you dont really need that humidifier

[mstevens]

If you're using a nasal mask, and aren't mouthleaking, why would you need humidity more than a non-apneac? There shouldn't be more air flow.

Tidal volumes may not be higher than with a non-apneic, but flow rates are typically higher. Further, there's considerably higher turbulence due to increased pressure, so there are local air currents swirling around in the nostrils and sinuses. Higher flow rates and turbulence dry tissues faster than would otherwise be the case.

There is a very considerable amount of clinical data that supports the statements many people make here that they have greater congestion (which of course reduces the benefit of CPAP) when using non-humidified CPAP. The same is true of oxygen via nasal cannula, which in theory might not require humidification but in practice requires lots of it.

[chunkyfrog]

When we remove water from a floor, we use a fan to speed up the drying time--it really works!
We can also run the dryer on "air fluff', which also works faster than hanging stuff up indoors.
Likewise, my eyes get dry much faster if there is a fan aimed at my face.

[idamtnboy]

I've never tried not using the humidifier so don't know what it would like. But this one thing I do know. Since starting the CPAP with its humidified air I no longer have to dig dried up boogers out my nose. I just blow it a few times a day. Much, much, better condition!

[chunkyfrog]

Boogers; I kind of miss that.

[xenablue]

I grew up in Melbourne, Australia and can tell you that you have no clue about dry air. I now live in the U.S. midwest - balmy Wisconsin - and as soon as the cool weather hits, the air becomes filled with static electricity to the point where most homes have either a central humidity unit attached to the furnace or several humidifiers in different rooms.

I don't use my humidifier in summer, but even with our central humidifier running I use it in winter - without it I wake up with my nasal passages and throat like a desert.

I do agree with you - YOU don't really need that humidifier, but I can vouch for anyone in the U.S. (or other countries with dry, winter climates) who do.

Cheers,
xena

[archangle]

Tidal volumes may not be higher than with a non-apneic, but flow rates are typically higher. Further, there's considerably higher turbulence due to increased pressure, so there are local air currents swirling around in the nostrils and sinuses. Higher flow rates and turbulence dry tissues faster than would otherwise be the case.

Atmospheric pressure is 1000 cmH20. With CPAP at 20, there's only a 2 percent higher air pressure in terms of air density, turbulence, etc. Air flow and turbulence in the mask shouldn't affect the degree of turbulence in the back of your nose and throat.

I don't see why flow rates would be higher than a non apneac. (other than the 2% figure) Yes, there's more pressure forcing air into your lungs, but that pressure is resisting flow out of your lungs, so it should balance out after a breath or two.

I definitely agree we should always get a machine with a humidifier. Many of us mouth breathe, even if we don't think we do. I just don't understand the physics of why we would need it more than a non-apneac if we don't breathe through the mouth.

[mstevens]

Atmospheric pressure is 1000 cmH20.

1 atmosphere is about 1033.23 cmH2O. Close enough.

With CPAP at 20, there's only a 2 percent higher air pressure in terms of air density, turbulence, etc.

The percent difference doesn't matter. It's enough to be quite noticeable, since the baseline pressure is not at all noticeable to us. It does not take a very large column of water to make breathing completely impossible for humans; 40cm is enough to overpower respiratory muscles for lots of people. According to your example that's only about 4%. That's still enough to kill.

Air flow and turbulence in the mask shouldn't affect the degree of turbulence in the back of your nose and throat.

Ah, but it does, whether it "should" or not. Note, too, that I did not refer to turbulence within the mask but rather turbulence within the nares & sinuses.

Mask flow and turbulence certainly do affect what's going on in the nares. For a parallel, open your house door on a really cold, windy day. Is it fair to say that conditions outside the door do not affect conditions just inside it? No.

The primary point, though, is that flow rates ARE higher - that's almost unavoidable given increased pressures - and that turbulence within the airway IS increased (all the way to the lungs). The whole point of CPAP is to affect the anatomy of the airway (the famous "air splint"). It's impossible to titrate a pressure that restores absolutely normal anatomy through all phases of breathing. In reality, stuff is getting inflated. That changes airflow from normal. That's turbulence.

I don't see why flow rates would be higher than a non apneac. (other than the 2% figure) Yes, there's more pressure forcing air into your lungs, but that pressure is resisting flow out of your lungs, so it should balance out after a breath or two.

Connect a balloon to an air tank at 100 psi. Connect an identical balloon to a similar tank at 3,000 psi. Open the valves the same amount. Which do you think is going to fill its balloon faster? Greater pressure leads to increased flow rate.

Pressures in your airway are never going to "balance out after a breath or two". They are constantly-changing. Once they stop changing, you stop breathing. Inspiratory and expiratory pressures never "balance" each other out (as in your conjecture) because they happen at different times. Airflow is, of course, in completely different directions at those different times.

I definitely agree we should always get a machine with a humidifier. Many of us mouth breathe, even if we don't think we do. I just don't understand the physics of why we would need it more than a non-apneac if we don't breathe through the mouth.

Physics is important and the physics of this are understandable. What's more important is the biology. We're not glass tubes - we're complex organisms with anatomy that changes under varying conditions.

It used to be my job to teach physiology. My students were working from a foundation of university degrees with certain minimum backgrounds in physics, biology, anatomy, etc. It's beyond the purview of this board for me to walk someone through the physiological realities of the need to humidify CPAP (or ventilator, nor nasal cannula) air. In almost any other setting, there is no controversy at all about this need. I doubt you're just going to accept the weight of millions of patients' experience over many decades, but that's where I'm going to leave it.

If you don't want to use a humidifier, don't. If you find it helps, do.

[archangle]

see next post.

[archangle]

Actually, this does make sense if the increased pressure significantly increases the volume of air in your lungs at the top of the inhale cycle, and there is a feedback mechanism in your body that makes you tend to exhale to the same volume of air in the lungs at the end of the exhale cycle.

i.e. with CPAP, maybe the balloon inflates to a bigger volume on inhale, but your brain makes you squeeze the balloon down to the same minimum volume.

The mechanical "balloon inflation" effect IS based on the differential pressure between CPAP and non CPAP, not absolute pressure, so that effect could increase more than 2%.

[Captain_Midnight]

I got my first cpap 6 yrs ago, and with it, some very good advice from the folks at (the much-maligned Apria). Paraphrasing... "If you can use the machine comfortably without humidification, do so, as you will have a greater chance at success if you do so."

Several machines later, I rarely use my humidifier, and my AHIs are typically 0.3 or less, and I feel better than ever. I don't have to fiddle with d.i. water or worry about Legionnaires or other pathogenic microbes, rainout, and travel is much easier. Interestingly, the times that I tried humidification, my AHI actually increases as the heat setting rises.

Of course, this is not for everyone. But in my case, and I suspect a significant percentage of folks, no humidification is the way to go. (If you prefer the humidity, that's fine with me, I'm not going to say that my way is the better way for everyone.)


.