Impact of flow limits?

[CTcentrals]

I've read somewhere that flow limits aren't problematic unless they reach level 1 on scale of 0-1.  I've read here a few times where folks have suggested someone has a problem with flow limits when they are fairly constant but hover mostly around the .5 level with some spikes.

Is there recognized number of flow limits, degree 0-1, or combination when they become problematic?

[Walla Walla]

See Link on "Flow limitation can you explain?".   Should be on this page.

[Sleeprider]

Flow limitations are important to the extent that they indicate an increasing obstruction or resistance to airflow as the inhale progresses. The auto CPAP and bilevel machines are programmed to detect FL and respond to it with increased pressure or pressure support to support respiratory volume and prevent OA which often accompanies FL. I tend to think of FL above 0.4 as something to pay attention to on Resmed data, and Respironics data simply scores an event. The appearance of flow limitation can arise from different causes, and in some individuals it is present on nearly every breath, while for others it is occasional. In CPAP therapy, FL is a significant problem if it increases machine pressure without any benefit to the individual in terms of improved respiration or event rate, or if it causes enough volume reduction that it translates into hypopnea or apnea. Flow limitation is a lot easier to resolve with bilevel than CPAP.

[Sleepster]

Is there recognized number of flow limits, degree 0-1, or combination when they become problematic?

No. You need to look at a bigger picture to investigate problems, whether they involve flow limitation or not.

Flow limitation (measured using a zero to 1 scale) on a CPAP machine is used by the algorithm that auto-adjusts pressure as a signal that the pressure needs to be increased to prevent a pending obstructive apnea or hypopnea. It's characterized by changes in shape of the inspiratory portion (that is the positive parts) of the flow rate graph.

Flow limitation is also discussed in the medical literature as a form of sleep disordered breathing. It can interfere with your sleep in much the same way as hyponeas and apneas. I don't know if this is the same thing that CPAP manufacturers call flow limitation and measure on that zero to 1 scale.

Can you tell us what's going on with you that's prompted you to ask this question?

[CTcentrals]

Got it, thanks.

ct

[CTcentrals]

Sorry about that - I apparently couldn't edit my post.

WallaWalla: Found the flow limitation explanation post.  Thanks.

Sleeprider:  I tend to have quite a few throughout the night and I'd guess half are over .4 without actually counting.  Probably run between 6-11 1's a night. Some nights are remarkable with only a couple, but those are few and far between. The pressure does increase to address most, although I can't tell if the increases improve respiration rate. They do seem to reduce flagged events.  Breathing patterns can look pretty ragged to me.

Sleepster: I've been curious about disordered breathing (my own made up term when I looked at breathing patterns), without knowing the real definition, and without knowing enough about what typical pattern variability can be.  I haven't got to the point of doing any real research at this point, just starting searching and reading. I started getting interested when I got a resmed aircurve 10 ASV in mid-june to replace my dead respironics bipap auto sv and started using SH. While pressure increases to address FL seemed to reduce flagged events, there seemed to be a correlation between FL and unflagged events 50% decrease => 7 seconds, many of which clustered together.  My AHI numbers have been great, yet I don't feel near what I would call refreshed in the morning and I usually somewhat tired throughout the day.  Mind you, I'm not falling asleep at the wheel at 1000 or dozing at work at 1300 like I was the week without a machine, but I think I should feel more energized than I do. The DME who provided the machine set up the min EPAP as 4 and should have been 5 and I hadn't noticed.  I increased min EPAP to 5 a few days ago and have been more refreshed, almost all events gone (0.0, 0.0, .12), unflagged events down to about 6 from 21-33, but still not feeling where I think I should be. Three things I wanted to get sorted out were possible shallow breathing, strange looking flow rate patterns, and flow limits.

Thanks,

ct