Systemic enzyme supplements have many benefits for chronic fatigue patients. They can improve blood flow by removing fibrin (protein involved in blood clotting) from the blood, reduce inflammation, and help digest food.
Certain doctors like Dr. David Berg believe that CFS patients are in a hypercoagulable state. And that people with CFS and FMS have a genetic predisposition towards a hypercoagulable state. So, a reduction in coagulation by the use of systemic enzymes could help improve blood flow.

In a study from 1998, 16 CFS and FMS patients were given daily injections of Heparin (a blood thinning drug). 8 of these patients experienced significant improvement, and 7 experienced moderate improvement. So, increasing blood flow by thinning the blood, may lead to a reduction in symptoms.

Systemic enzymes are one of the supplements that helps my brain fog the most. If im feeling bad on a particular day, i just take an extra enzyme pill and that helps to relieve my brain fog for the day. The enzyme supplement that i take is called vitalzym. It contains the enzymes: protease, serrapeptase, papain, bromelain, amylase, lipase, rutin, and amla.

A recent study found that a certain subgroup of CFS patients may have a disordered breathing pattern, and might benefit from breathing retaining. 5 out of the 20 subjects that they studied had an asynchronous breathing pattern and could correct it with retraining. The study did not say whether there was any improvement in symptoms once this correction was made.

There also have been other breathing issues found in patients. Such as the feeling of “air hunger” or sleep apnea.

The feeling of air hunger or not feeling like you can get a full breath of air is often found with the co-existing problem orthostatic hypotension. In this case the body isnt keeping maintaining adequate blood flow, and the body feels starved for oxygen.

Sleep apnea is another breathing problem which may be common in CFS patients. It is a disorder in which a person take long pauses between breaths during sleep. This can occur many times thoughout the night and can caused lower oxygen levels in the blood. Daytime fatigue and concentration difficulties can result from sleep apnea.

For a subset of patients, breathing disorders like sleep apnea may be the cause of their chronic fatigue. But many times it is another symptom.

Also here is a post by a forum member that has recently been diagnosed with a breathing disorder.