Delivered pressure lower when using integrated humidifier

Hi, this is my first time posting here, although I recognize many of you from another forum.

I started CPAP treatment end of September, and have adapted well to use. However, my AI and AHI are still not where I'd like to see them, so I've been monitoring efficacy data daily.

When I first started using my machine, I attached the integrated humidifier but kept it at the lowest (unheated) setting. Although I was titrated with no humidification, it is pretty dry here and I do get dry mouth on occasion. While on vacation, though, we were in more humid territory, and more for convenience than anything else, I removed the humidifier.

My results seemed pretty good for being in a different hotel room every night, and my AI and AHI were trending in the right direction. But when I got home I reattached the humidifier - we had a cold snap and the forced air heat was running a lot. Almost immediately I didn't feel as good again, and when I checked, sure enough my AI and AHI were back up.

So I've done some experiments, and controlling all variables, there is a definite lower pressure when I use the humidifier. I don't have a manometer but I have very reliable Eustachian tubes - they noticeably close up quickly without the humidifier - and the AI and AHI results also tell the tale.

Has anyone else experienced this? Is this "normal"? I've Googled this topic but couldn't find anything. I will be calling ResMed but I thought I'd check here first.

I had a similar experience when I chose to leave my humidifier at home when I went on a trip. It seemed to me that there was more pressure without the humidifier. Also, my efficacy numbers were lower without the humidifier even though I didn't notice that I felt better during the day. I didn't sleep as well without the humidifier, so I do prefer using the humidifier. My doctor had to up the pressure to compensate so that my numbers are in the reasonable range. I feel great every day now with the combination of humidifier and higher pressure.

I find this an interesting thread. I have not really noticed this happening with my therapy but I do use just pass over humidity most of the time. As it gets colder here in Canada, I am setting the humdifier for a little heated humidity.

I don't use the integrated humidifier, except for travelling, but rather the F&P HC 150 Stand Alone humidifier. Since I haven't been travelling much, it's mostly the F&P humidifier.

Anyone else finding that their pressure is lower with heated humidity or even pass over humidity? Have people raised their presssure to compensate?

I just want to bump this thread and get more input! Thanks.

as an experiment to appease another forum member, I did the following - This was to determine if I needed to change my pressure if I had both HC 150 and integrated humidifier in my circuit.

pressures of 8. 12, 16. 20 - all were with the quattro on me and my water manometer in the line

humidifier options - A. HC 150 humidifier full, B. HC humidifier full and empty integrated tank humidifier, C. integrated tank humidifier only ------- in each case with water in it I was using the setting I would use overnight - I did not try both humidifiers full of water

machine options -- APAP tank and Pro 2 tank

I found some slight variances in pressure but nothing over 0.5 cm H2O, most within 0.2, and since they weren't consistently always high or always low in a setup run (first I ran all pressures with each humidifier and the APAP, then did it with the Pro 2) I attributed the variation to be just "white noise" and nothing to worry about.

I wonder if there's any connection to elevation above sea level? I know that sounds weird, but if you were e.g. near the ocean while away, you wouldn't have needed the humidifier, but if you returned to e.g. Colorado, you certainly would have (just examples, of course). Plus the temperature in your rooms might have been different as well, or the pillows (which can impact a mask), or maybe you just returned to your more usual sleeping habits in terms of time spent asleep vs otherwise.

pressure might need to be adjusted for the "cheaper" machines when elevation changes - like the Plus or the escape - these are things that muffy should be able to answer - oh cupcake muffin person???

however my experiment was all done at an elevation about 20 ft above sea level (if that high - got to consider that I had it set up on the kitchen counters not on the floor)

I'm twins with mreewh, as far as equipment is concerned, and I can't say that I've noticed either an apparent difference in pressure or a measured difference in efficacy between usage with and without the humidifier. I travel frequently, and I often skip hauling along the humidifier on short trips. It makes it easier to travel light and a night or two waking up with a dry mouth really doesn't bother me. In the last two months I've been in cities at sea level and the mile high city. I find a fair amount of variation in my AI and HI from day to day that simply seems random. This random element dwarfs any discernable pattern based on travel, for me at any rate.

Thanks Jules!

That was a very helpful experiment!

Mechanically, you'd expect lower total airflow when pushing the air through more "stuff". In my M-series, the air has to zig-zag around a bit, go through the labyrinth of the humidifier, then out the back. This extra friction will slow the air flow.

But what we are mostly concerned with is pressure, right? Less air flow means it takes marginally longer for pressure to build. In this case, it would surely be a fraction of a second. That shouldn't affect AHI, since auto machines adjust in minutes, not milliseconds.

As long as there is enough air flow to allow normal breathing, all should be well. I can't imagine that the extra friction of the humidifier path has a serious effect.

The reported change in AHI could be due to different pillows at different locations.

JimIllinois wrote:Mechanically, you'd expect lower total airflow when pushing the air through more "stuff". In my M-series, the air has to zig-zag around a bit, go through the labyrinth of the humidifier, then out the back. This extra friction will slow the air flow.

The air path through a Resmed H3i/H4i humidifier is short, and is not a labyrinth by any measure

Cheers,

Bill

Julie wrote:I wonder if there's any connection to elevation above sea level? I know that sounds weird, but if you were e.g. near the ocean while away, you wouldn't have needed the humidifier, but if you returned to e.g. Colorado, you certainly would have (just examples, of course). Plus the temperature in your rooms might have been different as well, or the pillows (which can impact a mask), or maybe you just returned to your more usual sleeping habits in terms of time spent asleep vs otherwise.

I do live at 7200' elevation, but my machine is supposed to auto adjust for altitude up to 8000+ feet. I considered that as well as the other factors you listed, so I repeated the experiment at home, eliminating as many variables as possible, and I still got the same results - apparent slightly higher pressure without the humidifier. I start a new contract job assignment next week, and I'm hoping to get access to a manometer and get some objective measurements.

Re batteries:

Beware that the absorbent glass mat battery is not sealed like the gel batteries, and has liquid electrolyte not a gel.

The AGM concept has a pressure relief valve that could open, though I expect that would only happen if charging it too hard at high temperatures (for $100. you can buy a fairly sophisticated charger these days, which should pay back its higher price in longer battery service life).

he batteries normally used in electric wheelchairs and scooters are _gel_ type not AGM, I think that’s what you should use if you want safety.

And in any case, I recommend a plastic catch tray underneath – a plastic stowage box for example.]

Sorry, moderator please delete the battery message and I'll post in the correct thread.

More passages, especially if rough and small, will theoretically cause some pressure loss since the machine is maintaining a pressure measured at a point upstream of the humidifier, tubing, and interface.

How much? Well, someone herein did the good thing and measured – finding negligible loss.

OTOH, I stumbled into a way to get more pressure loss, though I have no measurements – did not have the humidifier tube properly seated against the machine. Erps!