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ResMed Flow Limitation "Index" used in OSCAR
#1
ResMed Flow Limitation "Index" used in OSCAR
Friends,
I am confused, I can not find any explanation of how this "INDEX" is composed?
I am aware there are no “normal” values for it discussed on this Forum. So everyone please  "Help".
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#2
RE: ResMed Flow Limitation "Index" used in OSCAR
The 'Index' is simply the 95th percentile value of all the Flow Limitation values reported every two seconds by the ResMed machines that report it.

There have been discussions of other ways of computing an 'index' but none of them have been implemented in OSCAR.

The Respironics machines report flow limitations differently, and, AFAIK, do not have an 'index'..
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#3
RE: ResMed Flow Limitation "Index" used in OSCAR
Not sure if this is what you are looking for or not...
http://www.apneaboard.com/wiki/index.php...Limitation
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#4
RE: ResMed Flow Limitation "Index" used in OSCAR
Thanks. Seen that, but as you guys know that is a description on how they define breath Flow Limitation and then there is jump up to an “index”.
Multiple literature searches have come up negative on how ResMed developed this so-called Index.
Pholynyk is correct, there is no one definition for how to construct an Index.
The best is one in my estimation uses amplitude (height), duration (horizontal length) and a frequency...in our case this would be the respiration rate.
I actually did this manually (once) using the snore graph provided by OSCAR. I have too many flow limitations to do this manually.

So I ask myself the question: What explanatory variables explain my Flow limitations?
My Outcome Metric is the Fl Index provided by OSCAR. It's a lot of work to transfer this data to a SAS statistical program....I got a gut feeling that this “Index” is incorrect, so I have been hesitating (procrastinating) for some time.
At least all this extra mental work is helping me sleep better.... Yeah, I know   Laugh-a-lot
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#5
RE: ResMed Flow Limitation "Index" used in OSCAR
Here is a patent describing a method of quantifying an index for inspiratory flow limitation. The patent is worded in general terms in order to protect as much of the intellectual property as possible, and only offers a clue as to how Resmed may be calculating the index, or more specifically to adjust auto positive air pressure devices to mitigate flow limitation. In relevant part the patent states: "The shape indices may be based on function(s) that ascertain the likelihood of the presence of M-shaped breathing patterns and/or chair-shaped breathing patterns. The measure of ventilation may be based on analysis of current and prior tidal volumes to detect a less than normal patient ventilation. The duty cycle measure may be a ratio of current and prior measures of inspiratory time to respiratory cycle time to detect an increase in the patient's inspiratory cycle time relative to the respiratory cycle time. A pressure setting based on the flow limitation may then be used to adjust the treatment pressure to ameliorate the patient's detected flow limitation condition."
Source: https://patents.google.com/patent/US20110203588A1/en More clues on the implementation of this patent can probably be chased down by following some of the references. Cross references to Sulllivan and Australian patents show this is likely the property of Resmed, but that is not specifically within the article.
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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.
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#6
RE: ResMed Flow Limitation "Index" used in OSCAR
Lots of "may" bes in there. Then again, intellectual property is their stock in trade.
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#7
RE: ResMed Flow Limitation "Index" used in OSCAR
In spite of the contingent language, this shows a fundamental principle of actually affecting therapy and specifically flow limitation through the use of what is effectively pressure support in CPAP (bilevel therapy). This has never been the basis of the Philips therapy which uses Flex as a means of providing momentary pressure relief for comfort, but which restores the CPAP pressure prior to the onset of inspiration in order to maintain the airway. Resmed uses the Easybreathe flow shaping algorithm to accomplish the pressure transitions, and actively enables a bilevel pressure support for therapy against flow limitation, and in its auto CPAP machines uses flow limitation as the key indicator of obstruction to raise pressure. Philips does not actively measure flow limitation, but does use the peak flow rate and respiratory volume, and especially uses snores and events as the controller of pressure increases. This approach also led them to the characteristic pressure increases and decreases to measure the effect of a 1.5 cm higher pressure about every 20 minutes.
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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.
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