AirSense11 temperature regulation

[Lostsleep]

TMA, keep us informed. I should be getting my new tube this coming week. I feel like a kid waiting for Christmas, LOL. I will let you know what happens.

[ThinMountainAir]

Hi LostSleep, I regret to say it may be a lost cause. You’re correct that having a ClimateLineAir 11 hose will give you access to the Climate Control feature but DogSlobber is correct that it won’t achieve what you want it to.

I took a lot of temperature readings and got basically what you did, though not as high. I researched more about the machine and now I believe it’s not a manufacturing or design defect but intentional. ResMed has said this, though perhaps not specifically about the 11: “The HumidAir™ heated humidifier will rise to a target temperature of 40°C [85º F] over 20 minutes. The device then holds this temperature for a further 10 minutes, ready for therapy to start.” Changing settings with my ClimateLineAir 11 couldn’t couldn’t get the output temperature, as measured with household thermometers in the airflow coming out of my nasal mask, any lower than with a standard hose.

That’s obviously what most people want, nice warm air. But it’s not what you and my friend wants. So what to do about it?

My first thought was to bypass the heated-even-when-off hotplate. To do so required some MacGyver-jury rigging but nothing too complicated. The air going into the reservoir comes out of a hole that is 3/4 of an inch in diameter. Standard vinyl tubing is available in ODs of 3/4 inch. That helped. Instead of 77º, which was the maximum I got before, the air got no higher than 75º when my room temperature was about 72º. I don’t know where most of this above-ambient heat is coming from. Some may be coming from the hot plate despite being bypassed because it warms up, even if slightly, the entire device. And some heat is coming from the blower motor.

In earlier posts we discussed the blower motor as a possible source of the unwanted heat. We were both of the opinion that a motor that small wouldn’t produce heat of any significance. The machine is fed by an AC to DC transformer with an output of 65 watts available for both the motor and the hotplate. I assume most is for the hotplate but I nevertheless tried to calculate the heat produced by the motor. There are calculators on line, no math required. What I found was beyond my training in physics (high school, final grade D-) but it did seem that time was a factor, ie, the longer a motor ran the more heat it produced and even tiny motors produce a lot. If I was using the calculators correctly, even small motors produce enough heat to fry an egg. But then I thought, I guess that’s if the heat stays there and isn’t dissipated. And the next thought was, how is the heat from my little CPAP motor dissipated? The answer, in my non-physics mind, is that it’s like a VW’s air-cooled engine but with the heat blown into the hose going, ultimately, to the mask.

Like the majority of users, the heat of the output air doesn’t bother me. If it did, and if I wasn’t concerned about voiding my machine’s warranty, I’d take it apart a look to see if would be easy to disconnect the power to the hot plate and, if so, I’d do that. If that looked like more than I wanted to get into, I’d make the hot plate by pass permanent. That, too, I’m sure would void the warranty. The vinyl tubing coming directly from from blower hole would have to be made secure, the end of the vinyl tubing attached to the hose would require finding the right fittings, the final project would look like a Rube Goldberg device, and even then it might not result in a temperature as low as desired.

I’m sorry to be the bearer of bad news but there’s a possible bright side: I could be completely wrong. If your new ClimateLine hose gets the results you want, or if you come up with some other solution, please let me know.

[ThinMountainAir]

I just read this post by Dog Slobber, responding to settings regarding mask type: "I also *believe* the mask setting is important for other therapy responses and measurements. For the exact same reasons why we must also enter tube size (standard/slimline/3m(AirCurve)). Detecting and measuring things like Apneas type (FOT), Breath triggering, and leak measuring are influenced by resistance and air volume in the system."

I'm sure the same would apply to my idea of bypassing the hotplate with a piece of vinyl tubing. That should have occurred to me. Maybe that D- in high school physics was deserved.  On the other hand, maybe the feedback system isn't that sensitive. It doesn't seem to matter, for example, whether or not there's water in the reservoir, which is a pretty big change in available volume. Then again, maybe the ResMed company assumes one will always use water. And maybe buried deep on the clinician guide it says something similar to what it says about supplemental oxygen:  “Adding oxygen may affect the delivered pressure and the accuracy of the displayed and reported values.” 

[Dog Slobber]

I took a lot of temperature readings and got basically what you did, though not as high. 

The inconsistencies in the OPs temperatures, heater plate high when the heater plate was off and low when the heater plate was on are explained by his use of an IR thermometer.

IR thermometers cannot be used on reflective surfaces. The heater plate being very reflective and the hose potentially being slightly reflective.  When IR is used against reflective surfaces the temperature is influenced the angle and the distance / temperature of the item the IR light is reflected upon.

I've demonstrated this in the same application.

The top pic:

• Heater Plate Off
  
• Room Temp: 76.3 (F)
  
• Plate Temp via digital thermometer: 77.2 (F)
  
• Plate Temp via IR thermometer: 80.2 (F)
  

The bottom pic:

• Heater Plate: Setting 1
  
• Room Temp: 76.5 (F)
  
• Plate Temp via digital thermometer: 89.6 (F)
  
• Plate Temp via IR thermometer: 83.8 (F)
  

The digital thermometer was placed at the centre of the heater plate. The IR thermometer was *very* susceptible to variance dependent on distance, angle and where it was pointed at. I pointed at the center, close to where the digital thermometer made contact and made considerable effort to ensure the distance and angle was consistent between reading.


FWIW, I performed the same experient against the side of my stainless steel electric water kettle. Which has a surface not unlike the heater plate. Similar results the digital thermometer measured temperatures much closer to the boiling point of water, with the IR thermometer considerably lower. Dipping just the tip of the digital thermometer into the just boiling water measured it at 212 (F).

[Lostsleep]

>>IR thermometers cannot be used on reflective surfaces. <<
Thanks for that piece of information. I wondered why I had such a large spread in temp readings when "shooting" the plate. I used a best guess average of the readings.

[ThinMountainAir]

Dog Slobber, thanks for checking those temperatures. I re-did my testing. Room temp was 71. With the heat and temp settings OFF, I put my three household thermometers in a paper bag, put the CPAP hose in the paper bag, and put a blanket over the paper bag. Why? I don't know. I guess just trying to create as best I could the temp of the air a person breaths from the machine, without influance from the ambient air (other than the machine's intake).  Before, with the thermometers merely in front of the air coming from the tube, I got only about 77 .

This time I got 85. But not right away.  After about 15 minutes it was up to 75. Then I left the room and didn't check again for over an hour. At what point in time it max'ed out, I don't know. Pretty sloppy study. But the delay in max heat might explain why my friend says he starts out ok but wakes up "in the middle of the night " in a panic that he's being suffocated. 

But the solution? Beats me. Isn't the Airsense 11, and maybe the 10, supposed to be a big improvement over earlier CPAPs not only because of auto titrating but also because the heated, humidified air is so much more pleasant (for most people)? If that's so, then isn't the solution to just use an older style device?

[Dog Slobber]

I've got a few machines at hand, I'll do some air/tube/plate temperature checks.

Won't be able to get to it for a few days, but I am interested.

[ThinMountainAir]

I've got a few machines at hand, I'll do some air/tube/plate temperature checks.

Won't be able to get to it for a few days, but I am interested.

Thanks, Dog Slobber, I look forward to it. I'm glad you're interested. I find this to be a puzzling challenge that's getting frustrating and i'm very close to giving up.  
 
Meanwhile, I have a new theory. After all that testing of the hotplate and of the output air, and the air by passing the hotplate, it turns out that it's the blower motor that's producing the heat. I'm pretty sure that when the hot plate is Off it's Off and the heat is coming from the blower motor. I realize it's just a little motor, but it does produce heat and that heat has only one place to go: into the face mask, or, in my crude experiment, into a paper bag, where it got up to 84. But the hotplate, as you and I and Lost Sleep measured it, is only 77.  Can either of you try this: aim your IR thermometers at the plastic inside the cavity where the reservoir  tank goes?  Maybe even inside the hole to the blower motor? I don't know if you can aim an IR thermometer into the hole at the spinning blower fan, but close?

[Lostsleep]

OK, after a 20 minute run time with humidity set to OFF, I had a tube outlet temp of 87°F. The temp shot at the impeller was between 87 and 92°F, depending where it IR is pointed.
About the outlet of the hose temp - I insert a digital thermometer about two inches into the outlet of the tube with the mask removed. I do not know how you could get a more accurate reading than this. The measurement would be the same as what is in your mask.

[ThinMountainAir]

It seems pretty clear to me that the heat is coming from the motor and no where else. I like how ResMed makes the best of it, as though it was intentional and it's such a good thing the trademarked it The HumidAir.

As I've said, the hot air doesn't bother me. In fact I'm surprised it's so hot. But it bothers my friend so I told him about this forum and the temp readings and discussions of the source. As to what he could do about it, I didn't have much to say. He has already been putting ice in the water reservoir. I don't know if he's tried turning the on humidifier on the thinking that if the air is going to be warm anyway, maybe warm humid air would be less unpleasant than warm dry air.  I suspect that he hasn't, that if the air is to warm then turn off everything that could be causing heat. 

The only ideas I had was, in addition to ice cubes in the water reservoir he was already doing, to place an ice pack in front of the machine's air intake port.  And maybe also aim a little desktop fan at the machine itself. This latter suggestion was based on the fact that some of the motor's heat is absorbed by the rest of the machine as made clear by the high temperature readings you and Dog Slobber got from the hotplate even though it was turned off. 

My friend said he implemented  my suggestions and they helped  a lot. But I don't know if he was just being polite.