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wiredgeorge
+0 points
·
over 6 years
ago
Sleep
Enthusiast
You breathe in and out. The CPAP machine supplies positive air pressure to keep your airway open. If for some reason you stock breathing for a bit, the machine senses this and counts it as an apnea event (AHI). An obstructive apnea, which the CPAP is designed to mitigate, is when the airway closes down. Your airway is NOT CLEAR but is obstructed during an apnea event. The central apnea is when you just quit breathing for a bit. The machine notes both types and both are counted in the AHI reporting. An AHI less than 5 means you quit breathing less than 5 times per hour regardless of the reason and the range from 0-5 is considered normal and sleep apnea is being treated successfully. Hope this clears things up. If not, ask away! Good luck.
BrainsNeedSleep
+0 points
·
over 6 years
ago
Sleep
Commentator
About that "AHI of 5 is normal", one of my own hot-button issues: I cannot now find it but there was an article a few years ago by a researcher showing that AHIs of over 1.0 were related to higher rates of cardiac issues. I personally reject the idea that "5" an hour is "normal -- that's 35-40 times a night that our sleep is disrupted to one degree or another, and when my AHI was 5 and my sleep doc said I just wasn't giving it enough time (it had been years), I called BS after a year or more of telling him I could NOT FUNCTION. I finally found a specialist who correctly diagnosed my kind of apnea, put me on a particular treatment, and my running 30-day AHI hasn't been over 1.0 in many many months. I've even had a couple of nights with 0.0, which I find hard to believe, and my average usually is around 0.6-7. And I CAN function. If it goes much over 1.0 for several days in a row and I have been awakened several times in the night (sore shoulders, tossing from discomfort), then I really feel it in terms of function.
There are researchers working on better ways to measure and describe how well our sleep is going and how the machine is measuring it, but they haven't gotten anything better out there yet. I wish they would hurry the heck up.
I think the use of the number PER HOUR is somewhat misleading - "only 5" sounds a lot better than "35 to 40" for a 7-8 hour night. So I suggest doing everything possible to get your numbers as low as possible if the number accurately reflects your sleep interruptions. If you have other things interrupting your sleep besides apneas, like a restless partner, or noise on the street, or ambulances going by, that sort of thing, or a cat or dog on the bed, do what you can to minimize those as well.
The machines and oral appliances can only do so much :-)
sleeptech
+0 points
·
over 6 years
ago
Sleep
Enthusiast
The number of 5 was chosen partly because many years ago, before there was much research to go by, someone thought it sounded good. There is more than that. The likelihood of measurable, negative outcomes is very low at an AHI of 5 or below, so it's also based upon raw statistics. However, there's a lot of variation in the way individuals respond. Some people may have a low AHI because their events are isolated to their REM sleep, and those few events can be very severe. In other cases and AHI 5 is enough to make some one highly symptomatic (e.g. very tired). Really, AHI is a useful measurement but, like anything, it is only a guide and needs to be considered in light of other factors. I always think an AHI of 5 sounds pretty bad still.
There is further wrinkle in that an AHI reported by a CPAP machine is not necessarily the same as an AHI reported by a sleep study. Your CPAP machine con only estimate AHI based upon changes in air pressure (i.e. changes in your breathing). Sometimes these will be due to genuine apnoeas or hypopnoeas, but sometimes they will be something else that would be ruled out in a full sleep study. For this reason the AHI reported by your CPAP machine should always be considered a likely overestimation. It is also common for some medical devices to err on the side of a false positive rather than a false negative. This is because it is usually better to be alerted to a possible problem and, upon further investigation, find that it is not real, rather than for a real problem to be missed.
sleeptech
+0 points
·
over 6 years
ago
Sleep
Enthusiast
Certain machines and software refer to central apnoeas as "clear airway" apnoeas. It just means that your breathing is irregular but your airway is open (rather than obstructed). AHI is then a sum of your central or clear airway apnoeas, obstructive apnoeas and hypopnoeas. Your machine is saying that it is picking up some irregularity in your breathing but that your airway is not collapsing. If your AHI is the same as your clear airway number that means that nothing else is happening. Don't worry, that level is within normal range.
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