Hose diameter question

[Osiris357]

I’m not surprised, my DME told me the heated hose was a waste of time because you can’t control your humidity and that it didn’t matter what setting your mask type is set to (pillows,full face and nasal)

Sometimes I wonder what there background is in this field before getting the job!

Back to the hose size. It definitely matters so you get the correct pressure from the blower. At this point I’d just buy the right hose so you aren’t waiting for these clowns to get there act together. I’ve done exactly that. It took them over a month to get me my new style mask and I knew it would take forever so I bought it online the day I told my doc about it. 

Good luck getting through to them

[Sleepster]

There will be slight differences in pressure at the mask end of tubing of different diameters and lengths. But since you have a machine that auto-adjusts the pressure none of that will make a difference as long as you keep your eye on your data.

[Osiris357]

Really? Everything I’ve read anywhere has said if your machine is calibrated for slimline absolutely do not use a 22mm hose. The industry has been known to be full of it as we all have figured out though.

[Matt00926]

A standard hose has an inner diameter of 19mm. It's the end caps that are universally 22mm. Slimline has an inner diameter of 15mm. Any standard hose is 19mm - they are all the same more or less. Even the climateair max from ResMed is still 19mm inner diameter. Totally normal. Never seen an inner diameter of 22mm in my life. Respironics labeling 22mm as a hose type seems to just be arbitrary and misleading.

[123456]

Thank you to everyone for your input.

[Osiris357]

Sorry that should’ve said 19mm not 22

[Sleepster]

Really? Everything I’ve read anywhere has said if your machine is calibrated for slimline absolutely do not use a 22mm hose.

You go into the menu to select the diameter of the hose you're using. Let's say the machine is set for slimline tubing, which is 15 mm in diameter. And let's say that you get a 0.5 cm drop in pressure along that tubing, so if you set a pressure of 11.0 cm the machine will actually produce 11.5 cm of pressure so that the pressure at the mask end of the tubing is 11.0 cm. If you left the menu setting at 15 mm and used a 22 mm diameter hose the pressure at the mask end of the tubing might be 11.2 cm because you lose only 0.3 cm of pressure with the wider tubing. To fix the problem you simply go into the menu ad change the tubing diameter to 22 cm.

But if you have a machine that auto-adjusts the pressure, it will deliver whatever pressure it figures you need

[Osiris357]

Makes sense sleepster since it compensates for leaks why wouldn’t it compensate for less back pressure from a larger diameter hose. Everything I read must have been old. Didn’t look to see when the articles were published and most importantly by whom

[Sleeprider]

You go into the menu to select the diameter of the hose you're using. Let's say the machine is set for slimline tubing, which is 15 mm in diameter. And let's say that you get a 0.5 cm drop in pressure along that tubing, so if you set a pressure of 11.0 cm the machine will actually produce 11.5 cm of pressure so that the pressure at the mask end of the tubing is 11.0 cm. If you left the menu setting at 15 mm and used a 22 mm diameter hose the pressure at the mask end of the tubing might be 11.2 cm because you lose only 0.3 cm of pressure with the wider tubing. To fix the problem you simply go into the menu ad change the tubing diameter to 22 cm.

But if you have a machine that auto-adjusts the pressure, it will deliver whatever pressure it figures you need

Dang it! I quoted.

I think this is close. The machines are designed to maintain pressure, and the flow rates we are dealing with, assuming there is not a large leak) should not affect the pressure through a 2-meter tube, even if we change from 15 to 22 mm.  I really do not know how the setting affects the machine algorithms other than a smaller tube will conduct pressure changes back to the machine sensor slightly faster than a 22 mm tube with higher volume.  I don't think "pressure drop" is actually the question, but rather the volume in the system. That is why we also have settings for full-face vs nasal or pillow masks.  It is the volume on the pressure side that is in question.  The volume of a 15 mm I.D. tube 2-meters long is 1413 cc and a 22 mm tube is twice as much at 3041 cc.  This air volume has a damping effect on air pressure from the blower to the user (changes occur a bit more slowly), but should not affect the actual pressure.  Kind of a cool geeky discussion here.

[OMyMyOHellYes]

Update: both the DME that shipped me the hose, and the one I originally got my machine from both say that the hose size does not make a difference.  But logically it would seem that it should make a difference because the volume of air is different when the diameter is either increased or reduced.

No, logically, hose size wouldn't matter.

Because fundamentally, you don't have a CPAV (Continuous Positive Air VOLUME) machine, do you?

No, I think you have a CPAP (Cointinuous Positive Air PRESSURE) machine of some variety.

And you see, in a closed system, pressure doesn't doesn't care about volume.  12cm H2O is the same pressure in the 15 mm tube as it is in a 19 mm tube as it is in a 22 mm tube. Or even a 44 mm diameter tube, if such a thing existed.

 That's why it doesn't matter.  Your machine uses pressure sensors to monitor and manage therapy, not the volume of air flowing thorough it.  And even if it were moniotoring volume as the determinant as to how much to pump, then that volume is only what you breathe in and what escapes through the vents, not what remains in the hose.  It has nothing to do with the diameter of the hose in any real sense.

It may have a very very tiny momentary impact on how fast the blower has to spin up to a pressure, but it is of no real consequence in the real world where you live.

I once had a very wise man describe this phenomenon as PAII - Preoccupation About Inconsequential Increments.  Getting distracted with stuff that just doesn't matter.  Like driving your car at 64.9 or 65.1 miles an hour in a 65 MPH zone for an hour long trip.  One is below and one above the speed limit.  Nobody is going to get pulled over for driving 65.1 and you are not going to get to your deestination more than a couple of seconds sooner.  64.9 is not going to get you to your destination but a few seconds behind when you would had you been driving at the posted 65 limit. There is a difference, but no real practical difference between them.

So in this regard what the DMEs are telling you is functionally spot on.