AHI = 0?
Let's start at the end.
The question is: Why can't an adjustable pressure machine, APAP, yield an AHI of 0?
The question isn't about my AHI, but one on general. Please don't ask for charts from OSCAR as they are moot, that is, have little to no relevance. This is a theoretical question, though I'll use myself is real data. Please don't take offense at that previous sentence. I'm not asking for a diagnosis of a problem.
Main Premises:
1. Using an APAP, both lower and upper pressures are not reached on a year's data from OSCAR. In other words, using my settings as an example (only as an example), the readings have never gone below 14.4 ( it can't!) nor have they hit 17 and remained there. If readings locked on 17 for a period, the pressure would need to be raised.
2. AHI stands for, Apnea-Hypopnea Index. An AHI less than 5 is considered "normal."
3. Hypopnea is defined as "The technical definition of a hypopnea is 10 seconds or more of shallow breathing in which a person’s airflow drops by at least 30%." https://www.sleepfoundation.org/sleep-apnea/hypopnea 08/29/2022
4. Apnea is defined as "...your airways are fully obstructed so that you do stop breathing for 10 seconds or more during the night." https://www.webmd.com/sleep-disorders/sl...a-overview 8/29/2022
5. Both hypopnea and apnea are treatable with a CPAP, or APAP.
Discussion:
Therefore to be included in the calculation of the AHI, both conditions must last 10 seconds while Premise No. 1 is true. Ten seconds, the upper pressure is never reached. Ten seconds is a long time, folks.
The machine has ten seconds to resolve that hypopnea/apnea (hereinafter, "event"). According to a sleep technician at a DME supplier, the machine may send out a series of pulses to determine if the event is central or obstructive. I have felt that happen, and it only takes up one or two seconds. Just to be generous, let's say that leaves seven (7) seconds.
New question that just popped up. Is the machine designed to resolve the event only AFTER the 10 seconds or is it designed to resolve it DURING the 10 seconds?
If the event goes beyond the 10 seconds it becomes part of the AHI. That brings us back to the ~7 seconds remaining to resolve the event.
However, if the AHI is greater than zero (0), then the machine has failed to resolve the event. Now again, we are taking Premise No. 1 as true, that is, the upper setting is never bumped in one year of data (on my machine).
So why isn't the AHI 0? Certainly the machine can raise the pressure from 14.4 to 17 (my settings) in seven seconds? I do not use a ramp up upon starting the machine, and in seven seconds it can go from 0 to 8. Yet, the pressure has never gone as high as 17 in one year of data, and the AHI is greater than zero!
It seems to me that the algorithm, software, is not designed to get an AHI of 0. If the brakes on a car is to bring the car to a complete stop, that is, 0 mph, then if it fails at that, it is considered a fault, an error, a mistake. Or, in the case of a CPAP, is it by design. Is the AHI really accurate? Or ("conspiracy theory" coming) is it to produce higher AHIs to sell more machines?
This brings us back to the original question: Why can't an adjustable pressure machine, APAP, yield an AHI of 0?
Lawrence
The question is: Why can't an adjustable pressure machine, APAP, yield an AHI of 0?
The question isn't about my AHI, but one on general. Please don't ask for charts from OSCAR as they are moot, that is, have little to no relevance. This is a theoretical question, though I'll use myself is real data. Please don't take offense at that previous sentence. I'm not asking for a diagnosis of a problem.
Main Premises:
1. Using an APAP, both lower and upper pressures are not reached on a year's data from OSCAR. In other words, using my settings as an example (only as an example), the readings have never gone below 14.4 ( it can't!) nor have they hit 17 and remained there. If readings locked on 17 for a period, the pressure would need to be raised.
2. AHI stands for, Apnea-Hypopnea Index. An AHI less than 5 is considered "normal."
3. Hypopnea is defined as "The technical definition of a hypopnea is 10 seconds or more of shallow breathing in which a person’s airflow drops by at least 30%." https://www.sleepfoundation.org/sleep-apnea/hypopnea 08/29/2022
4. Apnea is defined as "...your airways are fully obstructed so that you do stop breathing for 10 seconds or more during the night." https://www.webmd.com/sleep-disorders/sl...a-overview 8/29/2022
5. Both hypopnea and apnea are treatable with a CPAP, or APAP.
Discussion:
Therefore to be included in the calculation of the AHI, both conditions must last 10 seconds while Premise No. 1 is true. Ten seconds, the upper pressure is never reached. Ten seconds is a long time, folks.
The machine has ten seconds to resolve that hypopnea/apnea (hereinafter, "event"). According to a sleep technician at a DME supplier, the machine may send out a series of pulses to determine if the event is central or obstructive. I have felt that happen, and it only takes up one or two seconds. Just to be generous, let's say that leaves seven (7) seconds.
New question that just popped up. Is the machine designed to resolve the event only AFTER the 10 seconds or is it designed to resolve it DURING the 10 seconds?
If the event goes beyond the 10 seconds it becomes part of the AHI. That brings us back to the ~7 seconds remaining to resolve the event.
However, if the AHI is greater than zero (0), then the machine has failed to resolve the event. Now again, we are taking Premise No. 1 as true, that is, the upper setting is never bumped in one year of data (on my machine).
So why isn't the AHI 0? Certainly the machine can raise the pressure from 14.4 to 17 (my settings) in seven seconds? I do not use a ramp up upon starting the machine, and in seven seconds it can go from 0 to 8. Yet, the pressure has never gone as high as 17 in one year of data, and the AHI is greater than zero!
It seems to me that the algorithm, software, is not designed to get an AHI of 0. If the brakes on a car is to bring the car to a complete stop, that is, 0 mph, then if it fails at that, it is considered a fault, an error, a mistake. Or, in the case of a CPAP, is it by design. Is the AHI really accurate? Or ("conspiracy theory" coming) is it to produce higher AHIs to sell more machines?
This brings us back to the original question: Why can't an adjustable pressure machine, APAP, yield an AHI of 0?
Lawrence
