Question

I know there has been some interesting research involving neuroimaging studies and that this has demonstrated defects in blood flow to certain key parts of the brain. But does this research mean that people with ME/CFS have low levels of oxygen entering the brain? If so, does it also explain some of the key brain symptoms – cognitive dysfunction in particular? And could it lead to new forms of drug treatment?

Answer

People get the oxygen they need by breathing air into the lungs. Oxygen is then extracted and carried in the blood in two forms. The majority of oxygen is bound to hemoglobin within red blood cells, while a small amount of oxygen is physically dissolved in the plasma. Red blood cells, also known as erythrocytes, deliver oxygen to cells via the heart. Oxygen helps cells grow, reproduce, and break down food in order to get the energy we need to survive.

There are a number of strands of ME/CFS research that clearly indicate problems with blood flow to various tissues and organs in the body. For example:

1. Dysfunction of the autonomic nervous system (ANS)
The ANS helps to control heart rate and blood pressure but also affects the diameter of blood vessels and causes excessive blood vessel constriction in cold weather leading to the cold hands and feet that are very common in ME/CFS. The ANS also controls blood flow to other tissues, including skeletal muscle, and it has been suggested that this could be linked to muscle fatigue and pain.

2. Cerebral blood flow:
There are a number of neuroimaging/brain scan studies using what are called SPECT scans, which have demonstrated decreased blood flow to specific areas of the brain. These findings suggest that hypoperfusion (decreased blood flow) of the central nervous system, including a key part known as the brain stem, may be playing an important role in the pathophysiology of ME/CFS, especially in relation to cognitive dysfunction (i.e. problems with memory, concentration, etc).

As oxygenation of tissues is linked to blood flow, decreased blood flow could, in theory, be causing less oxygen to reach vital tissues. In addition, there are the very interesting cardiopulmonary (i.e., heart and lungs) exercise studies from VanNess et al. in America that also indicate problems with oxygenation. Unfortunately, knowing that there are problems with blood flow, and possibly defective oxygenation of organs and tissues as a result, does not take us very much further as far as drug treatment is concerned.

There are drugs called vasodilators, which can help to dilate blood vessels. Nimodipine is one such drug, but there is no convincing evidence so far that they are of benefit in ME/CFS. Equally, there are a number of far more speculative and controversial treatments – such as hyperbaric oxygen therapy and so-called ‘bottled oxygen' and ‘ozone' – that are promoted to and used by people with ME/CFS. But the evidence here is also lacking.

The NHS

Home oxygen therapy | August 2020

See also: Cardiopulmonary Exercise Testing (CPET).

More information

• The ME Association Clinical and Research Guide (The ‘Purple Book') summarises the research evidence for reduced blood flow in ME/CFS.