Setting Target Va on iVAPS machine

[zzzZorro]

Per suggestion, ‘Learned’ mode was run and provided: Target Pt. Rate- 17; Target Va- 6.9
 
The iVAPS Titration Protocol states: Set Target Va such that Vt is equal to 6ml/kg IBW. 
When Vt is set for 6ml/kg IBW the Target Va adjusts to 3.2 L/min, and Mv to 4.4L/min, and Vt/kg to 448 ml/kg IBW.  This is 26 ml/kg low for the Vt/kg setting for actual IBW.   My IBW off the Titration Study was “22.3 kg/m (square)”.  Weight would be 79kg [6 (ml/kg) x 79 = 474 (Vt/kg= 474 ml/kg IBW)  If the machine is set for Vt= 478 it reflects Target Va of 3.5 ml/min. (0.3 higher than when the suggested 6ml/kg is set)
 
DME confirmed setting Target Va for 5.2 “per Doctors prescription”.  So now I have 5.2; -and a ‘Learned’ 6.9; -the titration manual recommendation 3.2; -and a 3.5 derived from a IBW calculation.
 
Question would be, “anyone have an idea what it should be set to?”

[Sleeprider]

Hold my beer, and I'll try to calculate.  

This is a bit out of my league, but I think it's great you are grabbing on to this problem and understanding it and trying to optimize.  This does however sound like a question I would shoot into the doctor's office.  I have an app for that.  

[ajack]

Please make them titrate you and don't use a chart. Or the learn mode would be the accurate setting for me. even given the slight reduction of minute vent when asleep. I finished up getting my settings from sleepyhead.

who told you that was the target? I would guess that is of a healthy 20 year old kid.
I remember sleeprider for example has 10 minute vent from his charts he posted and I asked him about it at the time. I have just under 8 minute vent
If you gave sleeprider the 8 minute vent, he would have a hard night.

[zzzZorro]

Hold my beer, and I'll try to calculate.  
 This does however sound like a question I would shoot into the doctor's office.  I have an app for that.  

Seriously;  It took 13 days from December 22 to get a call from a nurses assistant telling me the Doctor has ordered a download from my machine and will have the DME contact me.  That only happened after bitching on the Patient Portal.  The call from the DME was two more days and Doctor ordered back up rate raised from 10-12.  The machine 'learned' 17 BPM and iVAPS titration guide says 'use actual BPM'...  DME told me the Doctors tell them the outcomes they desire and they do the settings. [GO FISH...]
I pretty well have taken Carte Blanche from lack of response and inaccuracies to sail my own ship
 

Please make them titrate you and don't use a chart. Or the learn mode would be the accurate setting for me. even given the slight reduction of minute vent when asleep. I finished up getting my settings from sleepyhead.

who told you that was the target? I would guess that is of a healthy 20 year old kid.
I remember sleeprider for example has 10 minute vent from his charts he posted and I asked him about it at the time. I have just under 8 minute vent
If you gave sleeprider the 8 minute vent, he would have a hard night.

Keep feeling like a Dumb-Arse here!  When you say "10 minute vent" and "8 minute vent" I read and re-read that was posted and have no idea what it means..
Sorry!

[ajack]

I would want the doctor to tell me why the learned mode was so different to what setting he wants. If he is basing it off your actual sleep study or off of a chart.
As you know, there are a lot of variables, both mechanical and the ability to exchange o2 and co2. so 2 people exactly the same size can have different minute ventilation, if their ability to exchange o2/co2 is degraded.
I was using myself and sleeprider as examples of how different people need different volumes of air per minute.


on sleepyhead, you have the median minute ventilation, that is the amount of air you breathe a minute
"Respiratory minute volume (or minute ventilation or minute volume) is the volume of gas inhaled (inhaled minute volume) or exhaled (exhaled minute volume) from a person's lungs per minute. It is an important parameter in respiratory medicine due to its relationship with blood carbon dioxide levels."

http://www.anaesthesia.med.usyd.edu.au/r...ation.html

Definitions

Ventilation is the process by which Oxygen and CO2 are transported to and from the lungs.

Tidal Volume (Vt) is the amount of gas expired per breath - typically 500ml at rest.

Deadspace Volume (VD) is the sum of the Anatomic Deadspace, due to the volume of the airways (typically 150ml), and Physiologic Deadspace, due to alveoli which are ventilated but not perfused (usually insignificant).

Minute Volume (VE) is the amount of gas expired per minute.

Alveolar Ventilation (VA) is the amount of gas which reaches functional respiratory units (ie, alveoli) per minute. VA = (Tidal Volume - Deadspace) x Respiratory rate

[ajack]

The machine will do the maths for you.
Dial in the "DME confirmed setting Target Va for 5.2" and see if the minute ventilation MV on the screen is close to the median minute vent from sleepyhead when not using backup. It will also give you the Vt and Vt/kg. As you change the Va by the dial, these numbers will also change. You can just read them off.


Whatever the Va is. It should be close, if you put in your height, have the pt at 17 (your median respiration rate) and is around the same as the median minute ventilation from your charts when not using backup.

The minute ventilation is an important numbers to me in the end. how you get there is in the settings. Just check and see if the new settings from the doctor are close to what sleepyhead was showing.

[zzzZorro]

Thanks ajack.

I get it now it is under the label 'MINUTE VENT' and the figure is 10 or in the tenths or 8 and the figure is in the tenths.

Could not cypher "10 Minute Vent"  from anything all of us posted

[zzzZorro]

Whatever the Va is. It should be close, if you put in your height, have the pt at 17 (your median respiration rate) and is around the same as the median minute ventilation from your charts when not using backup.

That averages about 7.2, just a touch over the 'Learned' 6.9 figure.

Thanks much appreciated

[ajack]

Now it is my turn to be confused, in your first post you said your Va was 6.9?
Is 7 your minute vent Med column number off of sleepyhead, averaged over a few nights?
(This is as I understand it. learn mode is using the machine for 20 minutes while awake or dozing off, while laying down and resting. The last 10 minute of data used. It measures your breathing and gives you numbers to accept or reject. With my breathing, I have a higher minute vent and tidal volume when awake, so it skews my data. I used the nightly average off of S mode. I think it's more accurate for me. You may find the learning mode is more accurate for you. we are all guessing here, nothing can replace a sleep titration study.)

when you dial in the doctors Va 5.2, what does the screen say for MV L/min numbers?

In sleepyhead, without a backup rate mode charts. If the Minute vent in the Med column number, is similar to the ST-A screen MV L/min. Using the Va 5.2. it should be close enough
Or saying it another way.
If the Va 5.2 that the doctor wants, Has the MV on the screen, around median minute vent of sleepyhead or resscan. I would think it's close enough, till you get a face to face with him.

If the sleepyhead chart, Minute vent, Med column number is a long way out, I would ask to stick to ST, till you see him face to face or sort it out with the DME. I wouldn't use any other Va number. If you don't use the doctors Va settings, he is going to be annoyed. He is the guy you need to keep on side.

[zzzZorro]

Welcome to the Club
 
Now it is my turn to be confused, in your first post you said your Va was 6.9?
 
Yes, from the ‘Learning’ mode you suggested previously- following ResMed instructions.

Is 7 your minute vent Med column number off of sleepyhead, averaged over a few nights?
 
Yes, went back over six or so charts and it is about 7.2  mostly from CPAP mode which has been giving me much better AHI.
 
When you dial in the doctors Va 5.2, what does the screen say for MV L/min numbers?
 
6.7 L/min and 561 ml

In sleepyhead, without a backup rate mode charts. If the Minute vent in the Med column number, is similar to the ST-A screen MV L/min. Using the Va 5.2. it should be close enough..

SleepyHead is 7.0+-  And, ResScan  in S mode was 7.0
 
The chart you posted shows me at 600ml.  So, from that the Doctors Va 5.2 at 561 ml would be in the ball park.
 
 
If the sleepyhead chart, Minute vent, Med column number is a long way out, I would ask to stick to ST, till you see him face to face or sort it out with the DME. I wouldn't use any other Va number. If you don't use the doctors Va settings, he is going to be annoyed. He is the guy you need to keep on side.
 
The machine was run in the ST mode one night and was the worst yet AHI-47.96 (remember there is no CA/OA differentiation)
CPAP mode has been consistently better than anything else. 
Interesting how the original sleep study ‘failed’ CPAP and the ‘journey to nowhere’ began..