Central Sleep Apnea—A Simple Explanation

In sleep disorders, obstructive sleep apnea is the most common condition that’s seen, but a significant number of people with obstructive sleep apnea will also have central sleep apnea. Central sleep apnea is thought to be a condition that’s associated with a number of different neurologic problems, as well as heart or kidney failure. During the night, people with central sleep apnea stop breathing when signals in the brain that tells the body to breathe don’t work properly. No effort is even made to inhale. In contrast, with obstructive sleep apnea, an effort is made to breathe in, but because of collapse in the upper airways, air can’t get into the lungs.

One of the hallmarks of central sleep apnea is Cheyne-Stokes breathing, where after a long pause, due to gradually increasing levels of carbon dioxide (CO2), shallow breathing is triggered which gradually becomes deeper and deeper, and then once CO2 reaches a safer level, the breathing becomes more shallow again.

Unfortunately, treating central sleep apnea is more of a challenge than treating obstructive sleep apnea, and the best way of treating this condition is to use a variation of CPAP as a respirator. This is a servo-ventilator feature that’s found in machines that can treat this condition. When it senses that you’re not breathing, it literally breathes for you, rather than applying constant positive pressure for obstructive events. Some people will have a combination of obstructive and central events, which is called mixed or complex sleep apnea.

A number of different neurologic conditions can cause central sleep apnea, but here’s a simpler explanation:

We know that a HUGE number of people have undiagnosed obstructive sleep apnea. Up to 1/4 of all men and 1/10 of all women have it, and by the time you’re 60 or 70, the vast majority will have at least some degree of sleep apnea. If you’re human, and you can talk, then you’re susceptible to breathing problems at night, even if you don’t suffer from any apneas. The reason is that complex speech and language development unprotected our upper airways, and everyone’s tongue can fall back and obstruct your breathing at night, especially when you’re in deep sleep, due to muscle relaxation.

I’ve also talked about how modern humans’ jaws are shrinking, due to a radical change in our diets and the addition of bottle-feeding. This had lead to increased rates of dental crowding, with more and more people needing braces. The smaller the jaws, the less space there is for the tongue, which can take up too much space, ultimately crowding the airway.

We also know that there’s a linear correlation to complications of apneas, even in the very low range, where having an AHI of 4 is significantly worse than having an AHI of 2, although officially, you won’t have obstructive sleep apnea, since you come in below 5. Sleep apnea patients are also known to have thick or viscous blood that tends to clot easier when there are areas of low blood flow or small vessel constriction. People with obstructive sleep apnea by definition have smaller vessels and low blood flow simply due to the massive stress response that naturally constricts blood vessels and causes hypertension.

Numerous imaging studies also show that people with obstructive sleep apnea have much higher numbers of lacunar infarcts, which are small areas of dead brain tissue that’s normally seen in routine CT scans of the brain. Other studies reveal lower blood flow, metabolism and brain tissue density in certain critical parts of the brain that control memory, executive function, and autonomic function. Areas of the brain that address hearing, including the high frequency sound perceiving areas of the inner ear, are also extremely sensitive to instances of low blood flow or stagnation. One recent study showed that people with sleep apnea had lowered auditory brainstem reflexes, but after treatment with CPAP, or after thinning patients’ blood concentrations, these auditory reflexes improved.

One finding that’s fascinating is that parts of the brain that control breathing are also affected preferentially by these events. Knowing that even mild levels of sleep-breathing problems can aggravate various levels of clotting and vessel blockages, if you happen to clot off a small vessel that leads to this area, then your neurologic breathing patterns can be affected. These same areas also control autonomic function, which includes heart rate, temperature, digestion, sweating, and vascular reflexes. Damaging even a small part of the brain in this area can wreak havoc on your breathing patterns, as well as other regulatory functions that control your body’s organs.

Since we know that obstructive sleep apnea is strongly associated with heart disease, it makes sense that central sleep apnea is commonly seen in patients with heart disease. Not only can obstructive sleep apnea cause heart disease, by applying this model it can also cause central sleep apnea. Poor involuntary nervous system control, especially of the heart, can wreak havoc on heart function. It can also cause problems with digestion and even your hormones.

Although we have a way of treating central sleep apnea, the results are not as satisfying compared with treating obstructive sleep apnea. Ultimately sleep doctors don’t have very good answers to why this happens, or how to treat it effectively. Think of it as a permanent neurologic condition, where rather than having weakness of your lower legs, you have weakness of the nerves that control your breathing patterns. Treating the obstructive component probably won’t cure the central sleep apneas, but at least it could prevent it from getting worse.

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24 thoughts on “Central Sleep Apnea—A Simple Explanation

  1. A question:

    If a Resmed S9 Elite CPAP shows these data, does it indicate having central apnea?

    apnea index was 5.1
    AHI was 5.5
    obstructive 0.7
    central 4.8
    unknown 0
    hypopnea index 0.4

  2. hi I was just reading this artical and found this part to be interesting, i dont seem to be able to get answers from to many ppl and find i can afford a lot of professional help as im on a pension, I have OSD and also stop breathing so im told over 30times in an hr, i am over weight and have Bipolar, reading you artical there seems to be a lot in there that i have and am wondering if this is why i am not really responding to the cpap machine i have, when i was using it. the mask i was told suited me didn’t seem to after awhile as my moth started to open so i would breath via my mouth, i had a nasal mask, the head gear stretched out of shape and the nasil pillow wore out way to fast and as i said im on a pension so cant aford to replace things often. I have posted on yr wall as well,so if you put this together with that, it will save me tping everything all over again. Its just i find my concentration level has dropped so much i just cant do anything, i have other medical issues as well that i am happy to talk to you about, but please i need help, i dont know where to turn

    These same areas also control autonomic function, which includes heart rate, temperature, digestion, sweating, and vascular reflexes.

  3. Central Apnea is often consider a neurological problem but I am wondering if in some cases it isn’t a physical problem. There is a high incidence of Laryngopharyngeal Reflux Disease in patients with sleep apnea. I’m wondering if this reflux isn’t damaging or causing dysfunction in an central apnea patients chemoreceptors and there by disrupting the CO2 breathing feedback loop?

  4. Hello Dr. Park. I have the Resmed S8 Elite CPAP which dsplays onboard data following sleep. The combined AHI score when broken down consistently shows a MUCH higher HI score than AI score. This ratio is maintained whether ther overall score is high or low. For example if the AHI = 8.9 it shows HI = 8.7 and AI = 0 .2 Likewise if the AHI = 5.0 it shows HI of 4.9 and AI = 0.1 Before treatment, my polysomnogram apparently showed a score of 39 events, with sustained periods in which my oxygen levels dropped to 71% During my titration overnight study done using a BiPAP machine, the sleep doc said my oxygen level was improved and was between 90 – 95% for 88% or more of the time, and prescribed a CPAP machine. I told him that I sometimes wake up aware of the fact that I need to breathe in, but seeming unable to do so ALTHOUGH feeling no great sense of urgency that compels me to do so (no gasp for air). He said it just seems that way to me, but I do inhale, I just think I don’t ! My question is “Does the great discrepancy between my HI and AI scores indicate that I have Cental Sleep Apna (or mixed sleep apena) ?

  5. Ms. Dent,

    It’s more likely that your pressures are adequate for your apneas, but not strong enough to get rid of your hypopneas. If you had central events, either your diagnostic sleep study and sometimes your CPAP machine (in some models) can tell you if you have central events. I wonder why you were titrated on a BiPAP machine and given a straight CPAP. It sounds like you need to talk over this issue with your sleep doctor and try to get your HI as low as possible. Good luck.

  6. Hi there I have sleep apnea. I use a bi pap machine but I now have acid reflux when I sleep. Can this machine be causing the problem? I tilted my bed 8 inches, no eating or drinking after 6pm and watching everything I eat. Can you help me?

  7. over several years [maybe 10] I have had several asthma test, [spirometer]? that I have failed, even after a puff of inhalent. Went to Jewish Nat. for test, the only thing out of the ordinary of regular ashma was when they tried to draw my blood while on a exercise machine, they could not set up the cath. my blood clotted three times on each arm. Fast forward a year I had surgery to correct a problem from having five kidos and in recovery they discoverd I had a PE . My family Dr. and I were wondering if maybe I was having PE’s all along, looking at some kind of thick blood diagnosis. Also have had very low energy and been treated for depression off and on(more on) for years. Reading your articles opens up anoth er avenue?

  8. Suzy,

    Sleep apnea is known to cause thickened blood, depression and low energy. Pregnancy can sometimes aggravate sleep apnea due to weight gain. A sleep study is something you may want to consider, given your history, especially if one or both of your parents snore heavily.

  9. Hi,
    The intiall study in the hospital gave 10.6 AHI. I was strongly asked to sleep on the back, what I did not like. I snore only if I sleep on the back (according to my wife). I was sleeping only for couple of hours, had very bad night of sleep.
    The following study included sleep machine and I was almost unable to sleep at all.
    They said that “they managed to pump some oxygene in my lungs.”
    I have been told to use S9 auto (Resmed) with settings 4-20.
    In the last three weeks there was no a single night where AHI went over 5. It is around 2, typically.
    My stomach is full of air and this machine caused sickness (I am very sensitive on the cold air) pumping cold air in my lungs, without warming it first, as it is normal in breathing.

    The hours I sleep with machine were less then I normally sleep.
    Finaly, last night I removed the machine and had a long night of sleep tryinjg to recover from the flu partially caused by the machine.
    The doctor insisted on using on S9 auto machine which cost 2500USD here. I asked him about using DeVilbis and he was extremely rude saying that I do not support local industry.
    I also lost around 8 kg since the initial study.
    In other words, I believe that I do not have sleep apnea. I feel good and was foreced to do a study, but that is a separate story.
    Would appreciate your advice.

  10. If you strongly suspect UARS and have been given the chance to use the CPAP machine approximately how long does it take to adjust to the CPAP machine with nare pillows (respironics) . If someone can not adjust to the machine – what should they do next?
    Is Bipap better for UARS?

  11. Ms. Richard,

    If you use CPAP and the compliance data shows that everything is essentially normalized, you should know within a few weeks if you’re going to feel better. Sometimes, it can take months. However, UARS patients tend not to tolerate CPAP as well as people with OSA. BiPAP has been advocated for UARS by Dr. Krakow, but mainstream sleep doctors have no formal recommendation on this. Ultimately, it other options depends on your upper airway anatomy. Some people do better after nasal breathing optimization (surgery), and others do well with mandibular advancement devices. Advanced orthodontics are another option.

  12. Connecting some dots:
    Wrong breathing pattern = = > huge breaths while sleeping
    Huge breaths while sleeping = = > CO2 drops
    When CO2 drops to one’s apnea threshold = = > breathing stops
    Breathing stops = Central Sleep Apnea

    “When a patient becomes apnoeic, CO2 produced in the tissues, accumulates in the blood at a rat of about 5mm Hg per minute” (Medical CO2 canisters safety information)
    Once CO2 accumulates just over one’s apnea threshold = = > breathing is resumed
    Since the person’s breathing pattern is not optimal – the whole things happens again
    And again
    And again

    Coming out of this loop is possible with breathing training,
    & the Buteyko breathing methods does EXACTLY this.

    So, there’s an explanation
    There’s a solution

  13. Dr. Park
    I am in a very difficult position. I feel like my health is falling apart bit by bit. And, I do believe it starts with my long term sleep problems. I am so tired I feel like I am losing perspective and my productivity is dropping more and more each week. Having been diagnosed with Obstructive Apnea 12 years ago I tried a cpap (3 times now) and struggle with claustrophobic feelings and, the pressures. Due to that I use a dental appliance which stopped the snoring issues but I continue to struggle with nightly events. Since moving back to the US my Doctor has tried to get an overnight sleep study arranged but United Health will not approve because their “expert” does not see any need. We have attempted approval 4 times. They will only suggest I home sleep study. I truly believe I have a central/complex apnea. My wife tells me I often have shallow breathing and, I wake up multiple times “out of breath” with other physical attributes (I am embarrassed to say it here) that will subside when I sit up and take in deep breath and exhale with force. In listening to you and reading the information I need to find a way to get this diagnosed and dealt with. I am actually beginning to worry that a without doing so a major event is coming soon. Can you help? Could I visit your office and arrange for a sleep study location you know can diagnose Central/Complex apnea. I can’t wait for the insurance company and, I am ready to sell assets/borrow money to get this cleared up. Sorry for my rant but I think I am desperate.

  14. I’ve heard about sleep apnea, but I never knew about it in depth. So this was really interesting! I didn’t know that there were different kinds of sleep apnea. I also didn’t know that “humans’ jaws are shrinking” and that it’s effecting our breathing! Thanks for this enlightening information!

  15. Mr. Wilson,

    Sorry to hear about your health issues. In my experience, you’re better off starting with a home test first, and then trying to get an in-lab study arguing that there’s a suspicion for central apneas or other unusual issues going on. The insurance companies have to follow a strict protocol. In the end, they will have to spend more money and waste people’s time, but that’s the system that we have.

    Unfortunately, I can’t give you any recommendations without formally examining you first. I’m happy too see you for consultation in the future. Ideally, you should try to arrange for an in-lab study before you come to see me.

    Good luck.

  16. I have a Resmed and played with the settings for 7 months and still averaged around a 10 AHI. Out of desperation, I stuck in my old oral appliance. Immediately my AHI dropped to under 1.0. I was able to reduce my pressure significantly and get excellant results.

  17. I switched to the ResMed Auto BiPap and have dramatically reduced obstructive apneas, hypopnias, snoring and flow limitations according to my Sleepyhead reports. However, it has created 1 to 2 central apneas per hour and I still have symptoms. My goal is to have less than three, 15 sec or less events every night.

    I read Dr. Thomas’ article below where he shows that adding 50 – 100ccs of rebreathing volume to the circuit may prevent excess CO2 loss which likely drives CPAP induced centrals. Insurance denied a sleep study at Dr. Thomas’ clinic so I am planning to modify my nasal mask by moving the vent 75 ccs down the line. I assume if I need more O2 I will open my mouth.

    Is it reasonable to believe that adding a rebreathing volume will lower centrals?

    Also, what do you think of the ECG-derived sleep spectrogram as a way to measure sleep quality vs EEG? I’m looking for a device I can use at home to measure sleep architecture and arousals. This is too important to leave at the whim of insurance companies.

    doi: 10.1016/j.jsmc.2013.10.008
    Alternative approaches to treatment of Central Sleep Apnea

  18. Hello my son is 14 just diagnosed with central sleep apnea has about 4-5 events a night even with his machine on. We have a pretty high tech machine which is being monitored by a team online as well but it’s pretty nerve racking don’t know to much about it I know more about obstruction apnea, his sleep doctor was shocked when he seen his report and called us right away his blood gas was very high and this was his second study, is it normal to have events while still on a machine? And can it eventually go away?

  19. I am scheduled for a heart ablation for AFIB in about 10 days. I postponed it once already because I was introduced to BiPAP late December 2017. I could not tolerate CPAP but now I am seeing very good data with the BiPAP and my AFIB episodes are much reduced. I am still on the beta blockers however. I am just wondering about during the ablation is it crucial to go after the “third Fatty Pad” on the heart. Also there is talk about remodeling taking place on the heart after successful treatment of sleep apnea. Have you any comments on this? I have posed these same questions to my heart Doctor, but no answer yet. I’m told I should still have the ablation anyway because AFIB will come back even if the Apnea is being treated. I just don’t want to do the ablation if waiting for more sleep apnea treatment time may actually stop my AFIB. BTW my initial diagnosis over 20 years ago was obstructive sleep apnea. Did they even know much about central back then?

  20. What is the difference between being diagnosed with central sleep apnea and central events? I also have obstruction sleep apnea and use a CPAP to treat it.
    Thank you for your time.

  21. Judi,

    A central apnea is an event during a sleep study when there is no breathing effort detected on your chest/abdominal leads and no airflow in your mouth/nasal channel, as described in the article. A central sleep apnea diagnosis is when the majority or all of your events are central in nature, as opposed to obstructive.

  22. Dr. Park, you’ve had guests on before that talk about chronic daytime hyperventilation and how it lowers baseline CO2 stores. We know that CO2 levels in the blood are responsible for delivering oxygen from the blood to target tissues.

    Could it be that a central event is the body’s way of raising lowered CO2 back up to an optimal level where O2 can then be delivered optimally?

  23. Hello Dr. Park, very interesting article. I have OSA and have been recently diagnosed with a Hiatal Hernia. My question is do you think my OSA aggravated my H. Hernia?
    Thank you very much.

  24. Mr. Martinez,

    Actually, routine apneas can create tremendous vacuum forces in your chest cavity, potentially sucking up your upper stomach into your lower chest cavity.