monica4patience wrote:My AHI had averaged 1.5 for 11 days. Wednesday night it increased to 3.4 and last night was 4.1. I have done nothing differently the past two nights. What would cause the AHI to increase so much?
Are these changes in the 7 day AHI averages on the PR System One's on-board LCD?
Or are they changes in the overnight numbers as seen in Encore Viewer?
It makes a HUGE difference whether this is a ONE day jump in the 7 day AHI on the PR System One's on-board LCD or just the overnight number in Encore Viewer...Because if your 7 day average suddenly jumped from 1.5 to 3.4 overnight, that requires a huge overnight increase in AHI on Wednesday night. (Smaller, steadier increases should have started increasing the AHI from 1.5 before Wednesday night). To see why, we can analyze a very simplified example. For our simplified example, let's suppose you sleep 8 hours every single night with the PR S1 running. And you've had and AHI of 1.5 for at least 11 days. So we'll make a rough and simplified estimate that your actual AHI for the seven nights prior to the Wednesday in question are:
Previous Wednesday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Thursday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Friday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Saturday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Sunday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Monday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Tuesday: AHI = 1.5 (so you had a total of 1.5 * 8 = 12 events that night)
Tuesday Morning 7 day AHI is computed as (84 events)/(56 therapy hours) = 1.5
Now for the Wednesday 7 day AHI, the previous Wednesday's events and therapy hours are dropped out of the calculations and replaced by the current Wedneday night's numbers. We'll continue to assume that you slept for 8 hours with the machine running just to simplify how the numbers in our example calculation work. And I'll let
n be the number of events you had that Wednesday night. Now what we know is this:
The number of events in the AHI calculation is 6*12 + n because you had 12 events on each the six nights Thursday through Tuesday and n events on Wednesday night.
The number of therapy hours is 7*8 = 56 because we're assuming that you slept 8 hours each night in order to simplify things.The seven night AHI average is 3.4 as stated in your post.So now we get the following equation and we have to solve for
n:
(6*12 + n)/56 = 3.472 + n = 190.4 (multiply both sides by 56)
n = 118.4 (subtract 72 from both sides)
So
n is most likely 118 or 119 because you can't have 4/10 of an apnea or a hypopnea. (Remember that
n is the actual
number of apneas and hypopneas you had on Wednesday night.) And that means that your Wednesday night AHI is a whopping huge 118/8 = 14.75 or so.
Note: This is
why I personally think the 7 day average AHI numbers on the System One figures are so useless. I really wish that the System One machines would really provide the overnight numbers on board the way the ResMed S9's do. Just my two cents.