The machine can't tell the difference. You might get some sort of clue from looking at the breathing patterns and the shape of the waveforms, but it's iffy.
The medical community used to sort of assume hypopneas are all obstructive. They've begun to entertain the idea of central hypopneas in the past few years. I think it's still sort of up in the air whether there are central hypopneas and how to distinguish one from the other.
Yet another reason you need a fully data capable machine with airflow waveforms and need to review the data.
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If it's midnight and a DME tells you it's dark outside, go and check it yourself.
11-11-2015, 01:25 PM
(This post was last modified: 11-11-2015, 01:27 PM by justMongo.)
(11-11-2015, 12:22 PM)spottymaldoon Wrote: Archangle: Interesting - from what people are saying, modern machines can record breathing patterns - does this pick up "shallow" breathing or "lazy diaphragm" events? I was contemplating trying a strain gauge/belt to do this but if the machines can do that now I'll trade in my old one.
Today's machines sample flow at about 25 samples per second. The normal shape of the inhalation waveform rises to a rounded peak, then falls with roughly the same shape. When the airway is partially restricted the top of the inhalation waveform becomes flattened. ResMed scores Flow Limitation by that shape. Flow Limitation is often a precursor to OA or HA.
Machines can certainly measure shallow breathing because they integrate the area under the flow curve to calculate Tidal Volume (VT) which is in the neighborhood of 500 ml. It does not flag a 300 ml VT as shallow as it may be normal for a person.
A decrease in flow by X% for Y seconds does flag as a hypopnea.
(I have forgotten X and Y.)
There is no scoring for lazy diaphragm. Except perhaps in the brass section of a band.
And, your leak rate is too high.
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.
11-11-2015, 06:06 PM
(This post was last modified: 11-11-2015, 06:21 PM by zonk.)
I don't know about M series auto but the S8 AutoSet didn't increase pressure to treat apnea above 10 to avoid runaway pressure and causing central events. But increase pressure in response to snoring and flow limitation up 20 which are considered signs of obstructive events (not central events). ResMed S9 AutoSet and AirSense 10 AutoSet, PRS1 Auto 50/60 series and DreamStation Auto ... can distinguish between obstructive and central events and doesn't increase pressure in response to central events whenever detected
When I first used S8 AutoSet, Hypopnea numbers, always seem on the high side but the S9 AutoSet amd later AirSense 10 AutoSet took care of it, AHI numbers come down to below 1 and stayed like that to this very day ... YMMV