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Should I try it or leave it be?
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vsheline Offline

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Machine: S9 VPAP Adapt (USA Model# 36007, not better 36037 or 36067)
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Post: #11
RE: Should I try it or leave it be?
(05-24-2014 03:11 PM)justMongo Wrote:  You say you breath shallow. Most people do during sleep. The Tidal Volume is a measure of how shallow.
There's a range of what normal TV is. Around 500 ml is normal.

The Philips Respironics has a CPAP machine (AVAPS ventilator) which can be adjusted to maintain a target tidal volume (Vt).

It suggests a target value of 8mL/kg of IDEAL (not actual) body weight.

Our "Ideal Weight" is based only on our height. So, according to the table below suggested by Respironics, 500 mL would be suggested target Vt value for someone who is 65 inches tall (5 foot 5 inches).

Height Ideal weight Vt (at 8ml/kg)
59" 52.0 kg 420 mL
61" 55.5 kg 440 mL
63" 59.0 kg 470 mL
65" 62.5 kg 500 mL
67" 66.5 kg 530 mL
69" 70.5 kg 560 mL
71" 74.5 kg 600 mL
73" 78.5 kg 630 mL
75" 83.0 kg 660 mL

(Personally, I think I do fine at about 85% of the value for my height in the table above.)

Take care,
--- Vaughn

Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
(This post was last modified: 05-25-2014 04:14 AM by vsheline.)
05-25-2014 04:08 AM
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Post: #12
RE: Should I try it or leave it be?
(05-24-2014 03:11 PM)justMongo Wrote:  Ever heard the saying, "If it ain't broke, don't fix it." Your numbers fall into that category.
I agree with justMongo here: If it ain't broke, don't fix it.

So rather than focusing on your excellent therapy numbers, you need to be asking yourself: How do you feel when you wake up? And how do you feel throughout the day?

If you are NOT yet feeling as well as you hoped, it's time to consider other potential causes.


(05-24-2014 03:23 PM)Marnid2014 Wrote:  
(05-24-2014 03:11 PM)justMongo Wrote:  You say you breath shallow. Most people do during sleep. The Tidal Volume is a measure of how shallow.
There's a range of what normal TV is. Around 500 ml is normal.


These are the stats from last night, the tidal volume is low, is this ok?

...

Statistics
Channel Min Med 95% Max
Tidal VolumeTidal Volume (ml)
W-Avg: 284.44 60.00 260.00 480.00 820.00

Tidal volume depends on the person (size is important!) and whether you're talking about WAKE breathing or SLEEP breathing.

Normal WAKE, but resting TV for a typical adult is approximately 500 mL per inspiration or 7 mL/kg of body mass. So that 500 mL "average TV" is based on an average weight of 71.43 Kg = 157.48 pounds. But there is quite a bit of variance on the numbers considered "normal" in the population.

In normal SLEEP breathing, the TV does go down, sometimes substantially. According to this research paper in Thorax the TV in REM sleep is often only 73-80% of what the resting wake TV is. The sleep TV is also lower than the wake TV in all other stages of sleep as well, often is 10-20% lower than the WAKE, but resting TV. And in most normal people, the SLEEP breathing is substantially shallower than their normal WAKE breathing.

If you weigh substantially less than 150 pounds, your tidal volume numbers are going to be far less: Take my own situation: I'm 5'1" tall and weigh about 105-110 pounds. And 110 pounds = 49.90 kg. So my WAKE, but resting average TV should be around 49.9 * 7 = 349.3 mL (call it 350 mL). My weighted average and median sleep TV (as measured by SH's computations) are both usually in the 280-300 mL range, which is 80%-86% of my expected WAKE, but resting TV.

In light of all this: Your median and weighted average TV may indeed be a bit on the low side, particularly if you weigh a lot. But it could just be that these numbers are normal for you. And if you are feeling decent when you wake up and decent during the daytime, I would assume that your TV numbers are "normal for you".
05-27-2014 10:21 AM
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