I don't get it!

[ThisIsMyUserName]

Ok, I'm thoroughly confused about why people with low pressures sometimes feel like they're not getting enough air. I've come up with and rejected two different hypotheses, and am on the fence on a third:

1) Not enough exhaust, and you're rebreathing CO2; I reject this because it seems like that would be a major flaw in general CPAP design, because the flow rates of air should provide amply new oxygen, and because sustained high CO2 rebreathing should have noticeable side effects that I haven't seen or heard about.

2) Not enough air in the mask (i.e. you breathe all the air out of the mask space before the new air comes in); I reject this because a) this should be the same as breathing low pressure air, which is the opposite of CPAP, and should result in apneas, which I don't see (I guess it's possible that the initial high pressure busts the apnea open and the later low pressure causes the feeling of suffocation, but I doubt it) and b) Again, the flow rates should more than compensate.

3) Psychosomatic (i.e. your brain freaks out because your nose is covered; you;'re getting enough air but don't feel that way); This doesn't seem right; the fact that I get the same feeling for nose pillows and nasal mask, which are so different, that covering my face doesn't seem to have the same effect, that so many people experience the same thing, and, most importantly, that high pressures (which don't impact the psychological aspect) alleviate the problem all speak against this.

So why is it? Anyone?

[chunkyfrog]

For me, it takes a certain amount of positive pressure to cancel out the closed-in effect of the mask.
The pressure also helps vent out the CO2 (see the little holes in the mask?) hey really do work!
It may only be that I am used to having a certain amount of pressure.
I understand that the mild air pressure helps splint open the airway, but since it only happens when I'm asleep,
I can't observe it happening.

[Julie]

Hi - you're correct on #2, but your rejection of that is not. It's just about not enough air (pressure) to open 'your' airway, however narrow it might be. And I'm having trouble understanding...

"should be the same as breathing low pressure air, which is the opposite of CPAP, and should result in apneas, which I don't see (I guess it's possible that the initial high pressure busts the apnea open and the later low pressure causes the feeling of suffocation, but I doubt it) and b) Again, the flow rates should more than compensate."

but we recommend raising the pressure because we're aware that the settings are too low... I think you're trying to equate breathing 'regular' air when awake to using Cpap when asleep, and you can't do that as the machine works with sleep-breathing (it can detect that), which is different to how you breathe when awake. I also believe that if your pressure's too low it won't stop apneas, but if you haven't seen any (at very low pressures) over whole nights - more than one or two - then maybe you should consider a new study. But Cpap doesn't 'burst' open apneas, it senses them building up (one at a time) and short circuits the effects by providing regulated air 'puffs' at enough of a pressure to compensate.

And I don't believe there's any psychosomatic component at all. Not the kind of situation it normally applies to.

[ThisIsMyUserName]

Julie, I think we're disconnecting because you're thinking about APAP and I'm thinking about CPAP; I use a very low pressure CPAP, but it's extremely effective. If I sleep even one night without it, I feel horrendous.

[Sheriff Buford]

In my opinion.... in #1, the CO2 has nothing to do with it. In #2, don't confuse pressure with volumn. You may have a set pressure, in your case 5-6, but your body senses there is not enough air in the mask and you appear to be responding normally. I firmly believe that in the cpap mode.... if your airway is sufficiently open at a 5 or 6, a 7 or 8 pressure will also keep your airway open at night. If you do bump up your pressure, watch out for centrals and see how you feel during the day. I would think the 7 or 8 would ease your sense of suffocation and allow you to sleep sounder.

[Rick007]

In my case I think it was #4 when I first started.

#4 The pressure from the machine opposes my normal exhalation. This opposition to normal breathing is interpreted by my brain as "difficulty in breathing" and resulted in the same feelings of anxiety as a reduction in inhalation would have caused.

In the beginning, I often opened my mouth so that I could feel the air rushing out. This action helped to reassure me that I had more than enough incoming air.

After a few weeks my breathing felt totally normal if I should happen to wake up in the middle of the night. When these awakenings occurred I ended up opening my mouth again, but this time to confirm the machine was still running.

[ekubaskie]

I think the psych issue wins in many cases. I've had the feeling myself sometimes when congested - so I plugged my finger into a pulse-ox unit which reported O2 saturation levels in the mid to upper nineties. I quit worrying about it and felt fine.

[SleepyBobR]

There's no physical explanation for the effect. I'm in the psychosomatic camp.

[zoocrewphoto]

In my opinion.... in #1, the CO2 has nothing to do with it. In #2, don't confuse pressure with volumn. You may have a set pressure, in your case 5-6, but your body senses there is not enough air in the mask and you appear to be responding normally. I firmly believe that in the cpap mode.... if your airway is sufficiently open at a 5 or 6, a 7 or 8 pressure will also keep your airway open at night. If you do bump up your pressure, watch out for centrals and see how you feel during the day. I would think the 7 or 8 would ease your sense of suffocation and allow you to sleep sounder.

This is what it feels like to me. Not enough volume as the mask is small (I need a small, so it needs to come in strong enough to keep it full and fresh. I start at 11 and I quit using the ramp after 2 nights. These days, the only time I have that suffocating feeling is if I have a coughing spasm. A single cough is fine, but when I start coughing multiple times, it feels like there isn't enough air, so the mask comes off.