Flow Limitation

[jerryfudd]

Hi all, still trying to get my head around flow limitation! Is it good that over time this has gone down?

[khauser]

Think of a flow limitation as an almost apnea. It means the machine detected that there was a restriction in your breathing but not a full obstruction.

At some point flow limitations become severe enough to be hypopnea events which also are not full obstructions. Once breathing stops from obstruction, an obstructive apnea occurs.

A central apnea occurs when restriction isn't seen but the body does not breathe. Central apneas are the body not thinking it needs to breathe vs being obstructed.

Yesterday I saw this on YouTube: http://www.youtube.com/watch?v=-gie2dhqP2c. It's a pretty good, if not engaging, discussion on your question.

[jerryfudd]

I seem to only get central ones when I am awake with it on before falling asleep, like if I clear my nose or something?! I am getting pretty low AHIs normally now. From 0.5-3 max, usually around 1.

[jerryfudd]

That video is good! Thanks!

[palerider]

Think of a flow limitation as an almost apnea. It means the machine detected that there was a restriction in your breathing but not a full obstruction.

A FL is not an 'almost apnea', a FL is a reduction is airflow RATE whereas both hypopneas and apneas are reductions in airflow VOLUME.

Think of a FL as breathing through a straw, you can still get a full breath, but it takes more effort, leading to more fatigue, which will reduce your sleep effectiveness, as well as disturbing your sleep.

[khauser]

Think of a flow limitation as an almost apnea. It means the machine detected that there was a restriction in your breathing but not a full obstruction.

A FL is not an 'almost apnea', a FL is a reduction is airflow RATE whereas both hypopneas and apneas are reductions in airflow VOLUME.

Think of a FL as breathing through a straw, you can still get a full breath, but it takes more effort, leading to more fatigue, which will reduce your sleep effectiveness, as well as disturbing your sleep.

By "almost apnea" I meant that the FL is caused by a not-complete restriction in the airway. I don't disagree with your clarification, just wanted to explain the point of view I was expressing...

[Miss Emerita]

Hi all, still trying to get my head around flow limitation! Is it good that over time this has gone down?

Yes, the reduction is change in the right direction. When the flow rate is limited (see PR's image), you have to exert extra effort as you breathe, and over the course of the night, that can be quite tiring. It can also disrupt your sleep cycles. It seems that increasing the EPR from 2 to 3 was of some help to you.

You might see additional improvement if you ever shift from your current machine to a bi-level machine. That's why I now am using a VAuto. My pressure support is currently at 4.8, and that really brought my FLs down, as compared to EPR of 3.

[palerider]

By "almost apnea" I meant that the FL is caused by a not-complete restriction in the airway.

But, an "almost apnea" is, by definition, a hypopnea.

A Flow Limitation is a different thing.

As the video you found, (and I've posted repeatedly shows) there are four primary types of sleep disordered breathing, and they all are caused by a not complete restriction in the airway (even an apnea is defined as 90%+ restriction of air volume.)

[multicast]

A FL is not an 'almost apnea', a FL is a reduction is airflow RATE whereas both hypopneas and apneas are reductions in airflow VOLUME.

Think of a FL as breathing through a straw, you can still get a full breath, but it takes more effort, leading to more fatigue, which will reduce your sleep effectiveness, as well as disturbing your sleep.

Exactly: a flow limitation is a limitation of the flow in connection with a higher effort to breathe. Flow limitations are described as a dissociation between flow and the effort to breathe.

And the value between 0 and 1 must not be considered as a "percentage" how much the airway is obstructed, i.e., a metric value. It's an ordinal one, just like a grade, where a flow limitation of 0 correspond to an "A" whereas a value of 1 corresponds to an "F".

Mike