End tidal CO2 questions

[VentMonkey]

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.

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.

 

[RRTMedic]

@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

 

[VentMonkey]

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.

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).

 

[VentMonkey]

@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.

 

[RRTMedic]

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...

 

[EpiEMS]

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.)

 

[Carlos Danger]

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

 

[VentMonkey]

We have the Revel on the helicopter.

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.

 

[StCEMT]

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?

 

[RRTMedic]

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.

 

[Carlos Danger]

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.

 

[MSDeltaFlt]

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?

I've been gone for a while and I just saw this so please excuse me for the late response. I am not bashing in any sense of the word, but this is very important.

COPD does not guarantee CO2 retention. COPD does not guarantee a hypoxic drive. You only allow hypercapnia and hypoxia if you have supporting data stating that is their normal. Otherwise you have to treat the hypercapnia and hypoxia and get them to standard normal ranges. Please dear God do not treat capnography on COPD patients like the overused myth of "2L/min NC". Because doing that will do them a great disservice and increase their hospital stay.

As far as DKA goes, Diabetic Ketoacidosis, the operative word is "acidosis". Their body is trying to blow off CO2 to bring their pH up, but it's not working. The same reason why some of them might also be vomiting. To get rid of as much acid as possible. But, again, that is not working. With capno, you can monitor your pt's respiratory status and infer their acid base balance according to their clinical presentation.

In other words, treat your patient and not the machine.

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?