"Cerebral blood flow is reduced in ME/CFS during head-up tilt testing even in the absence of hypotension or tachycardia... van Campen et al, 2020

David Bell found low blood volume in ME patients. He gave them IV saline and they felt normal almost at once. Unfortunately the effect wore off and the treatment had to be repeated weekly.

This is another area of research that was ignored rather than disproved.

 

There was a Canadian study that found reduced brain blood flow during exercise. I would need to dig for the paper, it may have been in the 1990’s.

 

This one?
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1475-097X.2008.00822.x

 

There have been some studies of total blood volume in patients (don't have links at hand though).
And sadly those who get saline weekly sometimes report that they benefits wear off over time as though the body gets habituated to the infused saline but doesn't respond as it had initially.

 

Those researchers may not have been wrong, hyperventilation does often occur and respiratory physios can be quite useful in correcting disordered breathing. Its a very common finding in POTS patients and learning to fight your broken respiratory drive can limit symptoms and give you more time on your feet. The important distinction to make is that the hyperventilation has a physiological root cause and not a psychological one. I've found doctors either don't have the time or the empathy to stress these sorts of distinction, so the patient can go away feeling fobbed off.

It seems like relative hypovolemia is important too. You can have a normal absolute blood volume (or correct towards normal), but if neuropathy or some other factor is causing splanchnic or peripheral pooling the end result will be similar.

 

https://www.ncbi.nlm.nih.gov/pubmed?Db=pubmed&Cmd=ShowDetailView&TermToSearch=9731612


CONCLUSIONS:
Cerebral vasoconstriction occurs in OI during orthostasis, which is primarily due to hyperventilation, causing significant hypocapnia. Hypocapnia and symptoms of orthostatic hypertension are reversible by CO2 rebreathing.

 

Hi @lunarainbows,

Upon standing its normal for your blood distribution to shift, as its pulled downwards by gravity. In a healthy person mechanisms kick in to correct this change and bring blood pressure and flow rates back to (near) normal and keep your blood where its supposed to be. Central hypovolemia refers to when blood has moved away from where its needed towards the periphery, there are a number of overlapping reasons why the normal corrective mechanisms haven't worked and how this might perpetuate.

There are a number of drugs that can really help restore what seems to be best described as the resulting pre-load failure, i.e. the heart not getting enough blood returned to it. I have found great success from Ivabradine and Pyridostigmine. Others find Midodrine and Fludrocortisone very helpful. Equally people can find compression garments make a huge difference. It all depends on what underlying causes you have for your OI and their significance.

Hope that helps,
Ryan

 

Unfortunately, both were well-regarded in ME/CFS circles as good guys.

 

I'm sorry, but I have difficulty buying into that.

 

I'd know if I were hyperventilating. And if I can learn how to breathe "correctly", isn't that at least a little suggestive that I learned how to breathe incorrectly? Perhaps not, but somehow I always thought this was a tad victim blaming, even if inadvertent.

 

Hi @duncan,

It was my experience that I did not know I was hyperventilating. Hyperventilation does not require you to be breathing in a fast, panicked manner as the layperson understands it. I was shown to be breathing very calmly, slower than average in fact, just excessively deeply (during tilt table, CPET etc.). When used scientifically the term just means excessive respiratory minute volume for your metabolic demand, it implies nothing else with regards to method or cause (there are many).

My respiratory drive is malfunctioning, a result of underlying physiological mechanisms that occur on orthostasis that have nothing to do with psychology. These mechanisms are fairly well established in the POTS research. Behaviourally 'correcting' (really just 'compensating') means fighting the inappropriate urges that my respiratory centre gives me to breathe more than necessary when standing, which helps control resulting hypocapnia and the acceleration/worsening of symptoms. There's no implication that I had done anything wrong to find myself in that state, in a similar way that I had done nothing wrong to make my heart rate jump.

It unfortunately gets messy when the physician doesn't take the time to explain all this, which understandably makes the patient think they're being lumped in with anxiety-type hyperventilation. The layperson misunderstanding of the word doesn't help either. And of course there's precedent for the unaware and uncaring doctors to just jump to psychological conclusions and dish out those anxiety diagnoses without understanding what is actually happening.

Ryan

 

To give a clear example of how hyperventilation doesn't necessarily imply psychological cause: patients with mitochondrial myopathy hyperventilate as a response to the lactic acidosis they experience after exertion.

 

What a clear and thoughtful explanation. Thank you for taking the time.

So, they need to pick a better word. Of course, we should be used to words that can be misused or...have onerous meanings and baggage with regard to us.

Again, I appreciate you taking the time to share that.

 

Thank you - yes that makes sense.

 

This conclusion would seem to be contradicted by a more recent study Ryan referenced above which suggested that orthostatic hyperventilation comes after.

https://doi.org/10.1161/hypertensionaha.113.02824

 

A lot of research is being done on dry eyes so the basic biology of how the eye makes adjustments is being worked out. It is only when you think about it you realise how much is going on.

When they try new treatments they often work for a while then the body gradually resets to the previous level which is very frustrating.

From this and other things I have read I think there is a system in the brain and nerves which is overlooked. It is trained to detect the normal point round which homeostasis works but it can go wrong. In the same way that the immune system is trained to detect the self but goes wrong and you get autoimmune disease, it is not much of a stretch to believe that the level of "normal" function can go wrong.

The FND people get close to this but they have the wrong emphasis and are holding back what could be important and useful research.

 

Commentary
​

Nutshell: The study found that 89% of ME/CFS patients had symptoms of orthostatic intolerance in everyday life, such as feeling very tired or lightheaded on standing,. Almost half of these had classical signs of orthostatic intolerance, unusually low blood pressure on standing or increased heart rate. However, just over half did not. Using an "improved", but not yet independently validated approach, the authors found is that blood flow to the brain was reduced in almost all patients with OI, regardless of heart rate/blood pressure changes.​

Some of these points have already been made on this thread, particularly by @Dolphin.

Why they did the study

It's worth understanding why the authors have done this study, using a new technology, but there's quite a lot of information here and I put it in a quote box.

What the study found

The authors analysed data on 429 patients who underwent the test out of the total of 675 patients diagnosed with ME/CFS. (The reason for excluding other patients, including because they underwent a different kind of test for good reasons, all seemed fair enough to me.) And that makes this one of the very biggest ME/CFS patient cohorts ever to feature in a research study

86% of ME/CFS patients had daily life orthostatic intolerance symptoms as assessed by questionnaire. That's a pretty high figure. The authors concede that the figure might be too high because of referral bias, where physicians are more likely to refer patients with OI to the clinic used by the authors (presumably they are specialists in OI). On the other hand, the authors also point out that they didn't include bedbound patients, who are more likely to have OI, and excluded severe patients from the test because they thought it would be too stressful for them. That could lead to an underestimate. Potentially it’s swings and roundabouts. At any rate, 86% is probably the most robust estimate we have of OI in ME/CFS patients.

Of the patients with OI symptoms, almost half (48%) had either an abnormally high heart rate on standing (postural orthostatic tachycardia syndrome, POTS) or blood pressure that dropped unusually far on becoming upright (delayed orthostatic hypotension). The other half (52%) had normal blood pressure and heart rate response to standing (where blood pressure might drop a little and heart rate goes up a bit, as it does in healthy controls).

For the 52% of patients who had normal heart rate and blood pressure responses but also had OI symptoms, 82% of these showed an abnormally large reduction in CBF (a 24% drop compared with a 7% drop for healthy controls).

So it appears that for the 82%, their OI symptoms might well be due to reduced blood flow to the brain, even though their heart rate blood pressure responses to standing are normal. Which confirms the authors' basic hypothesis.

Further support for the role of CBF in OI symptoms was the moderate correlation between the number of OI symptoms recorded during the tilt test and the degree of CBF. The authors actually described this as a strong correlation because of the low P-value, but the correlation of R = 0.4 can only really be described as moderate (see diagram below).

What does it all mean?

Although at one point the authors got carried away and said their data shows CBF causes OI symptoms, they don't include that claim in the conclusion or the abstract. They have shown an association between CBF and OI symptoms, which is very interesting all the same.

As the chart below shows, the correlation between symptom count and CBF isn't that amazing. Incorporating symptom severity as well may have given a stronger correlation. Or perhaps the true correlation really isn't that strong.

​

Also, 10% of patients who didn't have orthostatic intolerance symptoms had either POTS or delayed orthostatic hypotension. And some with OI symptoms show normal CBF response on standing.

In short, the authors' comments in the introduction  that “part of OI symptomology is related to" cerebral blood flow is probably a fair summary.

It is worth noting that the authors have developed a new technique here which, as they point out, needs replicating/validating by others.

Also, some traditional Doppler blood velocity measurements do support reduced blood flow in other types of patients with orthostatic intolerance. In other words, this effect is not unique to ME/CFS patients. Perhaps a more interesting question is, "why do so many ME/CFS patients have OI symptoms"?

I think Lucinda Bateman has commented that OI symptoms are highly treatable, which should be good, but I don't think this has been proven in clinical trials and, anecdotally, it seems to be a mixed picture for patients who have tried relevant medications.

 

I've been tested twice for hyperventilation 20 odd years apart and was cleared both times. Have had POTS since a teenager.

Not been tested after exercise so it may be that I do hyperventilate in those or other unknown circumstances but on a "normal" day it doesn't seem to be a cause behind my POTS and symptoms.

 

That is a confusingly worded conclusion. They cannot suggest that OI is caused by hyperventilation, (because their study did not show that - participants were told to hyperventilate), they instead demonstrated that hyperventilation contributes to cerebral vasoconstriction and hypocapnia. CO2 rebreathing can help, simply because it can lead to subsequent cerebral vasodilation. Their study doesn't really demonstrate why there is an excessive cerebral vasoconstriction response in OI patients, given no change in, or a reduction of systemic resistance due to hyperventilation.

 

Its definitely not the case that 100% of POTS patients hyperventilate, its just a contributing factor in some cases (as with practically all POTS patients there are different but overlapping contributing factors).

You could also argue that if you were not standing much either before or during the investigation (depending on what they choose to do, ABG, voluntary hyperventilation monitoring etCO2 etc.), you would get a false negative. Even the time of day can make a big difference when it comes to POTS investigations.

If you're interested there was a recent study that David Systrom was involved with that tried to group patients by characteristics like HV, mito dysfunction and a couple of other issues. Unsurprisingly the patients that had collected multiple characteristics were generally worse off than those with only one or two.