Hello Guest, Welcome to Apnea Board !
As a guest, you are limited to certain areas of the board and there are some features you can't use.
To post a message, you must create a free account using a valid email address.

or Create an Account


New Posts   Today's Posts

Can someone explain exactly what flow limitation is?
#1
Can someone explain exactly what flow limitation is?
And what I should be looking for in sleepyhead? 

Thanks
Post Reply Post Reply






Donate to Apnea Board  
#2
RE: Can someone explain exactly what flow limitation is?
Flow Limitation is a breath where the flow is reduced, but not as much as an Apnea (80-100%), or a Hypopnea (50-80%).

http://www.apneaboard.com/wiki/index.php...limitation
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
OSCAR

Download OSCAR
New to Apnea? Helpful tips to ensure success
Soft Cervical Collar
Mask Primer
Dealing with a DME
Organize Charts
Attaching Charts

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.
Post Reply Post Reply
#3
RE: Can someone explain exactly what flow limitation is?
(08-20-2019, 12:49 PM)bonjour Wrote: Flow Limitation is a breath where the flow is reduced, but not as much as an Apnea (80-100%), or a Hypopnea (50-80%).

http://www.apneaboard.com/wiki/index.php...limitation

I was reading on one post where they were saying that the flow limitation was flat on top, so showed mouth breathing. How does that relate? Just not sure what I should be looking for in my results. And how flow limitation had to do with pressure as well........ I'm confused.  I was thinking that was the definition of a RERA, not flow limitation?
Post Reply Post Reply
#4
RE: Can someone explain exactly what flow limitation is?
Definition of a RERA is a series of Flow Limitations that end in arousal. so the two are definitely related.
Though Flow Limitations may be obstructive, that is not a requirement.  And to my knowledge, they have nothing to do with mouth breathing since they may be of any cause and are defined simply as a reduction in flow.  The waveform typically has either a flat and/or sloped top but may also not have these features and simply be a smaller breath.  Sometimes the waveform is referred to as flattened.

The easiest way to look at flow limitations is to look at the Flow Limitation chart which I understand to be a flattening index (0 to 1).  Sometimes Flow limitations are so consistent that they are not recognized because they look very nearly like normal breaths.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
OSCAR

Download OSCAR
New to Apnea? Helpful tips to ensure success
Soft Cervical Collar
Mask Primer
Dealing with a DME
Organize Charts
Attaching Charts

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.
Post Reply Post Reply






Donate to Apnea Board  
#5
RE: Can someone explain exactly what flow limitation is?
(08-20-2019, 01:13 PM)theres126 Wrote:
(08-20-2019, 12:49 PM)bonjour Wrote: Flow Limitation is a breath where the flow is reduced, but not as much as an Apnea (80-100%), or a Hypopnea (50-80%).

http://www.apneaboard.com/wiki/index.php...limitation

I was reading on one post where they were saying that the flow limitation was flat on top, so showed mouth breathing. How does that relate? Just not sure what I should be looking for in my results. And how flow limitation had to do with pressure as well........ I'm confused.  I was thinking that was the definition of a RERA, not flow limitation?

The graph showing the mouth breathing is the leak rate graph while the one showing flow limitations (and therefore  the RERA) is the flow rate graph.
Post Reply Post Reply
#6
RE: Can someone explain exactly what flow limitation is?
to try to restate some of what's been said already: flagged and unflagged flow limitation may appear flat, jagged and/or downward sloped at the top of the 'curve' of inspiration in the flow rate graph. sometimes it may show less amplitude than other breaths, appearing lower above the 0 inspiration/expiration line than non flow limited breaths, with or without the top-of-curve distortions.

in the flow rate graph, mouth leaks can show up as a reduced amplitude inspiration curve and with a non-ffm there may be less to no amplitude (in comparison to inspiration) visible below the 0 inspiration/expiration line. I'm not sure about the ffm but suspect the latter is not characteristic of mouth breathing using a ffm.

I can see how the reduced amplitude inspiration curve might suggest a leak but not necessarily a mouth leak. I don't think the flat top inspiration curve (indicative of flow limitation) has any relationship to mouth leaks.
Post Reply Post Reply
#7
RE: Can someone explain exactly what flow limitation is?
(08-20-2019, 12:33 PM)theres126 Wrote: And what I should be looking for in sleepyhead? 

Thanks

There are different issues in play. Flow limitations are defined by the CPAP makers as part of their auto adjusting pressure. The flow limitation flags you see in Sleepyhead/OSCAR are flagged by the machine using the makers algorithm and displayed by Sleepyhead/OSCAR. Sleepyhead does not do it's own flagging of flow limitations.

So, the flow limitation flags will vary based on the math used by your CPAP company, and can vary from model to model.

Quote:ResMed also determines flow limitation. S8 AutoSet defines flow limitation using flatness of an inspiratory breath. The flatness index is calculated by the RMS deviation from unit scaled flow calculated over the middle 50% of a normalized inspiratory breath.4 From the S9 onward, flow limitation is calculated using a combination of flatness index, breath shape index, ventilation change, and breath duty cycle. Ventilation change is the ratio of the current breath ventilation to recent 3-minute ventilation. Breath duty cycle is the ratio of current breath time of inspiration to total breath time of recent 5 minutes. If a breath is severely flow limited, the flow limitation index will be closer to one and when the breath is normal or round, the flow limitation index will be zero.8

-Treatment of sleep-disordered breathing with positive airway pressure devices: technology update, Karin Gardner Johnson, Douglas Clark Johnson, Medical Devices, 2015

You can find this paper online.
Post Reply Post Reply






Donate to Apnea Board  


Possibly Related Threads...
Thread Author Replies Views Last Post
  New Cpap user - Have messed up flow rate chooie 3 110 Yesterday, 09:46 AM
Last Post: chooie
  Flow Chart pattern- Snoring? Bobaloo 20 424 09-27-2020, 06:41 PM
Last Post: sheepless
  Flow limit question renoir 2 192 09-27-2020, 08:33 AM
Last Post: renoir
  Flat Topped Flow; Help With Chart Please suzdream 27 691 09-24-2020, 04:55 PM
Last Post: Sleeprider
  How does my air flow, etc look to you? airoutlaw 0 109 09-22-2020, 07:23 PM
Last Post: airoutlaw
  Odd problem with air flow with Dreamstations racprops 0 154 09-15-2020, 11:00 AM
Last Post: racprops
  Help to optimize Flow Rate SevereApnea 3 250 09-14-2020, 05:06 AM
Last Post: multicast


New Posts   Today's Posts






About Apnea Board

Apnea Board is an educational web site designed to empower Sleep Apnea patients.