+- Apnea Board Forum - CPAP | Sleep Apnea (https://www.apneaboard.com/forums)
+-- Forum: Public Area (https://www.apneaboard.com/forums/Forum-Public-Area)
+--- Forum: Main Apnea Board Forum (https://www.apneaboard.com/forums/Forum-Main-Apnea-Board-Forum)
+--- Thread: Should one even care about the FL graph on ASV machine? (/Thread-Should-one-even-care-about-the-FL-graph-on-ASV-machine)
Should one even care about the FL graph on ASV machine? - Michaely6 - 10-26-2019
I know this has been discussed before about insane the flow limitation graph looks on Resmed Aircurve ASV but are these even real flow limitations? Every FL graph on the aircurve Asv looks so wild and out of control compared to Cpap and Auto Bipap (non asv machine). Should all Aircurve ASV users disregard the FL graph completely?
RE: Should one even care about the FL graph on ASV machine? - SarcasticDave94 - 10-26-2019
I'd say it's still useful but maybe not as much as it would on other machine types. I rarely look at my charts anymore, relying on feel much more than numbers. Admitted, I've been at this for 2 years and that time affords me with knowing what to expect with a fair amount of accuracy. It's probably your choice to assign value to the various OSCAR data segments to keep your therapy on track. For myself, I had to decide what helps and what didn't when it came to tracking and aligning therapy. Things that were identified as unhelpful were mostly disregarded so I can focus on the useful info.
RE: Should one even care about the FL graph on ASV machine? - Michaely6 - 10-26-2019
Nice post Dave. Is your FL graph on your ASV crazy and out of control also?
RE: Should one even care about the FL graph on ASV machine? - SarcasticDave94 - 10-26-2019
Actually I'd have to look to answer. Give me a bit and I'll see what I've got. Got some nephews at the house so I don't have PC access right now.
RE: Should one even care about the FL graph on ASV machine? - Sleeprider - 10-26-2019
Bonjour and I have discussed flow limitation on ASV at length, and concluded that it is a natural and nearly universal byproduct of machine initiated inspiration. As the ASV increases pressure support to assure minute vent during central events and hypopnea, it is the machine doing a significant part of the "work" of respiration. This machine triggered braath does not have the same characteristics and normal spontaneous inspiration. In normal breathing, the rib cage and diaphram is expanded to create negative pressure in the chest that allow air to fill the lungs. This gives the characteric inspiratory flow rate that rapidly accelerates to a peak flow rate until the lung is filled, then a rapid return to zero before expiration begins. With ASV, the machine is inflating the lungs and resistance increases as the lung fills. This gives a flow curve that looks flat or even downward sloping at the peak of inspiration, and is the criteria on which flow limitation is measured. The only way to overcome the decreasing flow rate as inspiration progresses would be an even more dynamic blower than is on the commercial market today, that would continue elevating pressure or affecting rise-time, to overcome resistance right up to the peak of inspiration. This does not exist, and I'm not aware of any research in that direction.
Machine triggered inspiration is invariably flow limited unless the patient assists in the inspiratory effort, due to increasing resistance as the lung fills and the chest must be expanded by the machine pressure support. I guess you'll just have to deal with it. More to the point, we have decided that flow limitation with ASV, ST and iVAPS therapy is not a sigificant or treatable parameter, so we will not recommend setting changes when it is observed.
RE: Should one even care about the FL graph on ASV machine? - sheepless - 10-26-2019
if yours looks like mine, the graph looks bad because it's full of 1.0 flow limitations. I've never confirmed because I couldn't figure out how to access the underlying data but wonder if the 1.0s are counted in statistics because I don't often see a 95% value. so it's my assumption that the 1.0s are caused by ca and my conclusion is to ignore the graph & watch the 95%tile figure.
RE: Should one even care about the FL graph on ASV machine? - Michaely6 - 10-26-2019
(10-26-2019, 09:29 AM)SarcasticDave94 Wrote: Actually I'd have to look to answer. Give me a bit and I'll see what I've got. Got some nephews at the house so I don't have PC access right now.
OK thanks
RE: Should one even care about the FL graph on ASV machine? - Michaely6 - 10-26-2019
(10-26-2019, 09:39 AM)Sleeprider Wrote: Bonjour and I have discussed flow limitation on ASV at length, and concluded that it is a natural and nearly universal byproduct of machine initiated inspiration. As the ASV increases pressure support to assure minute vent during central events and hypopnea, it is the machine doing a significant part of the "work" of respiration. This machine triggered braath does not have the same characteristics and normal spontaneous inspiration. In normal breathing, the rib cage and diaphram is expanded to create negative pressure in the chest that allow air to fill the lungs. This gives the characteric inspiratory flow rate that rapidly accelerates to a peak flow rate until the lung is filled, then a rapid return to zero before expiration begins. With ASV, the machine is inflating the lungs and resistance increases as the lung fills. This gives a flow curve that looks flat or even downward sloping at the peak of inspiration, and is the criteria on which flow limitation is measured. The only way to overcome the decreasing flow rate as inspiration progresses would be an even more dynamic blower than is on the commercial market today, that would continue elevating pressure or affecting rise-time, to overcome resistance right up to the peak of inspiration. This does not exist, and I'm not aware of any research in that direction.Is this also true with the flow rate graph itself on the aircurve Asv as well because some of the breaths on the actual flow rate graph appear to have the characteristics of a flow limited breath as well (non rounded inspiratory curve).
Machine triggered inspiration is invariably flow limited unless the patient assists in the inspiratory effort, due to increasing resistance as the lung fills and the chest must be expanded by the machine pressure support. I guess you'll just have to deal with it. More to the point, we have decided that flow limitation with ASV, ST and iVAPS therapy is not a sigificant or treatable parameter, so we will not recommend setting changes when it is observed.
RE: Should one even care about the FL graph on ASV machine? - Michaely6 - 10-26-2019
Thanks sheepless
RE: Should one even care about the FL graph on ASV machine? - Sleeprider - 10-26-2019
(10-26-2019, 09:48 AM)Michaely6 Wrote: Is this also true with the flow rate graph itself on the aircurve Asv as well because some of the breaths on the actual flow rate graph appear to have the characteristics of a flow limited breath as well (non rounded inspiratory curve).
If flow limitation is observed coincident to minimum pressure support, then increased minimum pressure support or higher EPAP min, might be considered to minimize that. I was mainly talking about those breaths where higher pressure support is doing the work of respiration.