Head hypoperfusion and pulse oximeters

[GasconAlex]

After seeing a huge decrease in saturation O2 in my fingers by raising them from lying down about 30 cm above heart level (drop from 95% to 80% or lower) above this level (arm raised straight up from lying flat on bed) my pulse oximeter cannot find a pulse so I could not compare further. The exercise didn't alter my pulse really at all. I then tried to use the oximeter on my ear - where I was able to get comparable readings as to those on my finger (I used a mirror to read the result).

This is where it gets more interesting. When standing I got the pulse rate bump of about 30 BPM but although still consistent on pulse readings the ear spO2 dropped to around 80%. I tried a couple of times, the values varied but were always around 80% +- 3/4%.

Looking around on the use of finger pulse oximeters on ears I came across this The Ear as an Alternative Site for a Pulse Oximeter Finger Clip Sensor which concludes that it is unsuitable as the ear varies beyond acceptable bounds with the ear over reading spO2 which could be dangerous in monitoring, missing hypoperfused patients.

So does this indicate cranial hypoperfusion on standing, and does it happen to other people who suffer either orthostatic intolerance or POTS?

If you have a pulse oximeter and can get a consistent reading on your ear I'd like to know if this is generalised, just me or if there is research out there on this. 

 

 

[Pistol]

In the medical field they prefer the use of finger sensors for PO2 readings. They will use the ear if there is not adequate circulation in the fingers but it is not accurate. It is not uncommon to have decreased PO@ readings when raising your arms above your head - that is not usually done or recommended while attempting to get an accurate PO2 reading. It is completely normal to loose some degree of circulation when extending your arms above you heart since it alters the rate of how efficiently your veins can pump the blood upwards. Therefore any readings taken by any probes in that position will not reflect true readings.  

[GasconAlex]

As link says the ear use is inaccurate as tends to overestimate the spO2. Not underestimate.

The second point is raising arms might well reduce flow, but if everything is going well this cannot be the case for the head, as this is the default position, thus any veinous effects should be null.

Your points are valid, but do not explain a reduced spO2 reading whilst standing on an ear reading except if there is an effect from reduced O2 due to position. If the ear gets less O2, presumably the brain does too.

Lastly although the research points out inaccuracies in readings on the ear, this is of the order of a % or 2, not 15%.