Measuring cerebral hypoperfusion with Doppler ultrasound

I think you may have misunderstood the context of what I said. As indicated to Hutan, I suspect things are complicated.

I am quite certain ME/CFS is almost always associated with OI. The discussion of blacking out on standing was in response to Jem's question. I am not sure that it has much to do with the origin of OI in ME/CFS.

I have never seen a tilt table test being performed but it sounds a fairly artifactual exercise that nobody would normally put themselves through. Like the CPET test it may lead to conclusions about the origin of symptoms in real life in ME/CFS that are misleading.

It looks from some graphs as if cerebral flow may decline gradually over many minutes in some cases. That looks to be quite different from the drop in flow that a normal person like me gets on standing. I mentioned the shift in plasma protein and wonder if there is a failure to retain fluid in the blood compartment over several minutes.

I see a problem with making use of evidence on individuals in different contexts to try to build a simple story when it may be much more variable and messier. That may include a significant exacerbation of the problem for some people from spending a lot of time lying flat.

We know for a fact both that OI tends to make you lie down and lots of lying down tends to lead to OI. So it isn't going to be simple.

 

That may be a good analysis. At present I am focusing on the issue of managing OI and potential cerebral hypoperfusion in the context of very severe patients unable to eat and needing nasogastric feeding and trying to put out a viewpoint document on that. It is a problem that has been followed by some very bad outcomes, as we all know. We need evidence and not evidence dressed up by physicians or physios with private practices to sell a point - not saying that that applies here but so often it does. And so many of these studies turn out, if you look, to be retrospective - which tends to spell bad news.

But I think it may be of some relevance to quite a large number of people severely affected and needs to be considered carefully.

 

One of the issues is that the presentation in severe and very severe ME is different to run-of-the-mill OI. Normally it's described as starting to feel ill after less than a minute of standing upright and still, but in severe ME, people start to feel ill as soon as they sit up.

It'd be interesting to know whether people with non-ME related OI experience that. I didn't in the years before I got ME, and although the OI got worse with the illness, I've still never had it from sitting upright.

 

When my sister, who has always been perfectly healthy (no ME/CFS, LC or anything else), was a teenager there was a time where she would blackout and faint. After this had occurred a few times my parents went to see a doctor, especially due to the significant dangers when you’re falling on your head after fainting. The doctor seemed very familiar with this phenomenon and just advised her to stand up slower. It seems that simple trick resolved all issues and my sister has long since outgrow those problems (or perhaps has become accustomed to standing up slower). I can't imagine that there was ever a time in which my sister and probably that doctor would have thought that was worth any diagnostic label such as OI, as everything was easily avoidable by getting up slower, nor did she ever feel ill in upright position. Essentially there is nothing worth discussing.

However, if someone is conducting a study purely based on measurements of heart rate and blood pressure this could probably fall under the category “feeling ill as soon as they stand up”, but has no relation to ME nor does it seem worthy of being investigated, even though I'm assuming it would also show up on a TTT in some form or another. So there's probably these rather meaningless phenomena one has to be aware of when looking at people "feeling ill as soon as they sit up" to make sure one isn't studying noise or simply a different phenomena than the one that one actually wants to study.