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00:59 AHI = 40.0; at 01:00 AHI = 1.0
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jcarerra Offline

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Post: #1
00:59 AHI = 40.0; at 01:00 AHI = 1.0
If I wake at 0059, my AHI is 40.
If I wake at 0001, my AHI is 1.

I conclude that AHI is useless.

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(This post was last modified: 07-06-2014 04:27 PM by jcarerra.)
07-06-2014 04:23 PM
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diamaunt Offline

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Post: #2
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
well, you're certainly welcome to your opinion.
07-06-2014 04:35 PM
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jcarerra Offline

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Post: #3
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
If one minute in wake time changes your AHI from 40 to 1, can you explain how that is useful?

Imagine I am a person (99% of users) who simply look at the display. One minute difference in wake time gives you a COMPLETELY different conclusion about your status. How can I ever trust the AHI number?

I take it from your reply that you disagree with my conclusion. I am fully open to learning why that conclusion (my opinion) is wrong--given the facts in this REAL WORLD example,
07-06-2014 04:49 PM
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zonk Offline

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Post: #4
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:23 PM)jcarerra Wrote:  If I wake at 0059, my AHI is 40.
If I wake at 0001, my AHI is 1.

I conclude that AHI is useless.
It does not add up, too many events, something is not right
First of all, see your sleep doc, something might need some adjustment

Is the clock set correctly, so new day start at 12 noon, not at 12 midnight
If not applicable, try rebooting
07-06-2014 04:56 PM
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Sleepster Offline
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Post: #5
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:23 PM)jcarerra Wrote:  If I wake at 0059, my AHI is 40.
If I wake at 0001, my AHI is 1.

I conclude that AHI is useless.

You are confusing AHI per hour with AHI. (And the way ResScan labels the axis on this graph the confusion is understandable.)

At 0059 if you had continued to have events (apneas and hypopneas) at the rate you were having them, you'd have 40 in the next hour.

At 0001 if you had continued to have events at the rate you were having them, you'd have 1 in the next hour.

In SleepyHead this distinction is clearer because the graph axis is labeled as AHI/hour, rather than AHI.

Here's an analogy. If you are driving at a speed of 60 mi/h at 0059 this indicates that you'll travel 60 mi in the next hour, or one mile in the next minute, or two miles in the next two minutes. But two minutes later, at 0001 you look at your speedometer and it reads only 6 mi/h, indicating that it'll take 10 minutes for you to travel the next mile. So if your destination is 10 miles ahead you might be confused about how long it'll take you to reach it. Two minutes ago you had information that indicated you'd get there in 10 minutes, but now you've got information that indicates it'll take 100 minutes.

You might conclude that speedometer readings are useless, but they're not if you have enough experience to understand how to interpret them.

Sleepster
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07-06-2014 05:05 PM
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diamaunt Offline

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Post: #6
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:49 PM)jcarerra Wrote:  I take it from your reply that you disagree with my conclusion. I am fully open to learning why that conclusion (my opinion) is wrong--given the facts in this REAL WORLD example,

if you're attempting to communicate the feeling that the AHI *stripchart* is useless, then sure, I'd agree with you, I turn it off in sleepyhead.

AHI, which is the *average* number of a's and h's you had over the period of sleep, is not useless, it's an indication how well the machine is doing with your problem.
07-06-2014 05:12 PM
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jcarerra Offline

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Post: #7
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:56 PM)zonk Wrote:  It does not add up, too many events, something is not right
First of all, see your sleep doc, something might need some adjustment

Is the clock set correctly, so new day start at 12 noon, not at 12 midnight
If not applicable, try rebooting

The events are somewhat within my pattern. I have nights of two clusters, one cluster, zero clusters--approximately 1/3 of nights each, roughly. That cluster beginning about 2330 is longer and earlier than I usually see. Clock is set correctly.

But this is aside of the discussion about the usefulness of AHI measure is a one minute time difference can change it from 40 down to 1 (see the AHI line in the chart).

Is it a point here that my data as shown is incorrect?
(I don't mean is "awful," but 'that it cannot be that way period.')
07-06-2014 05:20 PM
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vsheline Offline

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Post: #8
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:23 PM)jcarerra Wrote:  If I wake at 0059, my AHI is 40.
If I wake at 0001, my AHI is 1.

I conclude that AHI is useless.

The hourly AHI is a running accumulation of the total number of As and Hs since the beginning of the hour. The hourly total gets reset to zero at the beginning of each hour.

In ResScan, only if we have no additional As or Hs until the end of the hour, would the number shown be the AHI for the most recently-completed hour.

I, too, keep it un-selected for display (in ResScan), so it will not waste screen space.

Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment. The Advisory Member group provides advice and suggestions to Apnea Board administrators and staff on matters concerning Apnea Board operation and administrative policies - not on matters concerning treatment for Sleep Apnea. I think it is now too late to change the name of the group but I think Voting Member group would perhaps have been a more descriptive name for the group.
(This post was last modified: 07-07-2014 12:41 PM by vsheline.)
07-06-2014 05:31 PM
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diamaunt Offline

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Post: #9
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
(07-06-2014 04:23 PM)jcarerra Wrote:  If I wake at 0059, my AHI is 40.
If I wake at 0001, my AHI is 1.

I conclude that AHI is useless.

you'll also notice, perhaps, that the chart you listed does not say "AHI" period, it says "AHI EVENTS PER HOUR", ergo, it resets every hour.

so, your conclusion is baseless.
07-06-2014 05:35 PM
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zonk Offline

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Post: #10
RE: 00:59 AHI = 40.0; at 01:00 AHI = 1.0
Sleepster hit the nail on the head
From http://www.resmed.com/au/assets/document...ow_eng.pdf

AHI — Apnea–Hypopnea Index
The total number of events is calculated by adding the number of apnea and hypopnea events.
For graphs, the AHI count is incremented at the occurrence of every event and reset every hour

Edit: Also vsheline and diamaunt hit the nail on the head too while I was posting, must be the same hammer Too-funny
(This post was last modified: 07-06-2014 05:49 PM by zonk.)
07-06-2014 05:41 PM
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