AHI Meaning

Being new to Sleep Apnea I was wondering if someone can help me understand AHI. When I went for my sleep test the Dr said I had severe Apnea with an index of 61. I recently started using the Resmed s9 unit and each night the index is in the neighborhood of 0.4 to 1.5. Is this an indication that the S9 is working to help me or does it indicate that the original diagnosis was wrong.

Guest wrote:Being new to Sleep Apnea I was wondering if someone can help me understand AHI. When I went for my sleep test the Dr said I had severe Apnea with an index of 61. I recently started using the Resmed s9 unit and each night the index is in the neighborhood of 0.4 to 1.5. Is this an indication that the S9 is working to help me or does it indicate that the original diagnosis was wrong.

Your current AHI of 0.4 to 1.5 is excellent! AHI under 5.0 is generally considered effective treatment, and you're well under that. That's exactly what you want to see, and indicates that therapy is working very well for you!

AHI is the average number of apneas + hypopneas that you have per hour, averaged throughout the night. You're having just a few now, which is perfectly fine. Keep in mind that CPAP is not a permanent cure for sleep apnea. If you stop using the machine, you will have a high AHI again, as you did during your sleep study.

As you probably know, an obstructive apnea is when your airway collapses and you can't breathe. Your body can be starved of oxygen when this happens, which can lead to many other health problems over time, including high blood pressure, heart problems, stroke, and diabetes. Hypopneas are partial airway obstructions. The air blowing from the CPAP machine keeps your airway open, so it won't collapse, therefore preventing most apneas from occurring. It is a very effective form of therapy.

To learn more, check out the "CPAP Wiki" (at the top of the screen) and search past forum posts too. If you have any questions, feel free to ask! We're here to support each other.

Less than 5 means your machine is doing what it is supposed to do.

AHI is the average number of apneas and hypopneas per hour. The sleep lab counted up all of your events and divided that number by the number of hours you slept.

The sleep study determined that you have sleep apnea. The numbers from your machine show that it is helping you. The lower your AHI the better. Most people say that an AHI under 5 is good, but they also try to reduce thier AHI even lower. Your numbers are great.

But there's one catch (isn't there always a catch?): Your leak rate. If it is high, the AHI number from the machine may not be accurate. So let us know what the machine displays for leak.

Leakage rate is 7.2. Not sure if that is good or bad.

Guest wrote:Leakage rate is 7.2. Not sure if that is good or bad.

The leak rate is only meaningful when the mask (make & model) AND pressure are known. Each mask has a chart with it to show the leak for a given pressure. Some can vary with size.

A high leak rate can prevent the machine from detecting some or all events - depending when the leak and the events occurred. That is why the software charts are preferred to the LCD data displays.

When giving the AHI always give the pressure, mask (make & model), and leak rate for the data to have meaning. The machine make and model are also useful in understanding the data.

Guest wrote:Being new to Sleep Apnea I was wondering if someone can help me understand AHI. When I went for my sleep test the Dr said I had severe Apnea with an index of 61. I recently started using the Resmed s9 unit and each night the index is in the neighborhood of 0.4 to 1.5. Is this an indication that the S9 is working to help me or does it indicate that the original diagnosis was wrong.

Guest wrote:Leakage rate is 7.2. Not sure if that is good or bad.

I assume that your leak rate of 7.2 is in L/min. The ResMed machines report the Leak Rate a little different than other machines. There is a "mask setting" on the ResMed machines. When that's set correctly (to correspond with the type of mask you're using), the mask's "flow rate" (the amount of air it expels through the mask vent) is subtracted before the leak rate is reported by the machine. The ideal leak rate with a ResMed machine is zero, but anything under 24 L/min (0.4 L/sec) is acceptable. If the leak rate was higher than that, then the machine couldn't compensate and your therapy would be affected.

Your leak rate appears to be fine, but you may want to watch for a few things. You didn't mention which mask you wear. If it's a nasal or nasal pillows mask, watch for air escaping through your mouth. This may happen while you're deep asleep, when all your muscles are fully relaxed, so you may sleep through that. You may need a chin strap and/or mouth taping to prevent that. Or, you may need to use a full-face mask. And, with any mask, the nasal pillows or cushion can become dislodged and leak during the night.

It looks like you're off to a great start! The numbers are an important guide, but ultimately, it is about how you feel.

Thanks to all for the advice and feedback. I am starting to get a better appreciation for what is involved here.

I am using the RESMED S9 in auto mode
Pressure is set in th 5 to 12 range
The LED reports that average pressure (I guess) is about 10
Mask is Mirage Softgel Nasal Mask


I do have a card reader on my PC but I do not have any software that recognizes the stored file types on the card. I believe they are .edf files. Any advice on reading these files or am I getting into too much detail for someone who is new to all of this?

dwsupt wrote:Less than 5 means your machine is doing what it is supposed to do.

Does using the auto on/off feature of my ResMed S9 machine affect the AHI and leak rate readings?

Guest wrote:Thanks to all for the advice and feedback. I am starting to get a better appreciation for what is involved here.

I am using the RESMED S9 in auto mode
Pressure is set in th 5 to 12 range
The LED reports that average pressure (I guess) is about 10
Mask is Mirage Softgel Nasal Mask


I do have a card reader on my PC but I do not have any software that recognizes the stored file types on the card. I believe they are .edf files. Any advice on reading these files or am I getting into too much detail for someone who is new to all of this?

You can use sleepyhead and ResScan software to read the data as long as your machine is a Resmed S9 autoset and NOT the Auto Escape. Both software programs are free.