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Tidal Volume related to AHIs?
#1
Question 
Recent discussion about tidal volume made me curious about that line in Sleepyhead which I'd never looked at.  I was looking over the last several nights, and noticed that I tend to take a deeper breath (that's what tidal volume is, right?) immediately after an "event". 

Does that just mean that my body is responding how it should, in order to make the event stop? 

I tried to see if there was a pressure association; like perhaps the pressure raised which would trigger my breath, but it doesn't seem like it.

Thoughts? 

(I'm just trying to better understand the data, the machine, and my sleep apnea.)

Here's the screenshot:
[Image: PdcpnEil.png]
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#2
from Wikipedia
"Tidal volume is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied. In a healthy, young human adult, tidal volume is approximately 500 mL per inspiration or 7 mL/kg of body mass."
                                                                                                                                                                                  
Please organize your SleeyHead screenshots like this.
I'm an epidemiologist, not a medical provider. 
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#3
Hold your breath for 30 seconds.  Now breath again.  What is the first thing you do?  Take a large breath?  The term for these is Recovery Breath.  Your body has become oxygen deprived and the brain wants more NOW!  It is not making the event stop, it is recovering from the effect of the event.  I would expect longer events to correlate to larger or multiple recovery breaths.
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#4
(03-11-2017, 11:42 PM)chill Wrote: Hold your breath for 30 seconds.  Now breath again.  What is the first thing you do?  Take a large breath?  The term for these is Recovery Breath.  Your body has become oxygen deprived and the brain wants more NOW!  It is not making the event stop, it is recovering from the effect of the event.  I would expect longer events to correlate to larger or multiple recovery breaths.

Ok, I held it for 10. That's a long time. But ok, yeah, I did take a deeper breath to recover. Ah, ok, so it's a recovery breath. I see. Recovering from the event. I see. 

So, what is causing the event to end?  If nothing is causing it to end, I have to wonder what the point of xpap is. Then again, I know that xpap has decreased my AHI (so that would mean it has decreased the *number* of events?) and has increased my quality of life. But does xpap not affect events when they occur?  Or is it preventing the event from being a worse event (ie: keep it at a flow limit rather than a full on OA)?
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#5
CPAP and APAP machines can't do much while an apnea is actually in progress. They look out for precursors such as flow limitation and snoring and increase pressure to head off an apnea. And of course the base pressure should be sufficient to stop a lot of events and precursors before they get started. Resmed machines take a more aggressive approach to this, which is the reason some users find the Dreamstation more comfortable. The Dreamstation also does a bit of experimenting with pressure (which you can see as little spikes in the graph) where it bumps the pressure up periodically to see if it improves your breathing.

ASV machines on the other hand adjust pressure on a breath-by-breath basis, even while an apnea is occurring. They are really really good, but they also cost a fortune.
DeepBreathing
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#6
Oooh, ok. That's very interesting.

What do you mean by "to see if it improves your breathing"? What would improvement look like? More consistent rhythm? Not shallow breathing? Or just decreasing the precursors of apneas?
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#7
(03-11-2017, 11:39 PM)Beej Wrote: from Wikipedia
"Tidal volume is the lung volume representing the normal volume of air displaced between normal inhalation and exhalation when extra effort is not applied. In a healthy, young human adult, tidal volume is approximately 500 mL per inspiration or 7 mL/kg of body mass."

So what  should it be for an old fart like me? Wink
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#8
An old image repeat, but there are several of us on the forum that have tidal volumes and minute vents that may be above average. Mine ranges from the low 600s to mid 700s and varies quite a bit. If you feel your ventilation is below average, get a bilevel machine and use some pressure support. Volume will increase. As far as what is normal for you, just calculate it based on the formula of 7 mL * ideal weight in Kg and that is a rough approximation of tidal volume at rest. It would not be unusual for your Tv during sleep to be lower.

Don't take the machine stats too seriously. If you want to know your respiratory health, ask your doctor to do a forced exhaled volume (FEV) and/or forced vital capacity (FVC) tests. http://www.webmd.com/lung/tc/forced-expi...c-overview
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#9
(03-12-2017, 04:11 AM)Hydrangea Wrote: What do you mean by "to see if it improves your breathing"?  What would improvement look like?  More consistent rhythm?  Not shallow breathing?  Or just decreasing the precursors of apneas?

Decreasing the precursors.  The pressure of anything other than ASV is not enough to meaningfully affect the inflation of your lungs.
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#10
(03-12-2017, 01:41 PM)chill Wrote:
(03-12-2017, 04:11 AM)Hydrangea Wrote: What do you mean by "to see if it improves your breathing"?  What would improvement look like?  More consistent rhythm?  Not shallow breathing?  Or just decreasing the precursors of apneas?

Decreasing the precursors.  The pressure of anything other than ASV is not enough to meaningfully affect the inflation of your lungs.

Any device capable of delivering pressure support can support higher ventilation volumes and gas exchange.
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