Flow limitation and minute ventilation-I have tried to research these two types of data, but i do not seem to get an easy definition that tells me whether mine is good or bad. I have been using a Resmed Autoset for about three month with what looks like pretty good results.
My AHI began at around 5 and now is often less than one, sometimes on a bad night maybe 2 or three. All of the data makes good sense except for these two things. The discussions i've read seem to be very technical but i still don't know what a good or bad one looks like or what it means.
Can someone give me a very plain description of what i should look for?
11-16-2013, 04:26 PM
(This post was last modified: 11-16-2013, 04:31 PM by robysue.)
Minute ventilation is just the total volume of air inhaled (or exhaled) in one minute. In other words, you can think of it as the sum of the total amount of air you inhaled in each individual inhalation over the course of one minute. "Normal" minute ventilation (MV) values vary widely based on physical size of the person and also on what the person is doing at the time you measure the MV. For a typical sized adult at rest, the MV is usually between 5 and 8 Liters at rest while awake. During sleep the MV is typically less than it is while resting while awake. From what I've read, MV during sleep is often 10-15% below normal "wakeful resting MV values".
Flow limitation is a change in the shape of the inspiratory part of the wave flow that indicates the upper airway may be slightly compromised or may be starting to collapse. The S9 uses a proprietary algorithm for analyzing the shape of the inspirations in the wave flow and "scores" the inspirations to create the Flow limitation graph. In general, the higher the flow limitation graph, the more "unhappy" the S9's algorithm is with the shape of the inspiration in the wave flow and the more likely the airway is to be compromised. The S9's Auto algorithm will increase the pressure in response to the flow limitation curve going up (and the inspiration part of the wave flow becoming more distorted in shape.)
In general, there are no "normal" values for the Flow limitation curve. In principle, you'd like the flow limitation curve to stay nearly flat and as low as possible. In practice, how much you want to worry about the flow limitation curve strongly depends on how much the flow limitations seem to bother you (their clinical significance is still somewhat controversial), how much additional pressure is needed to smooth out the flow limitation curve, and how much that additional pressure winds up bothering you in terms of the quality of your sleep. For me? It's easier to put up with some raggedness in the flow wave and some (additional) flow limitations being scored by my PR System One than it is to try to put up with the additional pressure needed to eliminate them.
11-16-2013, 04:42 PM
(This post was last modified: 11-16-2013, 04:44 PM by drgrimes.)
Robysue thanks for the concise definitions. How do i know if mine is good or bad? My AHI is typically less than one. I will attempt to attach a screen shot in here of my Minute Ventilation. THANKS!!
Hmmm seems that i did not attach an image.....have to learn how....quickly LOL