Tech questions

[Glen e]

For the experts here, in 20 words or less:

1. How does a Resmed machine calculate the AHI? Is it because it tracks how much you’re breathing in and out and if it dos’nt see a breath,  they report that that’s incident of apnea? What is the technique used?

2. Why do I have a much higher AHI ohappening if I’m not really sleeping but just lying down for 15 minutes, I.e. my minds too busy to sleep, and I get up? I believe you call it “sleep/wake/junk”, what is happening inside the machine,  calculation wise that it does this?

Thank you for your help.

[Sleepster]

1. How does a Resmed machine calculate the AHI? Is it because it tracks how much you’re breathing in and out and if it dos’nt see a breath,  they report that that’s incident of apnea? What is the technique used?

The machine has a flow rate meter. It measures how fast and in which direction you're breathing. If you stop breathing for 10 seconds the machine scores an apnea. It also scores hypopneas when the flow rate drops below some percentage of your usual flow rate. It adds the apneas and the hypopneas together and then divides by the number of hours spent using the machine to get the AHI.

2. Why do I have a much higher AHI ohappening if I’m not really sleeping but just lying down for 15 minutes, I.e. my minds too busy to sleep, and I get up? I believe you call it “sleep/wake/junk”, what is happening inside the machine,  calculation wise that it does this?

You need to look at what type of apnea is scored. An obstructive apnea happens when your airway is blocked. A central apnea (also called a clear airway apnea) happens when your brain doesn't tell your diaphragm to breathe. This can happen when you're awake and concentrating on something. Since it happens when you're awake, it's not sleep disordered breathing and is therefore sometimes called "junk".

The machine uses pressure pulses to distinguish between obstructive apneas (OA) and central apneas (CA).

[Crimson Nape]

AHI is a combination of all your apneas (both CAs and OAs) plus hypopneas. It is used as the dividend on your total sleep session time. Example: You slept for 10 hours (divisor) and had, 1-CA, 3-OA, and 5-hypopneas. The AHI would be calculated as, 8/10 = .8. Likewise, you had 2 events while you napped for 15 minutes (.25 hour) the calculation would be 2/.25 = AHI of 8

Breathing is very irregular while awake, as opposed to a more rhythmic pattern while asleep. A minimum of 10 seconds of a breathing disruption will qualify as an event. It is very common at the onset of sleep and while you are in the awaking phase to have an erratic breathing pattern, thus registering an event. This is known a "Sleep-Wake-Junk" (SWJ).

I hope I've answered your questions.

[Glen e]

Thank you....