Resmed S9 AHI

[HerdingDogRescuer]

I am curious to know how the S9 calculates the AHI. One would think that you would need a effort wave form to accurately differentiate apneas and hypopneas. I gather it is all based on airflow and resistance.

Last few nights my AHI has dropped to 1.1, but my pressure is up to 9.4. When I first started a month ago or so the AHI was in the 2-3 range and my pressure was 8.4-8.8.

[idamtnboy]

I am curious to know how the S9 calculates the AHI. One would think that you would need a effort wave form to accurately differentiate apneas and hypopneas. I gather it is all based on airflow and resistance.

Last few nights my AHI has dropped to 1.1, but my pressure is up to 9.4. When I first started a month ago or so the AHI was in the 2-3 range and my pressure was 8.4-8.8.

Which S9 do you have? Hopefully it's an Autoset or Elite so you will have data to look at. Assuming that, install Resscan or Sleepyhead and look at the events graph and flow graph. Study the flow graph characteristic for each event. That'll give you a good visual description of of OA, CA, and hypopnea.

The actual algorithms the various machines use are proprietary and probably extremely complicated for some of the machines.