Longer hose cause pressure loss?

[ChipChris]

Does the length of the hose affect the pressure that you get? I know that in my fish tank, the longer the airline tubing that connects my air pump to my airstone, the less bubbles I get.

I wanted to hang the hose somehow above my head so I can move around easier but I dont think it's long enough.

[jules]

yes it can affect it - they say don't go over 12 ft but even before getting that long, the pressure is affected

check out these links and maybe you can find something there to use for an idea without lengthening the hose

viewtopic.php?p=89536#p89536

[ChipChris]

Fantastic, thanks!

[GumbyCT]

Does the length of the hose affect the pressure that you get?

The short answer is yes it does. The exact formula or calculation I do NOT have. Add mask leaks to the mix and it just confuses things more by preventing fewer (or no) events.

If you are using straight CPAP it is less of a problem bc you can increase the pressure to compensate for the loss. If you are using an auto it can miss some or all events and your software will make you think "life is good".

Last year I used a 10ft. hose then added an HC150 not thinking about the volume of the chamber or the hose. Later added an Activa Nasal mask which had another 2ft or so of hose. While my reports looked fine I noticed how I felt was not the same.

I now use nothing longer than an 8ft hose, but I am using an auto.

HTH,
GumbyCT

[Wulfman]

My answer is a little more complicated.....and based on my own opinions and what I've gathered from previous discussions on this subject here on the forum.
According to the manufacturers, it's not SUPPOSED to (affect the pressure), as long as you don' exceed about 10 ft. I don't recall hearing of any 12 ft. hoses, but I won't contradict my friend Jules on that one, and maybe if a person used a short one going to the humidifier and then used a 10 ft. one going to the mask, that would also be about 12 ft.
A straight-pressure CPAP machine that has "leak compensation" should be able to keep up the required pressure better than one that does not have leak compensation.
An Auto/APAP MAY have more difficulty detecting events at the longer distances.

All in all, I don't think that the loss would be significant, but there might be a tiny bit.
I DO have extra 8 ft. and 10 ft. hoses, but as yet have not had the "need" to use them, so I can't give any first-hand evaluations.

Den

[jules]

people make 12 ft from 2 of the 6 ft ones --

I have heard 10 and 12 both but I also know that adding the extra length of a hose off the mask to the 10 ft I use, does create havoc with the APAP mode when I use it

I think dsm or feeling_better might have some "real" data on pressure loss but I didn't search for it

shorter is better

[Goofproof]

The spec for the machines is 10 foot. Yes it does a little, but it's splitting hairs (Doesn't matter). Longer lengths may affect the APAP's ability to correctly sense the needed changes. I've never seen a problem using a 10 foot, as long as the APAP can sense what is happening, it will still get the job done. Jim

[Wulfman]

I did a search and found a significant number of threads on this subject. I've only picked 6 to post......however, the apparent limitations may only allow me to post two at a time.......so......

viewtopic/t37508/viewtopic.php?f=1&t=36 ... ss#p314036

viewtopic/t37508/viewtopic.php?f=1&t=32 ... ss#p278343



Den

[Wulfman]

More.....

viewtopic/t37508/viewtopic.php?f=1&t=31 ... ss#p271352

viewtopic/t37508/viewtopic.php?f=1&t=29 ... ss#p249999

[Wulfman]

Last two.....

viewtopic/t37508/viewtopic.php?f=1&t=22 ... ss#p195262

viewtopic/t37508/viewtopic.php?f=1&t=21 ... ss#p182537

[ChipChris]

Thanks everyone. I looked at all the really neat hose setups in those links and I do think I'll need a longer hose if I want to do one of those. I can get by with what I have but it does pull at my mask and I'm a restless sleeper.

I have a RemStar Plus M series cpap machine so maybe if I go 10 feet I'll be ok. I suppose I can always increase my pressure.
I think I'll look in my manual and see if there's any hose length recommendations.

Thanks again .

[dsm]

In a post last year someone found an official description of the pressure losses over a std hose in (IIRC) one of the Respironics clinical manuals.

Am sure someone else will remember the exact detail & manual - I'll probably recall the exact detail in a couple of days time

DSM

[Wulfman]

This is from the User's manual for the Pro 2:

Pressure Stability
4 to 10 cm H2O (±0.5 cm H2O)
>10 to 20 cm H2O (±1.0 cm H2O)
Measured in accordance with EN 17510 @ 6.6, 13.2, & 20 cm H2O @ 500 ml with BPM set to 10, 15, & 20 BPM
performed at 23° C (±2° C), 50% RH (±5%), and an atmospheric pressure of 101.54 kPascals.

Excerpts from the Pro 2 & Auto Service manual:

Static Pressure Accuracy +/- 1.0 cm H2O with no humidifier.

Pressure Drop with Humidifier 0.3 cm H2O @ 20 cm H2O

NOTE: Pressure accuracy measurements shall be taken at the end of a
six foot (1.83 m) patient circuit with a Whisper Swivel II exhalation
port connected to an Oxygen enrichment adapter that is
occluded. The manometer should be connected to the O2 port.


Den

[kopoloff]

I've been wondering about hose length myself. I looked in the settings menu of my S8 and it has a hose length function, but it only gives an option for 6 feet.

Seems to me there are a number of factors to consider.

If we add a humidifier, then we introduce a pressure drop into the system, but the machines seem to deal with this OK
I use a nasal pillows mask, which probably has greater flow limitations than a full face mask, so this is a pressure drop variation from setup to setup
In an ideal system, pressure drop increases with flow rate increase.
Pressure drop will vary with leak rate
The machines control pressure by varying flow rate (I'm pretty sure this is what happens)

Seems to me that if you have a CPAP machine, and you add a pressure drop into the system, then the effective pressure at the mask will fall. You will probably need to increase pressure slightly. An APAP machine on the other hand is monitoring flow rate variation - so it will be able to effectively increase flow to compensate.

I wonder though whether the increased volume if air will slow the responsiveness of EPR and *-flex systems? Then again, at the point where we start breathing out against the incoming air stream, the flow rate has dropped close to zero, so the pressure drop will be low at that point anyway.

My conclusion, after these musings, is that as long as we adjust pressure (on CPAP machines) then therapy should not be affected.

After this fumbling attempt to understand this mechanism has motivated me to find out more, so I will contact the Resmed technical support people and see what they say!

Cheers

K

[john_dozer]

Shooting from the hip, pressure drops in tubing of that diameter don't hold a candle to pressure drops from the holes in the CPAP mask.

The bigger problem is likely control. The more air volume you have in the system you could see one of two effects
1) The volume attenuates the pressure fluctuations in the mask back at the transducer and from the machine to the mask causing the machine to be less responsive in attempting to compensate for breathing
2) The volume becomes tuned to the frequency of breathing. Like an organ pipes of different lengths or like a pop bottle filled to different levels. This could actually amplify pressure fluctuations from breathing for all devices and confuse an APAP like crazy.