High AHI's in Mexico City

[Sleeprider]

Doing an internet search on the terms "altitude central apnea" I found that is is a real phenomenon https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227706/

This study demonstrates that central apnea becomes significantly more common at increasing altitude in both diagnostic and treatment portions of split-night polysomnography in patients with significant OSA. An apparent exponential increase in the percentage of OSA patients with a CAI > 5.0 occurs with increasing altitude. Altitude associated central apnea has a significant negative effect on the quality of OSA treatment obtained during PAP titration for patients living at the altitudes addressed in this study.

Also this advise from Denver Dental Sleep Care:

Altitude induced apnea or central sleep apnea is a disorder in which the breathing invariably stops and starts during sleep. The low oxygen level at altitudes directly affects the sleep center of the brain resulting in disturbed sleep, decrease in total sleep time, reduced sleep efficiency and sleepiness throughout the day. CSA is the condition of irregular, periodic breathing during sleep and it occurs because the brain fails to send across right signals to the muscles involved in breathing during sleep. As the oxygen levels are low, the oxygen sensors in the body signals the brain to increase breathing (hyperventilation) which in turn, leads to increase in oxygen and decrease of carbon dioxide in the body. The low carbon dioxide levels then send across signals to the brain to stop breathing to cover up the low CO2 levels and thus, breathing stops for about 12 seconds and resumes again taking in more oxygen. This results in an irregular pattern of breathing causing trouble sleeping.

CSA differs from another common form of sleep apnea known as obstructive sleep apnea (OSA) in which breathing is affected due to some obstruction in the upper airway passages.

So, clearly we have some people that frequently visit high altitudes, and are affected by central sleep apnea there, while being adequately treated at lower elevations.  It's hard to know how to advise on this as we should consider the frequency of visits to high altitudes and severity of the problem.  No doubt our data-capable CPAPs and BPAPs an make us aware of the problem and its severity.  It would seem like a good idea to consider ASV therapy if the problem is bad enough to cause serious fatigue or dysfunction, or presents a health risk.  In my opinion a sleep study should be considered very cautiously as few facilities can provide the high altitude environment which causes the condition, and a sleep study may not be necessary if you have machine data that can be used as a surrogate.  In addition a titration study would be useless unless it was conducted at similar altitude(s) to where you visit or live.  Unless you spend a significant portion of your life at this altitude, I doubt insurance will pay for the ASV, and you may be far better off looking at online suppliers and the gray market for substantial discounts. 

FWIW, there is nothing wrong with owning an ASV if you don't have chronic central apnea.  I know of a number of people that run these machines like auto bilevels and CPAPs.

[C0mbe]

Just to add to your post sleeprider:

Most of the sleep docs in Denver are well versed in altitude induced complex Apnea.  Mine in particular uses the high-altitude sleep lab in Frisco (9000 ft) when folks present OSA in Denver, but live in high altitude or visit frequently.  

It used to be that people would visit Denver for a sleep study and it would not reveal the severity of the complex apnea becuase it's only 5280 ft.  Of course, insurance would refuse an ASV because they were fine in Denver, and the patient would return home and suffer. According to my doc, 6000 ft is the magic number where OSA begins to present as complex apnea in people prone to altitude problems.  

I was born and spent most of my life at sea level and I am much more affected by altitude than my wife who grew up in Denver.

[Sleeprider]

Good follow-up C0mbe. I am aware of high altitude pulmonary edema (HAPE) and that is a major concern for people not acclimatized to altitude, when they go over 8000 feet. I was not aware that altitude also played a role in CSA, but I guess I am now. I guess you either avoid altitude or get the equipment that lets you live there healthfully. Oddly enough, as I said earlier, I seem to do better at altitude.

[C0mbe]

I think it's very unique to the person. I know a few folks on APAPs and Bi-levels with no issue at altitude, and some who do. I would consider yourself lucky! Prior to starting PAP therapy, my sleep at higher altitudes was an order of magnitude worse than at home in Denver with plain old severe OSA. I love skiing, so that has been a problem, but I'm slowly educating myself and it's getting easier to sleep at high altitude!

[Sterling147]

Thank you for all the feedback. I have been monitoring my AHI's since my return to NYC from Mexico City. My first 2 nights were low 9's, next 2 nights were low 5' and the last 3 nights were low 2's. I was getting up to 15.31 AHI levels in Mexico City in February and March. I am scheduled to see my sleep doctor on April 13, pending the availability of oxygenation  test result. We will look at patterns between NYC and Mexico City. If my current pattern of low AHI's, and centrals continue in NYC I will bring up the possibilities of bipaps (he already mentioned the possibility) and asv's for Mexico City as I will probably be living there for the next several years. If my AHI's remain low here, I also don't see the sense in a titration, or perhaps even a sleep study in NYC, as I would seem to be covered here. I don't know if my insurance would cover a sleep study in Mexico City, which might make the most sense. I just have to ask how accurate and reliable are the SleepyHead readings.

[Sleeprider]

The only place you could take a sleep study that would make sense is the one in Frisco, Colorado mentioned by C0mbe. Just FYI. If you are spending years in Mexico DF, then I suggest you start searching Craigslist, other forums and online providers like Supplier #2 (SecondwindCPAP) for either a Resmed S9 VPAP Adapt, Resmed Aircurve 10 ASV or Philips BiPAP Auto SV Advanced. Getting a prescription should be a simple matter of discussing this with your doctor and sharing the study referred to earlier. It is very unlikely you will be insured. Be aware a simple bilevel / BiPAP will not work and could make your problem at altitude worse.

[Sterling147]

I will discuss this with my doctor and let him know about the article. I doubt that I will be able to go to Frisco for a sleep test, but I might try to arrange for. One in Mexico City, if it would be covered. I will discuss the advantages of the asv in relationship to the article and see if it might be covered.Do any asv's algo function as bipaps or cpaps?
Thanks again

[Sleeprider]

C0mbe, another interesting thing I noticed from my data; at altitude, my tidal volume drops by about 20%. For me, that means a reduction from 650-720 mL to 450-570 mL. I can't explain the reduction in volume with identical BPAP settings, but it sure would make an interesting study hypothesis. Consider if you and others with CA at high altitude have no change in tidal volume at altitude, it would have the same effect as a high pressure support on bilevel, where CO2 is reduced and centrals occur; while an individual that does not experience CA at altitude compensates by reducing ventilation volume.

Purely speculative, but it sure would make an interesting study. Have you ever observed tidal volume and minute vent difference at altitude vs lower elevation?

[C0mbe]

That's very interesting, and certainly would make an interesting study. I haven't noticed, but I am going to go back through my data and see if I can see a trend.

I have a number of days at sea level, Denver, and 9000 ft +.

[C0mbe]

I will discuss this with my doctor and let him know about the article. I doubt that I will be able to go to Frisco for a sleep test, but I might try to arrange for. One in Mexico City, if it would be covered. I will discuss the advantages of the asv in relationship to the article and see if it might be covered.Do any asv's algo function as bipaps or cpaps?
Thanks again

An ASV is a type of bi-level device, and it will also function as a straight CPAP.    To be perfectly honest though, I don't know why anyone would set an ASV machine to anything other than ASvauto (or the PR equivalent), its pretty spectacular at treating both OSA and CSA.