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How much should AHI increase from sea level to 6500 ft altitude?
#1
How much should AHI increase from sea level to 6500 ft altitude?
I am not currently using CPAP because my AHI is consistently less than 5 AHI/hour at my home. I live close to sea level and have a cabin at 6500 ft above sea level.  When I measure my AHI at sea level, it varies from 3-5/hour.  When I go to my cabin at 6500 feet above sea level, my AHI increases to 20-30 AHI/hour.  Since I am not using CPAP, I monitor my AHI with a finger mounted sensor which plugs into a digital pulse oximeter 'watch' which records my oxygen saturation and pulse throughout the night. I then upload the data via bluetooth in the morning and it shows charts of oxygen saturation and pulse rate over time. It also calculates and AHI per hour. Is this increase in AHI at altitude normal? Should I use my CPAP at altitude and not at sea level?  The digital pulse oximeter watch is made by Innovo (model CMF 50F).

I appreciate any guidance on why my AHI changes so much with altitude.  Thanks.
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#2
RE: How much should AHI increase from sea level to 6500 ft altitude?
I( suspect that you should use your ASV at altitude. If you use your DS at altitude I could validate that guess. It would take seeing your nightly charts and possibly a zoomed view of your CA events.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
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#3
RE: How much should AHI increase from sea level to 6500 ft altitude?
Altitude can greatly increase AHI, and particularly central events. For sensitive individuals, altitude results in deeper and more rapid breathing which can decrease your CO2 balance, or more technically, "hypocapnia". To combat this, we have several tools. The easiest is to simply put your CPAP into fixed pressure near your minimum requirement and turn down Flex to the minimum. Another effective method would be to use "enhanced expiratory rebreathing space (EERS)" to increase CO2 to normal levels http://www.apneaboard.com/wiki/index.php...ace_(EERS) Finally, some members with very high central apnea at altitude can use adaptive servo ventilation (ASV) to directly treat central apnea.

One of the easiest ways to deal with this is to take Diamox (Acetazolamide) before traveling to high altitude. This drug helps with many high altitude problem including pulmonary edema, but it also slightly acidifies the blood and makes you less susceptible to central apnea. Talk to your doctor about a prescription for Acetazolamide to be taken as needed for high altitude sickness (headache, blood pressure changes, central apnea) and start taking it a couple days before traveling. Stay hydrated and you will see a noticeable result in your PAP therapy, especially if you set the pressure at 6.0 fixed. This will prevent the OA events and not result in the abundant CA events that are increasing your AHI.

Edit: I see Fred has posted at the same time. I was unaware you have access to ASV. If that is the case, then it is the most appropriate therapy when traveling to high altitude.
Sleeprider
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#4
RE: How much should AHI increase from sea level to 6500 ft altitude?
I greatly appreciate your reply!

I have stopped using the CPAP at sea level since my AHI tends to run less than 5/hour.  Do you believe that my increase in AHI from <5 at sea level to >20/hour when I go to 6500 ft altitude is primarily due to Central apnea events? Is there a way that I can determine if my AHI is being driven by CA or OSA? In addition to taking Diamox, would it also be helpful to make the modifications to my nasal pillow mask?

I have a Philips Respironics DreamStation which does not support ASV (to my knowledge).  I can get some Diamox before my next trip to altitude.  Do you think Diamox alone can eliminate the CA events that I am seeing at altitude?  Many thanks for your thoughtful response!
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#5
RE: How much should AHI increase from sea level to 6500 ft altitude?
(10-11-2020, 03:12 PM)garyrgraham Wrote:   Since I am not using CPAP, I monitor my AHI with a finger mounted sensor which plugs into a digital pulse oximeter 'watch' which records my oxygen saturation and pulse throughout the night. I then upload the data via bluetooth in the morning and it shows charts of oxygen saturation and pulse rate over time. It also calculates and AHI per hour. Is this increase in AHI at altitude normal? Should I use my CPAP at altitude and not at sea level?  The digital pulse oximeter watch is made by Innovo (model CMF 50F).

Can you post a screenshot of the report you are getting?
Using a 13" MacBook Air (2017), MacOS Catalina (10.15.7), OSCAR v1.2.0
In a VM: Win10 1909 (18363.836)

Installing OSCAR on a Mac
Organizing your OSCAR charts
Attaching images and files for the forum
OSCAR Help
OSCAR Data Interpretation
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#6
RE: How much should AHI increase from sea level to 6500 ft altitude?
Gary, you say your AHI is less than 5 at sea-level, but you surely realize that is WITH the CPAP. When you remove that therapy, your AHI returns to what it was in your diagnostic study. You want to believe you're cured, but it simply doesn't work that way.

My reply above assumes that when you go to higher altitude your apnea becomes central or mixed. Since you're not using software, none of us really knows. Why not download the free OSCAR program and then you can know the kinds of events, you have and optimize your therapy? An AHI is not acceptable with CPAP, and it certainly doesn't mean it isn't much higher without CPAP. We can probably help you to better understand your therapy and get events down to less than 2 per hour. As it stands the health you are hurting is your own, and your sleep disordered breathing and obstructive apnea are untreated.
Sleeprider
Apnea Board Moderator
www.ApneaBoard.com

____________________________________________
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#7
RE: How much should AHI increase from sea level to 6500 ft altitude?
My AHI is <5/hour at sea level WITHOUT CPAP. That is why I'm not using the CPAP at sea level. I lost some weight and that may be the reason that my AHI is <5. However, my AHI is 20-30 /hour WITHOUT CPAP when I travel to 6500 ft altitude. Does OSCAR tell me whether my events are OSA or CA? I have tried using my CPAP at altitude, but I wake up gasping for breath several times during the night. Not sure if that is because I'm not used to CPAP or because CA is causing it. Thanks.
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#8
RE: How much should AHI increase from sea level to 6500 ft altitude?
Attached is a copy of the my oxygen saturation and pulse rate at sea level w/o CPAP
.pdf   3.5 AHI at Sea Level without CPAP.pdf (Size: 356.86 KB / Downloads: 6)

Also attaching the same chart at 6500 ft altitude.  Also w/o CPAP.
.pdf   28 AHI at 6500 feet altitude without CPAP.pdf (Size: 389.46 KB / Downloads: 7)

These readings were taken the same week when I travelled from my sea level home to my 6500 ft altitude cabin.  I am trying to use CPAP at the cabin (Philips Dreamstation with Resmed nose pillow), but I find myself waking up gasping for air after a few hours.
Appreciate any interpretation and recommendations!
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#9
RE: How much should AHI increase from sea level to 6500 ft altitude?
I just downloaded the OSCAR software and am trying to read the data from my pulse oximeter directly. I will post using the OSCAR software which is very informative if I'm successful. I want nothing more to resolve my sleep issues and you've been extremely informative explaining the different effects at altitude!  Thank you!
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#10
RE: How much should AHI increase from sea level to 6500 ft altitude?
Those figures are not AHI calculations.  They are an index of SpO2 drops per hour (or SpO2 Drop Index, usually 4% drop for ~10 seconds).  While they may indicate you are having apnea events, there are other conditions that can cause your SpO2 levels drop.   
That index is telling you that your O2 levels dropped >=4% for an average of 28.7 times per hour that night.

You would need to use your CPAP machine in order to get your AHI.
Using a 13" MacBook Air (2017), MacOS Catalina (10.15.7), OSCAR v1.2.0
In a VM: Win10 1909 (18363.836)

Installing OSCAR on a Mac
Organizing your OSCAR charts
Attaching images and files for the forum
OSCAR Help
OSCAR Data Interpretation
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