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measurement uncertainty
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0rangebear Offline

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Posts: 342
Joined: Jan 2016

Machine: ResMed AirSence 10
Mask Type: Other
Mask Make & Model: Amara View
Humidifier: HumidAire (Built-in)
CPAP Pressure: APAP 12.8-15 EPR 3 (cmH2O)
CPAP Software: ResScan SleepyHead

Other Comments: Ramp off

Sex: Male
Location: Brighton Colorado

Post: #1
measurement uncertainty
Can anyone explain the variation in these reports?

2004-Bon Jovi
it'll take more than a doctor to prescribe a remedy

Observations and recommendations communicated here are the perceptions of the writer and should not be misconstrued as medical advice.
03-07-2016 12:28 PM
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DeepBreathing Offline
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Posts: 2,296
Joined: Sep 2013

Machine: Resmed S9 VPAP Adapt
Mask Type: Full face mask
Mask Make & Model: F&P Simplus
Humidifier: Resmed H5i
CPAP Pressure: EPAP: 9 - 15 PS: 3 - 10
CPAP Software: ResScan SleepyHead

Other Comments:

Sex: Male
Location: Perth, Western Australia

Post: #2
RE: measurement uncertainty
Not sure which particular variation you mean - there are quite a few.

Compliance

ResScan reports the percentage of days with usage > 4 hours. I'm not sure what Sleepyhead reports for compliance.

Indices

ResScan truncates an index to one decimal place before using it in a calculation. Hence there are substantial rounding errors. SleepyHead reports to two decimal places and I suspect it doesn't truncate at all in its calculations. The outcome of this is that the SleepyHead numbers usually add up pretty closely while the ResScan will show cumulative errors over a large number of nights.

I think the fact that Resmed aren't too fussed about these errors is an indication that we shouldn't get too hung up on the exact numbers. They are an important indication of efficacy, but they are no the be all and end all.

DeepBreathing
Apnea Board Moderator
www.ApneaBoard.com


Bed

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
03-08-2016 07:45 AM
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0rangebear Offline

Advisory Members

Posts: 342
Joined: Jan 2016

Machine: ResMed AirSence 10
Mask Type: Other
Mask Make & Model: Amara View
Humidifier: HumidAire (Built-in)
CPAP Pressure: APAP 12.8-15 EPR 3 (cmH2O)
CPAP Software: ResScan SleepyHead

Other Comments: Ramp off

Sex: Male
Location: Brighton Colorado

Post: #3
RE: measurement uncertainty
(03-08-2016 07:45 AM)DeepBreathing Wrote:  Not sure which particular variation you mean - there are quite a few.

Compliance

ResScan reports the percentage of days with usage > 4 hours. I'm not sure what Sleepyhead reports for compliance.

Indices

ResScan truncates an index to one decimal place before using it in a calculation. Hence there are substantial rounding errors. SleepyHead reports to two decimal places and I suspect it doesn't truncate at all in its calculations. The outcome of this is that the SleepyHead numbers usually add up pretty closely while the ResScan will show cumulative errors over a large number of nights.

I think the fact that Resmed aren't too fussed about these errors is an indication that we shouldn't get too hung up on the exact numbers. They are an important indication of efficacy, but they are no the be all and end all.

I have attached some more objective evidence of the measurement accuracy issue maybe there is something I am doing wrong with the software
I timed three night on my cell phone and there is a contestant 2 second deviation in rescan and more in sleepy head that will effect the compliance report.
in addition; on two of the nights the AHI and total time don't agree insight the Sleephead tool. On two different sleepy head tabs Daily and the Statistics screen give different numbers
see attached data from screen shots.

Rounding does explain some of it, but there is larger issue here that rounding

2004-Bon Jovi
it'll take more than a doctor to prescribe a remedy

Observations and recommendations communicated here are the perceptions of the writer and should not be misconstrued as medical advice.
03-08-2016 11:44 PM
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DeepBreathing Offline
Wiki Editor
Moderators

Posts: 2,296
Joined: Sep 2013

Machine: Resmed S9 VPAP Adapt
Mask Type: Full face mask
Mask Make & Model: F&P Simplus
Humidifier: Resmed H5i
CPAP Pressure: EPAP: 9 - 15 PS: 3 - 10
CPAP Software: ResScan SleepyHead

Other Comments:

Sex: Male
Location: Perth, Western Australia

Post: #4
RE: measurement uncertainty
If you look at the ResScan summary graphs you will see there is a "usage" and "total usage" graphs which (on my machine) are typically two minutes different. Don't ask me why.

I'm not seeing any significant discrepancy between SH and RS in terms of the overall usage - they are the same to within a minute. SH does tell you the sleep / wake times and they are consistent with the durations in your charts. ResScan doesn't tell you this information, but you can extract it from the detailed chart. Have a look at what time you went to sleep / woke on the night of 6 March. According to SH you only slept 35 minutes compared with 4:10 hrs on ResScan. What does the flow rate chart look like on SH? Does it extend for 4 hours or 35 minutes?

Another thought - SleepyHead has the ability to ignore short mask sessions or combine several mask sessions into one. Got to Files | Preferences | Import and check that "Combine close sessions" and "Ignore short sessions" are turned off. Also check that the day split time is 12:00pm (ie noon). And check if the mask sessions are the same on both programs. On ResScan it's on the usage chart in the summary chart page.

DeepBreathing
Apnea Board Moderator
www.ApneaBoard.com


Bed

INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
03-09-2016 12:13 AM
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