Higher pressure for longer hose?

Needsdecaf · Post by **Needsdecaf** » Thu Apr 24, 2008 6:47 am

Hello!

As some of you know by now, I have just completed my first week on CPAP, so far with good results.

I am creating a rig to hold my hose over my head so that I can move freely. I have designed it up and will be purchasing the materials today. Nothing too sophisticated and no new ground breaking designs, for sure.

In advance of this, I identified that the hose that came with the machine was too short. So I purchased a 10' hose that would allow me plenty of freedom. Last night I used it for the first time.

I THINK that I noticed a decent pressure drop to my face. Certainly an additional 50% of hose (2m to 3m) is a decent increase. When the machine first kicked on, my 8cm felt a little low, and when I put the ramp on, it felt like I was sucking in, rather than having air pushed in. Of course, I did still have pressure (pressure out the vents and coming out my mouth when open) but it seemed lower.

I should say that I woke up feeling crappy this morning, but I'm not sure if that's down to the fact that the mask started leaking around 3:30 and I took it off at 5:00 because it was annoying me. The extra length of hose was pulling on the mask.

Thanks!

DreamStalker · Post by **DreamStalker** » Thu Apr 24, 2008 7:10 am

A longer hose will add friction to the airflow and should have little effect on pressure ... pressure and airflow are not the same thing. Consequently, the added friction may affect the response of APAP machines but most likely not CPAP machines.

Taking the mask off and going back to sleep is why you wake up feeling like crap. Try harder to keep the mask on if you don't want to wake up feeling like crap. IMO, your body gets used to being treated well when under treatment, then you snatch the treatment away and the body is not able to deal with the trauma of O2 deprivation when you stop treatment. The treatment is very addictive to the body ... much like heroin but in a good healthy addictive way.

bdp522 · Post by **bdp522** » Thu Apr 24, 2008 7:22 am

Yep, what Dreamstalker said!

when I put the ramp on, it felt like I was sucking in, rather than having air pushed in.

Maybe try not using the ramp. At the very least set it higher. If you have to suck in the air, it isn't helping.

Brenda

TerryB · Post by **TerryB** » Thu Apr 24, 2008 9:42 am

I agree that the longer hose (going from 6 to 10 feet is 1.2M increase) will have a very small effect on the pressure at the mask. That's not to say that the pressure you are using is THE correct pressure in the first place.

Do you have the ability to monitor your results in the software?
Are you comfortable in "tweaking" the pressures.
I believe that you should observe the results for a week and if you don't feel good about things and/or see events in the software, tweak up the pressure by 1/2 to 1 cm and give it another week. I am up 2.5 cm from where I was prescribed 26 months ago, but I check the graphs every week and tweak as required. I do not run a longer than standard hose.

Good Luck,
TerryB

Needsdecaf · Post by **Needsdecaf** » Thu Apr 24, 2008 9:50 am

[quote="TerryB"]I agree that the longer hose (going from 6 to 10 feet is 1.2M increase) will have a very small effect on the pressure at the mask. That's not to say that the pressure you are using is THE correct pressure in the first place.

Do you have the ability to monitor your results in the software?
Are you comfortable in "tweaking" the pressures.
I believe that you should observe the results for a week and if you don't feel good about things and/or see events in the software, tweak up the pressure by 1/2 to 1 cm and give it another week. I am up 2.5 cm from where I was prescribed 26 months ago, but I check the graphs every week and tweak as required. I do not run a longer than standard hose.

Good Luck,
TerryB

Needsdecaf · Post by **Needsdecaf** » Thu Apr 24, 2008 9:52 am

[quote="DreamStalker"]A longer hose will add friction to the airflow and should have little effect on pressure ... pressure and airflow are not the same thing. Consequently, the added friction may affect the response of APAP machines but most likely not CPAP machines.

-SWS · Post by **-SWS** » Thu Apr 24, 2008 9:54 am

Needsdecaf wrote: Pressure and airflow are not the same thing, correct, but flow of fluid in any conduit will cause friction, and the friction will definitely cause a pressure drop. Trust me, I'm a Civil engineer and do this for a living.

Even if you weren't a civil engineer I'd trust your above statement since it's correct.

Needsdecaf · Post by **Needsdecaf** » Thu Apr 24, 2008 9:54 am

bdp522 wrote: Maybe try not using the ramp. At the very least set it higher. If you have to suck in the air, it isn't helping.

Brenda

To clarify, this was not normal before last night's switch to the longer hose. I have bumped my ramp up to 5 and felt fine when going to sleep. I am ALMOST at the point of not needing to use the ramp, but not quite there.

I didn't have any issues with the ramp pressure before the longer hose.

I'll try again tonight and see how it is. I think half of the problem was that I had the longer hose dragging on the mask, and it was annoying me.

DreamStalker · Post by **DreamStalker** » Thu Apr 24, 2008 10:17 am

[quote="Needsdecaf"][quote="DreamStalker"]A longer hose will add friction to the airflow and should have little effect on pressure ... pressure and airflow are not the same thing. Consequently, the added friction may affect the response of APAP machines but most likely not CPAP machines.

Needsdecaf · Post by **Needsdecaf** » Thu Apr 24, 2008 10:43 am

[quote="DreamStalker"]

Well I’m not an engineer nor have I ever taken a class in fluid mechanics but trust me, the change in pressure due to friction by going from a 6 ft hose to a 10 ft hose is “most likely” not going to be significant (relative to the accuracy of the blower unit). As an engineer I’m sure you can indeed come up with Reynolds numbers for the hoses and use Navier-Stokes to calculate the pressure differences between the two … but then why ask us if you need higher pressure for a longer hose?

Buy yourself a mamometer … or heck, you’re an engineer, just make one!

In any case, for effective treatment you need to keep the mask on whenever you sleep … yes that includes naps too.

Goofproof · Post by **Goofproof** » Thu Apr 24, 2008 11:13 am

DreamStalker wrote:
Needsdecaf wrote:
DreamStalker wrote:A longer hose will add friction to the airflow and should have little effect on pressure ... pressure and airflow are not the same thing. Consequently, the added friction may affect the response of APAP machines but most likely not CPAP machines.
Pressure and airflow are not the same thing, correct, but flow of fluid in any conduit will cause friction, and the friction will definitely cause a pressure drop. Trust me, I'm a Civil engineer and do this for a living.
Well I’m not an engineer nor have I ever taken a class in fluid mechanics but trust me, the change in pressure due to friction by going from a 6 ft hose to a 10 ft hose is “most likely” not going to be significant (relative to the accuracy of the blower unit). As an engineer I’m sure you can indeed come up with Reynolds numbers for the hoses and use Navier-Stokes to calculate the pressure differences between the two … but then why ask us if you need higher pressure for a longer hose?

Buy yourself a manometer … or heck, you’re an engineer, just make one!

In any case, for effective treatment you need to keep the mask on whenever you sleep … yes that includes naps too.

As Dreamstalker says, the longer hose will make a Small difference in flow, but the specs are designed to cover a 10 foot hose. XPAP isn't rocket science, even the machine has a pressure spec of 0.5 C.M Water Pressure plus or minus, and if you have and use the software, you can find the correct pressure you need for any condition.

Using the Ramp, expecially with the pressure to low is bad, not keeping the mask on, or leaks corrected, is much worse. Trying to split hairs over pressure drop from using a 10 foot hose is a waste of brainpower, the other things are the problems that need to be addressed. Jim

Guest · Post by **Guest** » Thu Apr 24, 2008 12:44 pm

DreamStalker wrote:...the change in pressure due to friction by going from a 6 ft hose to a 10 ft hose is “most likely” not going to be significant.

I agree with that statement as well. There will be a small pressure loss that really won't matter much. We have had multiple posters call manufacturer tech support throughout the years to receive that same answer Roberto just gave.

However, place your CPAP in the basement and run a 60 foot hose to your bedroom.... and all "good therapy" bets are off in my book! .

-SWS · Post by **-SWS** » Thu Apr 24, 2008 12:45 pm

The above was me guested yet again!

Guest · Post by **Guest** » Thu Apr 24, 2008 1:16 pm

Anonymous wrote:
DreamStalker wrote:...the change in pressure due to friction by going from a 6 ft hose to a 10 ft hose is “most likely” not going to be significant.
I agree with that statement as well. There will be a small pressure loss that really won't matter much. We have had multiple posters call manufacturer tech support throughout the years to receive that same answer Roberto just gave.

However, place your CPAP in the basement and run a 60 foot hose to your bedroom.... and all "good therapy" bets are off in my book! .

You also may have high radon levels being blown in with the air. Jim

RonS · Post by **RonS** » Thu Apr 24, 2008 1:18 pm

Boy, that sounded like "Trust me, I'm a lawyer." LOL

I added a standalone humidifier to my CPAP machine. It has a(nother) 6 ft hose, along with the water chamber. I noticed a definite decrease in pressure at the mask.

I didn't bother to test back and forth, the percieved drop was fairly obvious to me. Maybe when I go upstairs later tonight if I am not too tired I will do a sort of "side-by-side" comparison.

Since I am still working my way up to my prescribed pressure, I simply upped my pressure by 1cm to compensate.

Trust me, I'm a computer geek.