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Comment by nulagrithom | Hacker News Reader

Counter-anecdote:

My particular doctor shoots for an AHI around 10, which is still mild sleep apnea (5 is the threshold) and is still high enough to get you diagnosed and provided a CPAP in the first place.

So for 6 months my AHI hovered around 8 or 9, occasionally spiking to 12 (which made me really feel like crap).

My technician won't adjust without doctor's orders (and incidentally also told me I'd fry the entire machine in days if I used non-distilled water in the humidifier, which is just absurd.) The doctor books appointments months out, and is OK with my current results anyway.

So I tried bumping my pressure up by 1 and lowering the exhale comfort feature on my own. Tada! After a month my AHI averages 4, sometimes spiking to 6, and I feel much, much better.

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CPAP with humidifier user here. About nondistilled water:

My humidifier has a heated metal plate in the bottom of the tank. Its temperature is set on a humidifier scale of 1-8, plate temperature increases from 1-8.

Evaporation of nondistilled water will leave mineral deposits behind. Deposits decrease thermal conductance between heated plate and water. This will reduce evaporation rate, reducing effective humidity for a given setting.

If the control loop is smarter than usual and includes humidity sensing, there's a potential for thermal runaway. Doubt this is an issue, it's probably a simple temperature loop. I don't think you'd "fry the entire machine in days".

There may be more bacterial growth potential with nondistilled water. Don't know.

Using distilled water is a little less convenient, but could avoid some issues.

It's really not a big deal to use tap water, I did for years until I lost enough weight that my sleep apnea went away.

1.) Fill the tank with regular cheap vinegar to get rid of the mineral deposits. Maybe there is a problem with some tanks, but mine were all plastic or stainless steel and vinegar didn't seem to have any affect on them.

2.) Usually the tanks hold enough water for two nights, maybe a little more, at the settings I used them at. Dumping out the water in the morning kept the mineral content from becoming concentrated due to evaporation, and kept the buildup down to more manageable levels. If I didn't dump the tank every morining then I have rapid mineral buildup. I know it sounds silly, but it took me an embarasing amout of time to figure this out.

Once I worked out those two things I had no trouble with using regular tap water in the humidifier.

> Evaporation of nondistilled water will leave mineral deposits behind

This is true, but it will take weeks or months, depending on your water quality, and is easily cleaned if you know how.

Days in seattle

OK. I realize tap water composition vary.

I normally use distilled water, but if I'm traveling and don't have it handy, I'm not losing sleep over using tap water 1-2 nights.

Wow, that's insane.

My AHI during my sleep study was approx. 55-60 (It's been several years, forget the exact number).

With my machine my number is usually 1, most nights under 0.5.

(FWIW: Like you I found increasing the pressure a little and turning off all the 'comfort' features was the winning formula).

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