Vent Questions

Aprz

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I am using IA Med to study for FP-C. They had two test questions I got wrong. One, I have an idea why I got wrong, but the other one I don't. I sent a message to the instructor/support, but haven't heard back yet. I was hoping I could get help?

The first question was the patient has COPD exacerbation.

Vent settings are

AC
Vt 550
F 20
Inspiratory time 1 sec
I:E 1:2
FiO2 1.0
PEEP 5
Pplat 26

It gave an ABG.

pH 7.18
PCO2 72
HCO3 27
PaO2 70

It asked which vent setting should I change.

a) increase expiratory time
b) increase inspiratory time
c) increase Vt
d) increase PEEP

So when I took the test, I believed the ABG showed a partially compensated respiratory acidosis and the PaO2 is low. I felt like increasing the respiratory rate, even though it is already 20, would've solved both acidosis and hypoxia. This was not the correct answer. Reflecting back, that's already a high minute volume so my next best guess is increase expiratory time. I felt the I:E ratio should be 1:4, not 1:2, with COPD or asthma. I feel like this would help blow off CO2 and help with acidosis, but didn't feel like this would fix the hypoxia. Maybe it is normal for someone with COPD? I don't know. Anyways, that was my next best guess, but it doesn't give you the correct answer or explanation so that is why I am asking you guys.

The next question I have literally 0 idea what is wrong. It just gives vent settings only with no clinical vignette.

AC
F 18
Vt 450
inspiratory time 0.8 sec
FiO2 1.0
PEEP 5

Pplat 20
PIP 22

It asked what would you change.

a) increase Vt
b) increase FiO2
c) decrease F
d) increase expiratory time
e) none of the above

I chose e, none of the above, which was wrong.

I know that it cannot be b either since FiO2 is 1.0 and cannot go higher. I feel like the settings look sane, but I don't know much about PIP and Pplat. If I had to do process elimination, I know PIP and Plat would be effected by Vt so that would be my next guess, but that is trying to beat the test rather than just learn. I want to understand what I am not seeing or what is wrong here. To me, I just thought PIP <35 and Pplat <30 are good enough, that is what IA Med taught or what I thought they taught anyways, but I guess there is more. I also learned about Pplat / AC with air stacking so wonder if that is another issue?

I already passed the IA Med tests, but if I go on to be a flight medic, I want to do my patients justice and know these things... not just beat a test.

Thank you!
 
Last edited:

VentMonkey

Family Guy
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I believe you’re on to something (hint, hint) with increasing the I:E ration.

I agree with the partial comp. respiratory acidosis. PaO2 seems fine (remember <60 is cause for concern).

They teach the combined PaO2 (<60) / PaCO2 (>) 55 (I’ve also heard 50)/ pH (<) 7.20= Resp. Failure (hypoxemia) parameters.

I’ve had a couple of questions I’d submitted as well and had yet to hear back from them. It seems like one of their few drawbacks. And they don’t explain the rationale behind the answers either, which I sort of wish they would.

Either way, I applaud your efforts at both reaching out, and not wanting to learn just enough to pass an exam. I’m sure some ICU-level folks will chime in and offer up their input as well.

You could also go back and redo the test until you got the answer correct, then reasearch the reasoning in your resources and videos. GL on your exam.
 

E tank

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I am using IA Med to study for FP-C. They had two test questions I got wrong. One, I have an idea why I got wrong, but the other one I don't. I sent a message to the instructor/support, but haven't heard back yet. I was hoping I could get help?

The first question was the patient has COPD exacerbation.

Vent settings are

AC
Vt 550
F 20
Inspiratory time 1 sec
I:E 1:2
FiO2 1.0
PEEP 5
Pplat 26

It gave an ABG.

pH 7.18
PCO2 72
HCO3 27
PaO2 70

It asked which vent setting should I change.

a) increase expiratory time
b) increase inspiratory time
c) increase Vt
d) increase PEEP

So when I took the test, I believed the ABG showed a partially compensated respiratory acidosis and the PaO2 is low. I felt like increasing the respiratory rate, even though it is already 20, would've solved both acidosis and hypoxia. This was not the correct answer. Reflecting back, that's already a high minute volume so my next best guess is increase expiratory time. I felt the I:E ratio should be 1:4, not 1:2, with COPD or asthma. I feel like this would help blow off CO2 and help with acidosis, but didn't feel like this would fix the hypoxia. Maybe it is normal for someone with COPD? I don't know. Anyways, that was my next best guess, but it doesn't give you the correct answer or explanation so that is why I am asking you guys.

The next question I have literally 0 idea what is wrong. It just gives vent settings only with no clinical vignette.

AC
F 18
Vt 450
inspiratory time 0.8 sec
FiO2 1.0
PEEP 5

Pplat 20
PIP 22

It asked what would you change.

a) increase Vt
b) increase FiO2
c) decrease F
d) increase expiratory time
e) none of the above

I chose e, none of the above, which was wrong.

I know that it cannot be b either since FiO2 is 1.0 and cannot go higher. I feel like the settings look sane, but I don't know much about PIP and Pplat. If I had to do process elimination, I know PIP and Plat would be effected by Vt so that would be my next guess, but that is trying to beat the test rather than just learn. I want to understand what I am not seeing or what is wrong here. To me, I just thought PIP <35 and Pplat <30 are good enough, that is what IA Med taught or what I thought they taught anyways, but I guess there is more. I also learned about Pplat / AC with air stacking so wonder if that is another issue?

I already passed the IA Med tests, but if I go on to be a flight medic, I want to do my patients justice and know these things... not just beat a test.

Thank you!
They're looking to make you make the expiratory time longer, the goal being exhaling more CO2, so like @VentMonkey said, you're right. In the real world, you'd prolly have to change more than that to drive the CO2 down, but that's another conversation.

That second one is an odd question...not being able to read minds, I'd say that with a rate that fast, a slower i time would give a lower PIP.
Nothing wrong with 22 but, there it is...the usual i:e is 1:2 so, playing along, if there was only one thing I'd change, I guess it'd be that. Not like .2 seconds is a big deal at all tho....

But...you can't raise fiO2 so that rules B out....there's no information that makes you want to change tidal volume so I'd rule A out...same rationale for C...E is wrong...so....D
 

E tank

Caution: Paralyzing Agent
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...or you could say that if you're achieving that tidal volume with those acceptable pressures, why are you ventilating so fast? So I guess you could say drop the rate too...screwy question....
 
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A

Aprz

Forum Deputy Chief
Premium Member
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I asked another friend who is CCT-P and she didn't know the answer to the second question. She thought it looked sane too. I have a FP-C friend I am going to ask, but not tonight.
 

Peak

ED/Prehospital Registered Nurse
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I’ll throw a couple thoughts at it, but to be transparent for anyone reading this I never had FP-C. I do have a myriad of other critical care certs relevantly including CEN and CCRN.

When I think of CO2 I mostly consider their bias flow/sweep/minute volume. If their other parameters are appropriate then this is really the driving force.

In the case of COPD we certainly want to avoid breath stacking and hyperinflation, but otherwise settings will be similar.

This patient does have a uncompensated respiratory acidosis with a low oxygen tension, granted with maximized Fio2.

Without knowing the patients ideal body weight it is difficult to know if the tidal volume is appropriate. That being said 550 mL is certainly generous for most adults so I doubt this needs to be changed.

If the patient is compliant to the vent I don’t thing increasing inspiration or excitatory time to be all that helpful. Increasing either is going to increase the risk of breath stacking and the relatively small amount of time that air is over the alveoli is probably not with it. That being said I would consider increasing inspiratory time first.

If I suspect that the patient has any significant amount of atelectasis then I would increase the peep. 5 is pretty low especially given the patients low pao2. Of any of the options I would increase peep first.

For the second question it’s difficult to tell what they are getting at, without a goal how are you supposed to adjust therapy?

A: without knowing IBW I can’t determine if Vt is appropriate.
B: like you said, you can’t increase fio2 above 1.
C: I guess 18 is on the high side for an adult, but it certainly isn’t inappropriate.
D: how do you increase expiratory time when you aren’t given it to start with?
 

Carlos Danger

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Poorly presented scenarios, but my presumption for question one is they want you to prolong the E time.

Question 2 is complete nonsense. Way too little info to make any decision whatsoever. I probably would also have chosen E based on the lack of info, but if that is "incorrect", my WAG would be to increase I-time. That is based solely on the inspiratory pressure.
 

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