press and let it do it's thing mode", I can totally see this, though admittedly, the Hamilton offering the next step up, or it's version of something similar in ASV could be easily construed in the same manner I suppose.


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## RRTMedic (Nov 15, 2016)

@VentMonkey A good overview of PRVC http://www.respiratoryupdate.com/members/PRVC_Pressure_Regulated_Volume_Control.cfm

PRVC is aka as variable pressure control, volume control plus... and whatever a manufacturer feels like naming on their vent! haha


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## VentMonkey (Nov 15, 2016)

RRTMedic said:


> So it took me a long time to figure this out, but I eventually got to wrap my head around this.
> 
> And yes, decelerating flow is one of the mechanisms that PRVC used to prevent increased peak airway pressure.
> 
> ...


It does, and I recently went over this, though I can't recall if it was in my lecture notes from my class, or it was one of Eric's podcasts on FlightBridgeEd. I am going to say it's the latter, but thank you for sharing it with all of us, and re-explaining it to me as well(hey, I'm a "whatever-I-can-get-my-hands-ears-and-eyes-on" kind of learner).


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## VentMonkey (Nov 15, 2016)

RRTMedic said:


> @VentMonkey A good overview of PRVC http://www.respiratoryupdate.com/members/PRVC_Pressure_Regulated_Volume_Control.cfm
> 
> PRVC is aka as variable pressure control, volume control plus... and whatever a manufacturer feels like naming on their vent! haha


Thanks, yeah, the name is pretty self-indicative, but I agree wrapping your head around some of the concepts of ventilator, and respiratory management can be a fun challenge, so whomever it was who questioned what it was an RT "does" in the prehospital environment, let alone their place in it, well here's living proof. This is stuff that most paramedics (definitely including myself) could stand to benefit from.


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## RRTMedic (Nov 16, 2016)

VentMonkey said:


> Thanks, yeah, the name is pretty self-indicative, but I agree wrapping your head around some of the concepts of ventilator, and respiratory management can be a fun challenge, so whomever it was who questioned what it was an RT "does" in the prehospital environment, let alone their place in it, well here's living proof. This is stuff that most paramedics (definitely including myself) could stand to benefit from.



Thank you so much! That means a lot to me... As I've said before to you, I'm a paramedic first and a Respiratory Therapist second. There are times when the knowledge does benefit you in a 911 system. Just curious, anyone know of flight companies in your area that run RN/RT or Medic/RT? Provided it isn't a pediatric transport service...


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## EpiEMS (Nov 16, 2016)

RRTMedic said:


> Thank you so much! That means a lot to me... As I've said before to you, I'm a paramedic first and a Respiratory Therapist second. There are times when the knowledge does benefit you in a 911 system. Just curious, anyone know of flight companies in your area that run RN/RT or Medic/RT? Provided it isn't a pediatric transport service...



Not strictly my "area", but I believe DHART does. They're highly regarded, I'm told. (I had the pleasure of taking my EMT course with a DHART-hopeful RT.)


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## Carlos Danger (Nov 16, 2016)

RRTMedic said:


> Just curious, anyone know of flight companies in your area that run RN/RT or Medic/RT? Provided it isn't a pediatric transport service...



MedCenter Air in Charlotte, NC


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## VentMonkey (Nov 16, 2016)

Chase said:


> We have the Revel on the helicopter.





VentMonkey said:


> I'm keeping my fingers crossed we get the Hamilton as our next vent.


Just an update: looks like it's official, our service will be switching to the Hamilton T1. I'm pretty stoked myself.


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## StCEMT (Nov 16, 2016)

VentMonkey said:


> Just an update: looks like it's official, our service will be switching to the Hamilton T1. I'm pretty stoked myself.


That's a nice lookin vent, wanna trade?


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## RRTMedic (Nov 16, 2016)

Remi said:


> MedCenter Air in Charlotte, NC



Glad you mentioned those guys... unfortunately, that is the only service I know of... honestly wish it were more common. Provided, of course, the RT has a medic background... which most of the flight therapists do.


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## Carlos Danger (Nov 17, 2016)

RRTMedic said:


> Glad you mentioned those guys... unfortunately, that is the only service I know of... honestly wish it were more common. Provided, of course, the RT has a medic background... which most of the flight therapists do.



There are a few other HEMS programs that fly with RRT's, but I think MCA is the only one where they practice to the full scope of their training and follow the same protocols as the flight nurses. And of course there are many programs that utilize RRT's in specialty transports.

I don't think it's true that _most_ of the RRT's at MCA have an EMS background, but some do. I worked at their base in SC, and everyone who flew there had to be a paramedic. The RRT's at that base voluntarily went through the entire paramedic program (not a bridge program) while working full time, and a couple voluntarily did far more than the minimum hours on the ambulance just because they wanted the experience. Three of the four flight nurses at that base had been paramedics before getting into nursing. It definitely showed, I think, at times. We had a really good crew at that base.


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## MSDeltaFlt (Nov 24, 2016)

ParamedicStudent said:


> I have a couple questions about EtCO2:
> 
> Let's talk about patients with COPD/Asthma. I know they retain CO2 due to physical damage to tissues, so that does that mean that their end tidal CO2 would be low on the monitor, because they're holding back CO2 and not all of it is being released out when they exhale? How about when they're having an exacerbation? Is it the same logic?
> 
> ...


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