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+--- Thread: IAH graph drops to zero (/Thread-IAH-graph-drops-to-zero)
IAH graph drops to zero - Eroles3353 - 12-11-2021
Hi, I've been using a Resmed Airsense 10 autoset for years. I regularly view the data with OSCAR, and have been reassured by the relatively good results I see. Lately, I am getting up more often to urinate during the night, and when viewing the IAH data, I've had a worrying surprise, I noticed that when I remove the mask and the air flow stops (Smart Start ON), the IAH graph drops to zero, and when the flow is restored, the graph starts from 0, instead of the IAH that was at the time of stopping. Analyzing the graphs of the different nights, I guess that the IAHI results I get are only for the time since the last stop (when I get up to urinate), so the real IAHI could be much higher than what is recorded in the statistics. Is this so? Or am I interpreting it wrong and the IAH corresponds to the whole night? Is there any way to act, or configuration, so that the IAHI is calculated for the whole night? I attach an example graph, every day something similar happens. I guess it is a behavior of the Airsense 10 machine, not of OSCAR, nor of ResScan.
Thanks in advance for any answer!!!
Jorge
RE: IAH graph drops to zero - Sleeprider - 12-11-2021
The IAH or AHI graph is a moving average of the apnea index per hour. When a session stops, the moving average resets to zero. This graph can show the distribution of events through the night, but as someone that frequently reads and interprets Oscar graphs, I don't find this graphic very useful. Your IAH on this night was 1-event per two hours. That is excellent therapy. The most useful graphs in assessing therapy are Events, Flow Rate, Pressure, Flow Limitation and Leaks.
RE: IAH graph drops to zero - Eroles3353 - 12-11-2021
Thanks! Actually what worries me is not the graph, what worries me is if the final IAH number corresponds only to the last session or sums up all the sessions of the night. The IAH is an index I use to try to know at a glance the evolution of the therapy, especially when I make changes in machine settings, weight, etc.
If the IAH only corresponds to the last session, I cannot use it because the last session of my nights is usually very short.
Thanks a lot!
Jorge
RE: IAH graph drops to zero - Sleeprider - 12-11-2021
Your AIH (apnea+hypopnea per hour) total was 0.68. You had a total of 4 events in 5.85 hours. (4/5.85) = 0.68. Oscar appears to be properly calculating the apnea index.
RE: IAH graph drops to zero - Gideon - 12-11-2021
I never look at this chart unless someone asks a question about it or I testing that chart. It is just not that important.
We get the info you are looking for by looking at the overall AHI and the events chart, looking to see if events are occuring in clusters.
RE: IAH graph drops to zero - Eroles3353 - 12-11-2021
Ok, now I understand! I assumed that IAH calculation was much more complex, considering the severity of the events... I've tested calculation with other days, and that calculation is correct for the whole night. So it's OK for me, it was a false alarm.
Thanks a lot Sleepreader and Gideon for your answers. And also to all of you who contribute to OSCAR, I think it's really very good, much better than the CPAP manufacturer's own...