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MTF Carter

Development Team Member
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Posts: 27
 #1 
We have been using the gardner walking treadmill protocol as a screening tool in patients with peripheral artery disease (PAD). I noticed during a screening visit that upon standing the SmO2 dropped very low in the right leg of the patient (ABI=0.8) I suspect this is due to orthostasis. However, the drop in SmO2 seems too large to account for a simple relocation of volume.

Here is the data... the first big drop in SmO2 is the subject standing and is the area I am talking about for this post. the next big drop ar mins 0:29:00 is the start of the walking protocol that 2.0 mph with an increasing incline by 2% every 2 mins until fatigue.  SmO2 in Red tHb in blue. this is the entire screening study that lasts over 1 hr.
PAD Walking.JPG  Here is the data zoomed in so you can see what happens in PAD when you stand up. walk 2.JPG 
So I tried this in myself to see... I was supine for about 5 mins. then sitting for another 5 mins. I stood up for 30 seconds. the SmO2 increases and then falls when I sit back down. I don't know if my 30 second stand was long enough so the next time I stand until the SmO2 data is steady. SmO2 in my leg with no PAD (ABI= 1.0) only dropped to 55. then SmO2 starts to climb back up.
JCL stand.JPG 
 In normal people the autonomic nervous system mediates an orthostatic response that raises heart rate and peripheral vascular resistance and thus tends to restore mean arterial blood pressure. in terms of O2 extraction, greater flow supplies more O2, so the tissue needs to extract a smaller fraction of the incoming O2 to satisfy its fixed needs.

My questions are
1. Why is the SmO2 dropping so low in PAD if flow is technically greater from a gravity?
2. If I have a PAD patient stand for a longer period of time would they have the same autonomic response?

I will try to look into this more as time permits...but I will admit my free time is basically 0 now that I'm on the cardiology call service haha!

juergfeldmann

Development Team Member
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Posts: 1,501
 #2 
Did  you do this  whit MOXY  because we  can show  nicely  in some cases  what happens  when we   use  O2Hb  and HHb  biased  at the specific  section. if  yes  sent the  csv on my  email  as it is a patients   data.
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