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Air pressure hurting inside nose
#11
RE: Air pressure hurting inside nose
Thank you for your reply... Math has never been a strong point..so appreciate  your skills in figuring it out..

In a few days I'll hook it up here at home with the HME and see what happens...


Thanks
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#12
RE: Air pressure hurting inside nose
Do you know how I can turn down the pressure ?

I don't see a listing for a manual  on the board for the Transcend ezex - though I may be wrong..

Thank you  Thanks
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#13
RE: Air pressure hurting inside nose
It is there as a link to more information. This is that link:
http://www.apneaboard.com/forums/Thread-...PAP-System
PaulaO

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#14
RE: Air pressure hurting inside nose
Go to the “Private Files and Links Forum”
Scroll down until you find the thread for  “Somnetics software for Transcend Cpap System.”

I believe you can find the Clinicians manual there.
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#15
RE: Air pressure hurting inside nose
Thank you 

Im going do a few experiments with the unit this weekend... and if need be than Ill try (ver conservatively) reducing pressure..

Really appreciate you and this boards help

Shy
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#16
RE: Air pressure hurting inside nose
The shorter tubing is definitely the issue, and your machine will have no idea that it is happening.

Whenever you're dealing with air in an enclosed space, you have to take into account what is called static pressure drop.  Static pressure drop is the difference between the pressure at the beginning of the space, i.e. where your CPAP hooks up to your tube, and the end of the space, i.e. where the tube connects to your mask.

Larger diameter tubes have less static pressure loss, but require more air before you can build up pressure.  Smaller diameter tubes have greater static pressure loss, but require less air to build up pressure.  Your CPAP is programmed to expect the static pressure drop for a 6 foot hose of a standard diameter. That's why if you use slimine tube that some manufacturers provide, you have to tell the machine so that it can increase the pressure that it feeds into the tube so as to ensure that you get the same pressure at the end of the tube. The machine has no way of knowing that you're using a tube that isn't the standard tube unless you tell it.

When two tubes have the same diameter, the longer tube has a greater pressure loss.  And a shorter tube has a less pressure loss.  So, if you shortened your tube, you reduced the pressure drop and increased the pressure being delivered to your mask. Your CPAP has no way to know about this change, because you haven't told it, and it doesn't have any way to measure the actual pressure at the end of the tube. So, it will continue to assume that static pressure drop that is normaly with a 6 foot hose and will continue showing you the pressure that it thinks you're getting.

Tube constrictions, such as having a nasal pillow mask at the end of the hose, will also increase the static pressure drop.  That's why the CPAP has an adjustment for the mask type.  It will adjust the pressure it delivers in an attempt to account for the pressure drop at the mask.  Full face masks have the lowest pressure loss and will thus have a lower starting pressure than Nasal Pillows, which have the highest pressure loss.  Nasal masks are in the middle.
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#17
RE: Air pressure hurting inside nose
Thank you so much...

Thats kind of what I thought... I have small transcend ezex... not sure how I should tell it I have a shorter tube..

Suggestions ?
Thanks
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#18
RE: Air pressure hurting inside nose
Reznik, I think you have it backwards about the masks.
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#19
RE: Air pressure hurting inside nose
I don't think so... But, just to clarify:

1.  Full Mask -> lowest pressure drop between hose connection and your body.

2.  Nasal Mask -> More pressure drop between hose connection and your body.  CPAP will increase pressure coming out of the machine to compensate if you tell the CPAP you are using this kind of mask.

3.  Nasal Pillow Mask -> Even more pressure drop between hose connection and your body than #2.  CPAP will increase pressure coming out of the machine even more than #2 to compensate if you tell the CPAP you are using this kind of mask.

So, if 5 hypothetical units of pressure go into a hypothetical mask, a full mask might have a static pressure loss of 1 hypothetical unit and deliver 4 of those hypothetical units to your body, a nasal mask might have a static pressure loss of 2 hypothetical units and deliver 3 of those hypothetical units to your body, and a nasal pillow mask might have a static pressure loss of 3 hypothetical units and deliver 2 of those hypothetical units to your body.  Again, these are made up, hypothetical numbers to illustrate the point and don't reflect the actual pressures involved or the drops. 

So, if you tell your CPAP that you're using a face mask, it will would increase the pressure by (hopefully) 1 hypothetical unit over what it says it is delivering in order to compensate for the static pressure loss. If you tell it you're using a nasal mask, it will would increase the pressure by (hopefully) 2 hypothetical units over what it says it is delivering in order to compensate. And if you tell it you're using a nasal pillow mask in this hypothetical, it would increase the pressure by (hopefully) 3 hypothetical units over what it says it is delivering in order to compensate. With these adjustments, a machine showing 5 units would actually deliver to 5 units to your face, even though it is actually blowing a bit harder at the machine output.

There's also similar math involved in the tubes, which I covered above.

You can duplicate the concept using a straw.  Blow through one end of the straw and put your hand at the other end to feel the pressure.  Now, slowly squeeze the middle of the straw.  As you squeeze the straw, you'll have to blow a lot harder to get the same pressure at the other end.
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#20
RE: Air pressure hurting inside nose
My suggestion would be to use the longer tube.  Smile

Your machine expects it, and it is increasing the airflow to account for it.  By using a shorter tube, you're delivering more of that extra pressure that is supposed to dissipate in the 6-foot tube to your body.  You could try reducing the pressure settings on the machine, but without a pressure gauge, you won't be able to tell if you reduced it too much or not enough.

You could also ask a mechanical engineer. There are formulas for this sort of thing and an engineer who knows how to do the math could probably tell you the difference in static pressure loss between a 6-foot host and 4-foot hose.

I think that its an exponential situation, so its not as simple as figuring out the total loss for 6-feet, dividing by 6, and then multiplying by 4. But, I'm not an engineer and so I don't know for sure..

(10-10-2017, 04:01 PM)suzengrace Wrote: Thank you so much...

Thats kind of what I thought... I have small transcend ezex... not sure how I should tell it I have a shorter tube..

Suggestions ?
Thanks
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