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[Equipment] Respironics - a newly reported defect
#1
Respironics - a newly reported defect
This post is to let you know about an article a Sleep Medicine physician and I just published in the medical literature (https://www.acpjournals.org/doi/10.7326/aimcc.2022.0145 ) and to thank this community for your role in making this publication possible.

A couple of years ago, I was having a lot of trouble with my Respironics CPAP machine. The pressure would bump up, causing mask leaks and waking me up. Then, one night, I was lying in bed awake with my CPAP on and saw the machine's display increasing the pressure. I wasn't having apnea spells while awake, so this was rather intriguing. Thanks to OSCAR (and thanks to everyone involved in programming OSCAR!) I was able to determine that the machine was incorrectly sensing vibratory snores and bumping up the pressure in response.

It took me a while to convince my medical providers of this, but eventually I got a new machine. If you read the article, you'll see that, once my Sleep Medicine doc knew to look for this problem, he saw it in two other patients. And a member of this community pointed me at several other posts here about the same problem, which we also cited in our article.

Thanks to OSCAR and thanks to those in this community who took the time to post about this. I hope our article leads Respironics to improve their machines, but in the meantime there are work-arounds our Sleep Medicine docs can implement - but only if they know to look for this problem.
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#2
RE: Respironics - a newly reported defect
A very interesting article. Thank you for the mention of OSCAR in a professional journal. I don't expect OSCAR to replace the manufacturers software on clinics, but it's nice to see it's profile raised among doctors and therapists.
Apnea Board Monitors are members who help oversee the smooth functioning of the Board. They are also members of the Advisory Committee which helps shape Apnea Board's rules & policies. Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#3
RE: Respironics - a newly reported defect
Philips has used vibratory snore as a fundamental component in the auto-pressure algorithms in both auto-CPAP and BiPAP algorithms. Resmed on the other hand, uses primarily flow limitation for this purpose. Both are subject to error due to signal interference and individual's response to pending obstruction. Not everyone snores with increasing obstruction, resulting in a failure of Philips machines to increase pressure ahead of events, or detection of snores or interference unrelated to obstruction. Similarly, Resmed is renown for rapidly increasing pressure in response to flow limitation which in many cases appears to prevent obstruction, while in other cases results in higher pressure with no apparent relief of FL.

I don't know that either case is a machine or algorithm defect, as they are long-standing features of automatic pressure adjustment and the subject of numerous patents and considerable research that endeavored to demonstrate their use as effective in preventing obstructive sleep apnea in more individuals than those that did not respond to those pressure control parameters. I think the article presents an interesting conclusion and perspective considering a very small, mainly elderly cohort being considered. I think auto-pressure adjustment has its place in CPAP therapy, and that snores, peak flow rate or flow limitation are the basis of current auto-CPAP algorithms. I'm not sure the fact they don't work for everyone is a defect as opposed to a well-known individual response to positive air pressure therapy, and the alternative of fixed pressure, may also not be universally better. Both Philips and Resmed algorithm patents date back to legacy machines from the 1990s to early 2000s, and are very difficult to change or improve due to the FDA medical device approval process. I'll depart from the findings of your paper to add that the use of bilevel pressure seems to be beneficial to the majority of OSA patients, even when it is limited to the 3-cm range of the Resmed exhale pressure relief (EPR), which Resmed markets as strictly a comfort feature, but clearly has therapy applications.
Sleeprider
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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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#4
RE: Respironics - a newly reported defect
Wonderful post! Thanks for raising this issue.
DaveL
DaveL
compliant for 35 years /// Still learning!

ResMed N20; ResMed P30i modified headgear; F&P Evora Full FFM



I'm just a cpap user like you. I don't give medical advice. Seek the advice of a physician before seeking treatment for medical conditions including sleep apnea. Sleep-well

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#5
YOUR DISCOVERY
Award-worthy discovery, Dr. Bob.  Extremely few people would have the insight, analytical skils, expertise, and persistence to make similar findings; and then to take the necessary actions to benefit an entire community. 

It's upsetting to consider the number of CPAP trial or early users that might have abandoned their CPAP use prematurely as a result of this 'flaw' in some/many/all Philips systems - increasing the statistics of those who were unable to tolerate their CPAP machine and abandoning the technology altogether - while the reality may have been that their CPAP machines may have inappropriately increased pressures unnecessarily, decreasing patient comfort.  There may be many others that continued using their devices, only to have increased discomfort, awakenings, central apneas as a result of higher unnecessary pressures, etc.

This leaves us with more questions:
  • Is it a result of Philips sleep algorithms, or more to do with a system’s analytical and response functions (assuming it's not a defective hardware component)?
  • Which devices have been affected?
  • Will Philips quickly notify potentially affected users, sleep labs, sleep specialists, etc.?
  • Assuming it’s purely a software issue, is this easily fixable with a software update?
  • Will Philips provide the update in a timely manner?
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#6
RE: Respironics - a newly reported defect
I'm with Sleeprider on this one.
We have long understood the differences in the algorithms between Philips and ResMed.
I see the flaw as more in the medical system in assuming ALL APAPs will automatically find the users optimum pressure when given a 4-20 initial setting. This is absolutely not true for either vendor though given these settings ResMed has a much better chance of performing better.

Philips algorithms are known to be slow to the point that they need an initial pressure much closer to where a titration would determine a fixed CPAP pressure to be successful. IMHO this is how the PR algorithms are designed.
The flaw they have is that in the presence of continuous logged obstructive events which should call for continuous pressure increases PR will actually lower the pressure for a period to see if you still need higher pressure. Note this is during a period of continuous spaced obstructive events that should be continuously incrementally be increasing pressure.
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#7
RE: Respironics - a newly reported defect
@Sleeprider, thanks for a very sophisticated commentary on the PR algorithm. I want to point out the distinction between optimal algorithm and accuracy of sensing. In all the cases in our series, the machines when first used did not sense a lot of vibratory snores. The VS rate rose over weeks or months. For me, the VS rate rose, dropped with a new machine, and then rose again, dropping with a third machine. 

Regardless of the potential benefit of including VS in the algorithm, wouldn't you agree that this appears to be a sensing error?

Thanks!
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#8
RE: Respironics - a newly reported defect
Dr. Bob, my opinion is that the Philips Auto PAP algorithms are overly dependent on snore detection to respond to obstruction, and that by the time snores are present or detected in a flow wave, the obstruction is already well-advanced. This is why Philips notoriously fails to get ahead of apnea and serious flow restriction, and let's not forget the auto-PAP algorithm is cancelled when "variable breathing" is detected. See my wiki on that topic here: http://www.apneaboard.com/wiki/index.php..._Breathing

With regard to accuracy of sensing, the Philips samples and records the flow rate at 5x per second compared to Resmed's 25x per second. This lack of resolution means there are a number of nuanced changes that are missed. The emphasis by Resmed in measuring flow limitation means their auto pressure algorithm can respond much faster to changes in peak respiratory flow, rather than wait on aberrations like snores and more significant flow reduction. I'm sure we are more on the same page rather than disagreeing.
Sleeprider
Apnea Board Moderator
www.ApneaBoard.com

____________________________________________
Download OSCAR Software
Soft Cervical Collar
Optimizing Therapy
Organize your OSCAR Charts
Attaching Files
Mask Primer
How To Deal With Equipment Supplier


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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