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+--- Thread: Still trying to understand this machine (/Thread-Still-trying-to-understand-this-machine)
Still trying to understand this machine - SailingAway - 03-06-2015
I have seen the videos showing a clear airway apnea vs an obstructive apnea. I don't understand, when looking at the charting in SH, what the machine sees to determine whether CA or OB. Below is a chart of two of them close together from last night and can someone please explain to me what causes it to be labeled one or the other.
![[Image: RAFlq7m.png]](http://i.imgur.com/RAFlq7m.png)
I see the machine do it's thing, testing the airway, but I don't see what it sees to make the call. These aren't the best examples they just happen to be in the same frame here for ease of comparison.
RE: Still trying to understand this machine - archangle - 03-06-2015
(03-06-2015, 12:35 AM)SailingAway Wrote: I have seen the videos showing a clear airway apnea vs an obstructive apnea. I don't understand, when looking at the charting in SH, what the machine sees to determine whether CA or OB. Below is a chart of two of them close together from last night and can someone please explain to me what causes it to be labeled one or the other.
The information it uses to determine CA vs. OA is probably not in the graphs.
Google "Forced Oscillation Technique."
FOT sends a series of short pulses of pressure and measures the resulting changes in airflow to tell whether or not it's "working" against an air blockage in your throat, or if it's working against your lungs.
The "hairy" spot on the blue mask pressure line is where it's applying FOT. The magnitude and frequency of the air flow response is such that you can't see it on the flow rate graph, but the machine probably uses signal processing to measure it.
RE: Still trying to understand this machine - quiescence at last - 03-06-2015
so, you actually can see this in your provided chart. when FOT occurs on the first apnea, the flow rate does not jiggle. on the next application of FOT the flow rate does jiggle, indicating there is no resistance to flow.
so this snapshot has captured the difference perfectly. nice job.
QAL
RE: Still trying to understand this machine - SailingAway - 03-07-2015
Hope this doesn't violate some rule. Since it is a machine manufacturers site and in the interest of education.....
http://www.resmed.com/int/assets/documents/product/s9_series/1013916_s9-autoset_white-paper.pdf
The first four paragraphs of this white paper seems to explain it very well. Says the same thing quiescence said in the prior message. I think I have it now for the most part. Still not clear on how the machine measures flow limitations. Seems like it will mark a limitation well below whatever the total flow capability of the machine, which it should. Would seem to me that the limitation would be me trying to get breath, but being unable to do so. I would think that there would need to be drop in mask pressure, not related to a leak with the machine trying to supply the need, but not being successful. Is that correct?
RE: Still trying to understand this machine - Evpraxia - 03-07-2015
SailingAway,
You have excellent questions; I have wrestled with these as well. I will keep reading and learning.
Thanks for asking!
RE: Still trying to understand this machine - DeepBreathing - 03-08-2015
(03-07-2015, 01:33 PM)SailingAway Wrote: Hope this doesn't violate some rule. Since it is a machine manufacturers site and in the interest of education.....
http://www.resmed.com/int/assets/documents/product/s9_series/1013916_s9-autoset_white-paper.pdf
That's quite ok. Links to manufacturer's sites are explicitly permitted provided they don't sell to the public from the site.
RE: Still trying to understand this machine - archangle - 03-08-2015
(03-07-2015, 01:33 PM)SailingAway Wrote: The first four paragraphs of this white paper seems to explain it very well. Says the same thing quiescence said in the prior message. I think I have it now for the most part. Still not clear on how the machine measures flow limitations. Seems like it will mark a limitation well below whatever the total flow capability of the machine, which it should. Would seem to me that the limitation would be me trying to get breath, but being unable to do so. I would think that there would need to be drop in mask pressure, not related to a leak with the machine trying to supply the need, but not being successful. Is that correct?
A flow limitation is usually a case where your airway is narrow enough to offer resistance to your airflow. Think of it as being like having a stuffy nose that you can still breathe through. This is often caused by the same effect as an apnea, but your airway doesn't close up as much. Flow limitations also can go on for a long period of time.
Without flow limitation, your airflow will be a smooth sine wave looking waveform. With flow limitation, as you inhale, your airflow goes up part way, but then doesn't get any higher. Your airflow will look like a square wave on the top.
Exhales tend not to have flow limitations (or obstructive apneas) because any blockage of the airflow increases the pressure in your airway and opens it up, sort of like CPAP does.
In my opinion, flow limitations aren't as well understood or quantified to the same degree as apneas or hypopnea.