Difference between central and clear airway apnea

[Rcgop]

I am sure this is wrong on many levels but it works for me.

My sleep test was a 50-50 split between OA's and HA's with zero "central apnea". Once I started therapy, the OA' and HA's virtually stopped and my AHI dropped to 4 on average with a few nights in the 11-12 range. 90 percent were CA's (clear airway apnea).

Central apnea are where the brain fails to send the signal. In my case, I felt so tired just fighting the machine that the brain did send a signal. The signal was to just take a break because your just too tired of breathing.

This makes more sense as 90 percent of my CA's in the last 4 hours of the night. With them becoming more frequent as the night went on.

Once I got comfortable awake or asleep with the machine, every thing cleared up.
Last night 8 hours good sleep and AHI .3 with total 1 HA and 2 CA.

To quote Trump "I'm just sayin".

[Sleeprider]

I think is comes down to semantics. If you stop breathing for any reason for 10 seconds, with what the machine detects as an open airway, a CA is scored. If you are asleep and the autonomic breathing is in effect, it really makes no difference what cause you attribute to the event. It just is what it is, and many new users experience this more frequently as they adapt to the therapy. It often goes away on its own without any intervention.

[Rcgop]

I agree with sleeprider. However, I fear centrals, Where as I can better accept clear airways, if I use my explaination above. I am just strange that way.

[Sleepster]

This is called CPAP-induced central apnea. The conventional wisdom is that, due to the CPAP therapy, the blood oxygen level is higher than it was without CPAP therapy. It's low blood oxygen levels that trigger breathing, so that trigger is absent. Usually the body adjusts to the higher oxygen level and the problem goes away. It's part of the adaptation process.

CPAP machines determine central apneas in a way that's not as reliable as the methods used in a sleep study, so those detected by CPAP machines are often referred to as clear airway apneas to make that distinction. The nice thing about software such as SleepyHead is that you can use it to see how long these clear airway apneas last. Mine are usually between 10 and 12 seconds, which is very short.

In my case, clear airway apneas are induced by bi-level therapy, so I have to keep my pressure support low at about 4.4 to keep that under control. Also, when I tried using a heated hose for a couple of nights when I had a cold, it induced them!

[Rcgop]

Thanks Sleeprider,
That is a much better explaination than mine and makes more sense. I was looking at my SleepyHead reports and found a lot of similar wave forms, just not long enough to register. I guess I am getting more accustomed to the pressure. This is very encouraging news.

[robysue]

This is called CPAP-induced central apnea. The conventional wisdom is that, due to the CPAP therapy, the blood oxygen level is higher than it was without CPAP therapy. It's low blood oxygen levels that trigger breathing, so that trigger is absent. Usually the body adjusts to the higher oxygen level and the problem goes away. It's part of the adaptation process.

The trigger for breathing is actually the CO2 level in the blood, particularly when we're talking about sleep breathing.

And it's not completely understood why some folks have a more difficult time regulating their CO2 level during sleep for a short period after starting CPAP. If I recall correctly, the usual theory is that some people tend to breathe deeper or more often when asleep and using CPAP than they did pre-CPAP. Either of which can lead to slight hyperventilation, which in turn can cause you to blow off a bit too much CO2. And that in turn depresses the brain's ability to send the "breath now" signal to the lungs and diaphragm to inhale, which results in the CPAP-induced central apnea.

As Sleepster has earlier said, for most people the problem goes away on its own: The body adjusts to the new new and as part of that adjustment it learns to deal with the new normal situation, including the slight change in CO2 levels. Once the body adjusts to CPAP, it correctly responds to the new levels of CO2 in the blood.

[0rangebear]

[quote='Sleepster' pid='162150' dateline='1463410263']
And it's not completely understood why some folks have a more difficult time regulating their CO2 level during sleep for a short period after starting CPAP..........................................
The body adjusts to the new new and as part of that adjustment it learns to deal with the new normal situation, including the slight change in CO2 levels. Once the body adjusts to CPAP, it correctly responds to the new levels of CO2 in the blood.

Interesting point, I am wondering if this could also be why people who make large and frequent changes to their settings; find their AHI going up, even when they return to their original settings

[palerider]

> Difference between central and clear airway apnea

if you do a fair amount of searching on the net, you'll find that "clear airway" is a phrase that respironics coined for the condition of not breathing and not having your airway blocked.

everybody else in the industry calls that condition "central apnea".

if you google "clear airway" -respironics about the only hits you find are on boards like this with people wondering what the difference is.

[eseedhouse]

> Difference between central and clear airway apnea

if you do a fair amount of searching on the net, you'll find that "clear airway" is a phrase that respironics coined for the condition of not breathing and not having your airway blocked.

everybody else in the industry calls that condition "central apnea".

Well I think that in this particular case it's Respironics that's right and "everybody else" is wrong. No machine that doesn't have electrodes pasted to your scalp can definitively say your apnea is "central", which means caused by the central nervous system and (IIRR) in particular your brain stem.

Any machine that just senses just air flow can only know that (1) an apnea has occurred and that (2) the airway was probably clear. This is not enough to be certain that the event was a true central apnea, one caused by the central nervous system. Sure it's fairly likely that "CA" events are actually central events, but a machine that measures only air flow cannot reliably say that.

So good medical practice is to not lable events "central" unless it is certain that they are. And a machine that only reads airflow cannot provide that certainty.

[richb]

Hypopneas are often converted to Centrals for people using xPAP machines. For some people a sleep study will show a lot of Hypopneas and some Obstructive events. If the Hypopneas are obstructive in nature then adjusting pressures (titration) will work using traditional CPAP/BiPap. Some people in addition might respond to the CPAP therapy with spontaneous Clear Airway/Central events. These often go away by themselves or with minor pressure changes. Other people with primary Central Apnea/Periodic Breathing present with a slew of Hypopneas and maybe some Obstructive events during a sleep study. For these people traditional CPAP therapy converts the hypopneas to Clear Airway/Central events. No machine adjustments will make these go away. For them an ASV machine is the only thing that works. People rarely present with pure Central events during a sleep study. Those that do so are often suffering from complicating illnesses such as Congestive Heart Failure and other sometimes life threatening illnesses. A problem for diagnosticians is that it is very hard to tell one Hypopnea from another. It seems that the best way to differentiate Central Apnea/Periodic Breathing from Obstructive events is by using an advanced data capable CPAP/BiPap machine. Such machine will convert the Hypopneas to Centrals instead of clearing them up.

Rich