Can using a longer hose necessitate a pressure change?

Further tests tonight if time permits.

I will try the same tests with the PB330 Knightstar set to cpap mode. Also will dig out a Remstar Plus as I know it has no output transducer & is easier to set the pressure on thann a HC221LE.

The PB330 has an ancillary ais sensing line. I'll try to add an extetension to the ancillary line for the 10' hose.

Also I may do a couple of the tests using other masks (hybrid & breeze or CL2)

DSM

DreamStalker wrote:
Test results may also be flawed due to location of testing. Down Under, fluids flow the opposite direction, from fluids north of the equator. The spiral wrap of the hose, may effect the flow due to the spin factor. One location the flow would spin, with the spiral, the other would have to jump over the wire, and would waste more energy. Jim

Indeed. This is due to a force called the Coriolis force.

Wiikipedia wrote:An air or water mass moving with speed subject only to the Coriolis force travels in a circular trajectory called an 'inertial circle'. Since the force is directed at right angles to the motion of the particle, it will move with a constant speed, and perform a complete circle with frequency f. The magnitude of the Coriolis force also determines the radius of this circle:

.
On the Earth, a typical mid-latitude value for f is 10−4 s−1; hence for a typical atmospheric speed of 10 m/s the radius is 100 km, with a period of about 14 hours. In the ocean, where a typical speed is closer to 10 cm/s, the radius of an inertial circle is 1 km. These inertial circles are clockwise in the northern hemisphere (where trajectories are bent to the right) and anti-clockwise in the southern hemisphere.

If the rotating system is a parabolic turntable, then f is constant and the trajectories are exact circles. On a rotating planet, f varies with latitude and the paths of particles do not form exact circles. Since the parameter f varies as the sine of the latitude, the radius of the oscillations associated with a given speed are smallest at the poles (latitude = ±90°), and increase toward the equator.

So the next question, dsm, is how fast does the air flow down the hose, at what latitude were the measurments taken and did you observe any anti-cyclones while you were making these measurements?

John M
(tongue in cheek and no longer blocking airway)

I have been reading the various posts or opinions, I use a 6ft. hose at home.

In my Motorhome if I place my machine on the shelf where the TV goes, I use my 10ft. hose. If I set my machine on the floor by the head of the bed in the Motorhome I use the 6ft. hose.

I have talked to Apria (dme from hell) and asked about a longer hose and they gave me a song and dance that the hose was by prescription sounds like bovine excrement to me.

I started getting my supplies from cpap.com, asked about the hoses and they said I could even connect 2 hoses together and they sent me an adaptor for the 2 hoses.
They say there is no loss of pressure due to linking two hoses together or the lenght of the hose unless they come apart. IMHO they sell them and they should know.




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[quote="Patrick A"]I have been reading the various posts or opinions, I use a 6ft. hose at home.

In my Motorhome if I place my machine on the shelf where the TV goes, I use my 10ft. hose. If I set my machine on the floor by the head of the bed in the Motorhome I use the 6ft. hose.

I have talked to Apria (dme from hell) and asked about a longer hose and they gave me a song and dance that the hose was by prescription sounds like bovine excrement to me.

I started getting my supplies from cpap.com, asked about the hoses and they said I could even connect 2 hoses together and they sent me an adaptor for the 2 hoses.
They say there is no loss of pressure due to linking two hoses together or the lenght of the hose unless they come apart. IMHO they sell them and they should know.

Tonight we went visiting guests so no further tests BUT, it occured to me that all the prior tests were done without a humidifier in the circuit. So, I need to do a few specific tests to measure the effect they have & after seeing CMS go up when the mask was attached, I am no longer willing to predict what putting a humidifier in the cicuit will do.

Theoretically it should have no effect on the mask end readings & the blocked tube readings. But, it may change the machine end data.

DSM

Nite all (but your morning )

Because these tests are so extensive I'll post different tests as I do them & can then gather the data into spreadsheets later. Also they will be easier to digest.

Test 1 using a Invocare Polaris ISP 9800 (flying Saucer) Cpap (worked out how to change the pressure again) ...

http://www.cpapwholesale.com/invacare-polaris-cpap.htm

(PS - this machine acts like it has a pressure transducer & I see in the above link they say it has one so this adds a variation from using the Healthdyne Quest that I don't believe does have a transducer. Also, notice below that the CMS did not jump when I put the mask on (no breathing), but stayed the same compared to just blocking the hose).

*********************************************************
Cpap set to 16 CMS

6' hose - blocked -
Manometer at the machine end - cpap led says 16, manometer says 16.
Manometer at the mask end - cpap led says 16, manometer says 16.

12' hose (2 x 6')
Manometer at the machine end - cpap led says 16, manometer says 16.
Manometer at the mask end - cpap led says 16, manometer says 16.

SUMMARY 1:
Static (no airflow) pressure shows pressure equal at all points.

********************************************************
With UMFF Std mask attached - no breathing (but allowing fixed leak venting)

Cpap set to 16 CMS - 6' hose - no breathing
Manometer at cpap end - Cpap led = 16 - Manometer says 15.75 cms
Manometer at mask end - Cpap led = 16 - Manometer says 15.25 cms

Cpap set to 16 CMS - 6' hose - breathing in
Manometer at cpap end - Cpap led = 15 - Manometer says 15 cms
Manometer at mask end - Cpap led = 15 - Manometer says 14 cms

Cpap set to 16 CMS - 6' hose - breathing out
Manometer at cpap end - Cpap led = 16 (spikes to 17 ) - Manometer says 16 cms
Manometer at mask end - Cpap led = 16 (spikes to 17 ) - Manometer says 15.5 cms

SUMMARY 2:
The 1st figure (15.25 & 15.75 ) indicate a friction loss of .5 due to venting alone.
When breathing in, the friction loss grows due to faster air flow (& greater friction)
and this is even more obvious in the 12' tube below.
================================

Cpap set to 16 CMS - 12' hose - no breathing
Manometer at cpap end - Cpap led = 16 - Manometer says 15.5 cms
Manometer at mask end - Cpap led = 16 - Manometer says 15.0 cms

Cpap set to 16 CMS - 12' hose - breathing in
Manometer at cpap end - Cpap led = 15 - Manometer says 15 cms
Manometer at mask end - Cpap led = 15 - Manometer says 13* cms

*(this figure of 13 varies greatly depending on how I breathe - if I nose breathe it
only goes to 14, if I mouth breathe at what I believe is a slow rate (sleep) it goes
to 13, if I breathe at a modest deep rate it drops as far as 12, if I breathe really
deeply it drops to 11. I believe reflects the variation in pressure loss due to the
friction in 12' of tubing & due to faster air flow as breathed air volume increases)

Cpap set to 16 CMS - 12' hose - breathing out (modest rate)
Manometer at cpap end - Cpap led = 16 (spikes to 17 ) - Manometer says 16.0 cms
Manometer at mask end - Cpap led = 16 (spikes to 17 ) - Manometer says 15.5 cms

SUMMARY 3:
Breathing out doesn't seem to vary the manometer very much - typically only by 0.5
even if I vary the way I breathe out (faster & slower). It is breathing in that has
the most notable impact.

DSM

More tests later

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CPAPopedia Keywords Contained In This Post (Click For Definition): hose, tubing, manometer, CPAP

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CPAPopedia Keywords Contained In This Post (Click For Definition): hose, tubing, manometer, CPAP

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CPAPopedia Keywords Contained In This Post (Click For Definition): hose, tubing, manometer, CPAP

you are doing a lot of testing I might suggest stay at 6 foot and 10 foot as that seems to be th question the 12 foot might throw the results out

Anonymous wrote:you are doing a lot of testing I might suggest stay at 6 foot and 10 foot as that seems to be th question the 12 foot might throw the results out

I plan to only do the next tests with 6' & 10' but the value of the 12' hose is in showing the trend that the longer the hose the greater the losses.

Now, you are more than welcome to add some tests - there are so many I want to try - for example, I believe using a Hybrid mask will show greater cms loss with the mask on and no breathing losses due to its much greater vent rate than the UMFF.

I also want to do a set with 10' and 6 using a CL2 mask. I suspect the results will be quite different to a hybrid.

So if you want to take on any segment & do those tests, pls advise

Tks

DSM

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Ill get my 2 cents in. I agree with John that pressure drops more in a longer hose of the same diameter.
Fluid flow (Gas) follows the perfect gas law pv=nrt and it also follows conservation of energy or bernule's law sp?. It says that if fluid flows from point 1 (machine) to point 2 (mask) that the energy at point 2 equals the energy at point 1 minus the energy loss from point 1 to point 2. Energy is mainly pressure head + elevation head + velocity head. The energy loss from flow is mainly friction loss which is proportional to the length of flow among other things so a ten foot hose will have 10 / 6 times as much pressure loss as a 6 foot hose at the same velocity. The pressure head v2/2g decreases to compensate for the friction loss so with a ten foot hose more pressure is lost than with a 6 foot hose. A system that senses pressure at the nose would be better. Compressible flow is more complicated.

I do not know if this will help.

GeneS

[quote="GeneS"]Ill get my 2 cents in. I agree with John that pressure drops more in a longer hose of the same diameter.
Fluid flow (Gas) follows the perfect gas law pv=nrt and it also follows conservation of energy or bernule's law sp?. It says that if fluid flows from point 1 (machine) to point 2 (mask) that the energy at point 2 equals the energy at point 1 minus the energy loss from point 1 to point 2. Energy is mainly pressure head + elevation head + velocity head. The energy loss from flow is mainly friction loss which is proportional to the length of flow among other things so a ten foot hose will have 10 / 6 times as much pressure loss as a 6 foot hose at the same velocity. The pressure head v2/2g decreases to compensate for the friction loss so with a ten foot hose more pressure is lost than with a 6 foot hose. A system that senses pressure at the nose would be better. Compressible flow is more complicated.

I do not know if this will help.

GeneS

Something that would effect pressure loss more than hose length is flow velocity. Friction loss is proportional to velocity head which is v(squared) / 2g. So if your mask is leaking and the flow doubles, the velocity doubles, and the velocity head is four times more. The friction loss would be four times as much when flow doubles a six foot hose is like a 24 foot hose when flow doubles. I do not know how the machines compensate for this but I assume they try to.

GeneS

[quote="GeneS"]Something that would effect pressure loss more than hose length is flow velocity. Friction loss is proportional to velocity head which is v(squared) / 2g. So if your mask is leaking and the flow doubles, the velocity doubles, and the velocity head is four times more. The friction loss would be four times as much when flow doubles a six foot hose is like a 24 foot hose when flow doubles. I do not know how the machines compensate for this but I assume they try to.

GeneS