Condensation and pressure

[ozij]

On a different thread "Guest" posted the following:

Also, even minor amounts of condensation in the hose can cause drops in the pressure.....the actual reading on your machine will not change but the pressure inside your mask or nasal interface can drop up to 6 points

I've been wondering about that.

Do the droplets make the pressure less? If so, does that mean than on an auto I will have less effective pressure --> more apneas --> higher pressure reading on the machine to achieve the results it would have reached without the droplets?

I have also noticed that on my PB420E and Breeze combination, with a maximum pressure of 9, when the condensation is high I will hear rude noises coming from where the narrow hose connects to wider one. And I even find moisture escaping there. Does that sound familiar to anyone?

O.

[Guest]

The doctor showed me a new study that was just completed that had the office in quite an uproar. There are older studies around, you can read many of them on the internet. The new study was done specifically with autos. For example: constant pressure setting at 10..small amount of condensation will lower the pressure in the nasal interface up to 1 point. The machine will still read 10. The more condensation that you are getting in the hose, the more the pressure that actually reaches the mask will drop. The worst case scenario is when you are actually hearing the gurgling in the hose......it can drop the pressure reaching the interface up to 6 points...which puts the pressure you are receiving at 4. Now remember, the machine....auto, fixed, bi, whatever...is not capable of reading the pressure in the mask. The CPAP cannot make any changes, so it stays fixed. The auto, will react to the noise in the hose, and may actually spike the pressure. Also, if the pressure reaching the mask keeps dropping, you will start to suffer hypopneas, flow limitations and apneas, which then results in increased pressure spikes. My doctor has notified all their patients to keep the hose "wrapped", elevate room temperature to prevent condensation and, at the very least, arrange the hose so that it feeds DOWN into the machine and does not form any low spots in which condensation can form. They are not presently recommending the heated hose...they are not against it....they just will not recommend it until they personally test it out to see if it causes any variances in the way the machines react. They have always freely prescribed the auto, and are still prescribing the auto, but they are questioning the effect of CFLEX on pressure levels. They are conducting a 3 month study of their patients using CFLEX, and the differences that may or may not be caused by CFLEX. Their concern is, for some individuals, a minor drop in pressure, could cause an apnea, thus making pressure levels continue to rise. They have sent orders to all their DME's to do weekly downloads of cards......I am certain the DME's are happy as clams. I am being one of their lab rats and have just finished a week with CFLEX on 3, I will now go to 2 for a week. You must not alter any of your equipment while doing this....which means sticking with 1 nasal interface....a real PIA because I switch frequently...so I chose carefully!! Personally, I happily joined in the study because I WANT to know the positive and negative impacts of any equipment I am using. Hope this helps.....I will be getting a copy of the latest study soon so I can read it in depth. I was really quite pleased that they were concerned enough to notify patients of the consequences and actually sent letters AND had the DME's contact patients. Of course, as usual, the DME's are clueless. One thing I have learned from this board is to be proactive. I thing I have not learned from this board is to sign in.......no matter how many thousands of times I push that ignorant remember me button....it never works! 2 listless

[JL]

2Listless

Would sure be interesting to know the impact of condensation on pressure at the interface. At present I don't have obvious condensation problems (rainout) but it could be more subtle. I stopped using CFlex for the reasons you mentioned but don't have enough data to confirm it. Derek I believe was going to run test on himself to get more data. Sure would like to see your Doctor's study results when they're available.

Jim

[Fifi]

2LIstless I too would be very interested in the results of your trials. Will you post the results, please?

[ozij]

Also, if the pressure reaching the mask keeps dropping, you will start to suffer hypopneas, flow limitations and apneas, which then results in increased pressure spikes

Hmm, I have a hunch I sleep better with less condensation, but I never took the trouble to record it..., I just lowered the humidifier. Sleeping in Jerusalem, with an open window makes setting the humidifier a real challenge - some night are nice and cool - my car looked rained upon early this morning, just because of the dew - and other will be hot and desert dry... I did order the HH though - and am waiting for it. Your letter has made more aware of the need to choose the setting for the humidifier before I go to sleep.

By the way -

Now remember, the machine....auto, fixed, bi, whatever...is not capable of reading the pressure in the mask

The 420E actually is capable of that - the PB auto has a special pressure-sensing very narrow little hose, threaded through the regular one. It's connected to the machine on one side, its other end is inside the hose, near the mask, on the other.
Which is not to say that it can't be thrown off kilter by all that extra humidity...
O.

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): 420E, humidifier, hose, auto

[Guest]

For those of us who have been singing the praises of what this board has affectionately nicknamed the "Aussie Heated Hose" (actually called the SleepZone Heated CPAP Tube) this is interesting news. I knew it ended the annoying rainout, but had no idea the rainout could have such an adverse effect on my treatment. Nice to know my money was spent wisely for improved therapy and not just comfort!

SleepZone Heated CPAP Tube

[Maskedmechanic]

CPAP.com has a video that shows the effects of water in the hose on cpap pressure. Here is the link https://www.cpap.com/downloadVideo.php?VGID=16

Bottom line... Water in the hose seriously compromises CPAP therapy.

[Guest]

I knew it ended the annoying rainout, but had no idea the rainout could have such an adverse effect on my treatment.

I'm not convinced about all of this... I think that if your hose, based on the way it is draped, had a 'valley' in it such that the condensation built up enough to block the tube, forcing the air pressure to have to push through the water trap, this could throw off the ability of a non-420E machine to sense what is happening with the user.
(Given that the 420E has a sensor line that measures pressure at the mask, rather than at the machine, the 420E would not likely be thrown-off in it's ability to sense patient pressure need.)

However, the build-up of water would, I believe, have impact upon delivery of treatment pressure as the movement of water in the tube would make for some gurgling and, some ebb/flow of air pressure. In essence, the user would get less than consistent air flow.

In a non-420E machine, I think pressure delivery could be thrown off by condensation in the tube even if the tube was not fully occluded. I think a 420E, thanks to it's separate pressure sensor line, would properly sense pressure being delivered and would be able to identify what the user needs at the mask, and deliver appropriate pressure even though there is significant condensation in the line. If the amount of condensation in the hose was huge, such that the hose was occluded by a water trap, I think the mechanics of the air pressure needing to push it's way through the water trap would make for poor air pressure delivery.

[WillSucceed]

Arrrrrgggghhhh!!!! Got guested!
That last post was me.

[Guest]

The physical mechanisms leading to condensation is ALWAYS caused by a significant lowering of the air pressure and thus, the temperature of the air and any water vapor present in the air. If the ambient air is sufficiently humid, the drop in temperature is enough to cause water vapor. A vapor barrier can be placed at the point of highest vapor pressure.....the inside. However, a vapor barrier in this type of physical system would cause a further loss of pressure by dispersing water molecules, causing a change in density and hence continuuing to lower the pressure. Condensation is the temperature to which air can be cooled by evaporating water into it. When it is close to the air temperature, it shows the air is close to being saturated....you CANNOT evaporate moisture into air. When the air is saturated, it cannot hold anymore water vapor...hence condensation. Saturation occurs when there is equilibrium between evaporation and condensation at a certain temperature and the liquid water surface is flat.

If air is exposed to changing temperatures, the air will be driven from an area of higher partial pressures to an area of lower partial pressures. In a cool column of air, the molecules are closer together, so density is greater and the change in pressure is greater. Pressure levels will be highest at a particular height (in this instance, length). In a warm column of air, the water molecules are farther apart, so density is less, and the change in pressure, as you go up, is less. So vertical pressure also becomes less. Water molecules always affect pressure.

The Bernoulli Equation = pressure becomes smaller within the vortex.
A vortex is formed, the swirl component of velocity causes the velocities to become considerably larger than the surrounding flow. If ambient air is sufficiently humid, the low pressures and temperature will cause water vapor to condense. Vetical pressures are directed from high to low against gradient force.

Simpler explanations: Watch a faucet, hose or any liquid being poured, as the liquid leaves the say, faucet, if you watch carefully the water is swirling...it has formed a vortex....the outer edges have higher pressure than the inside. Think hurricane.....vortex, inner area, no presure (the eye), outer edges, high pressure. So simple physics...inside a hose, a vortex is formed.....it is not a straight powerful flow....obviously, they want you to think that.......depending on the density of air molecules, the pressure levels will lower either a small amount or there will be an extensive drop.

Regarding the hose in question, having never seen one, I do not know what type of transducer is inserted into the hose. However, the "sensor" is still measuring pressure in the hose....not in the mask. The only way to adequately measure presure inside the mask is to insert a specific device inside the mask to measure the pressure. My best guess, would be the mask end of the hose is measuring force of exhalation against velocity. I quickly looked at pictures of various masks, the pressure in the mask will lower simply because the human body gives off a significant amount of water through respiration. Unless the airflow, respiration and water vapor are all at a constant level, condensation should also form in the mask.

Conclusion: Pressure in humidifier is not equal to pressure in hose is not equal to pressure in mask. Physical dynamics will alter it at each step. Without tearing apart a machine, looking at the components, analyzing the computer chip and programming, it is impossible to determine what they are using as measures to alter pressures from the machine. You need a computer expert to remove the chip and analyze it. I am not that person.

I posted this in response to a request from a "friend" who can identify herself if SHE so chooses!

Regards, Lang

[dsm]

I just posted this link in reply to 1 of Kenny's posts re the Aussie heated tube.

My comment was that I expect manufacturers to start adding heated hoses. F&P have in their new HC604 ...

http://www.talkaboutsleep.com/third_tie ... _HC604.htm

Cheers

DSM

[Metron9]

We have an air compressor hooked up to a 16 foot 4 inch iron pipe. (at work not driving my cpap ) As the air rises to the top of the pipe and cools the water condenses on the sides and runs back to the bottom of the pipe.

Why not make a small version of this idea by feeding the air from the cpap to a 4" x 1 foot thin stainless steel or copper or plastic pipe. Leave enough room at the bottom for the water to condense out and pool up, drain it in the morning.

Or a device that measures the level of condensation and automatically bleeds the water off.

It's really a matter of getting the temp of the air from the cpap to room temp BEFORE it enters the tube that goes to the mask thus eliminating the condensation INSIDE THE TUBE.

Also would allow you to breathe COOL air instead of heating the air up to Tropical rainy season temps. I live in Minnesota and I like my air temps at night in the 60s, The warmer the air the more water it holds but you can still have 100% humidity in 65 degree air and your lungs won't feel like a wet blanket.

[chrisp]

Then why have a humidifier if you want to remove the moisture. As for the original post. Water in the hose actually caused my auto to increase the pressure. It thought I was snoring.
That was with a 420E And my old Spirit.
Thats why I got the aussie hose.

:twis ted:

[2listless]

The way I am reading it and I read it about 15 times until my brains were sucked up into a vortex, you not only want humidity but you need humidity but at a certain point too much will make condensation and then all that other "stuff" happens. So condensation lowers the pressure, as does, hose length, a nonintegrated humidifier and evidently, a million other variables. Also, the pressure coming out of the hose, is swirling around, so the pressure must not even be equal in all parts of the "swirl" and as it hits other variables in your mask, such as breathing, moisture, warmer or cooler air...the pressure can alter again. Wonder what happens if there is heavy breathing?

Did have a followup appointment at the sleep center today....took in 2 weeks worth of downloads....quickly comparing my results using Activa, Comfort Curve and Vista, CFLEX on 3 and integrated humidifier set on 2 (would like it off because it is tooooo hot), the differences were quite astounding. The biggest variant was the integrated humidifier this time around. My Remstar Auto with CFLEX and FP humidifier gave snore index in the high 20s and low 30s with pressure levels from 7 up to 12. 12 is my top setting so when I hit that level it was pretty much a lot of flow limitation and hypopneas. With the integrated humidifier, the snore level dropped to a high of 7 and a low of 3. The pressure ranged from 5 to 7.5. I had 5 entire nights that the pressure level ranged up and down from 5 to 6 like a little decorative stitch. They hopped all over that and were trying to compare it to breathing patterns and the drop in pressure with the CFLEX. So then, I had to go the pulmonologists office and have breathing pattern tracings which were then sent to the sleep center for comparison. Won't really know anymore until I return in 2 weeks. This go around the CFLEX is being lowered to 2. As far as mask comparisons, the Activa gave me the highest pressure readings and the highest AHI, the Comfort Curve was the next lowest and the Vista was very lowest. The CC and the Vista were really close numberwise. I had already known the Activa was giving me elevated numbers...not sure why...except that I find it exceptionally warm and heavy, even after chopping half of it off. Oh yes, the hoses are all wrapped.....just what I need something warm and fuzzy in bed with me when it is 100 degrees. Bless the AC!
And now we are off to Chicago to spend 2 weeks with our children and grandchildren. Will be back just in time for the next appointment. Maybe Chicago's lower altitude will alter my Tennessee readings. Nothing would surprise me anymore!

[Guest]

<<<Then why have a humidifier if you want to remove the moisture. >>>

You don't understand, You only remove the moisture the air can not hold. If air at 98 degrees holds 1/2 lb per cf and air at 68 degrees holds 1/3 lb per cf both are at their saturation points and will not dry your throat. The second reason is I like to breath cool humid air instead of hot humid air so i want the air at 68 degrees to hold as much water as it can so my throat wont get dry from the cpap machine but not so much as to condense in the tube supplying the air. A larger Humidifier without heat could do the trick (keep the air temps constant) or an auto adjusting heater and array of moisture sensing equipment could work, but I tend to think saturating the air at a higher temp (heated humidifier) and cooling the air back to room temp allowing whatever condensation drain out is less expensive and is a simple device to make.
I will try it and let you know how it works,

A simple box on the floor with a connection to the supply and feed tubes would also allow condensation to run down the hose to the floor box as well but I would like to keep the inside of the hose from condensate if at all possible.