Oxygen Can Remedy the Effects of Long Term Covid
 
Long-term covid is characterized by exercise intolerance.  Intermittent, supplemental oxygen can alleviate that condition by getting oxygen to the organs, oxygen that has been cut off by vascular insufficiency.  Viruses can have the effect of deteriorating the vascular infrastructure between the heart and the lungs.
 
This vascular deterioration cannot be seen with standard heart function testing.  It can only be seen by an invasive test that measures the amount of oxygen being transmitted between the heart and lungs during exercise.  A test so dangerous that when my mother had the test many years ago, the man who had the test before her died during the test, then she had to go in to have the same test.
 
70% of the heart disease in the world is not adequately diagnosed, properly understood, or treated.  This is because the gold standard for heart diagnosis, the standard stress test, diagnoses heart blockages but not exercise intolerance.   Chronic fatigue, long term Covid are not diagnosed by any of the following standard hearth disease tests. 
 
Current Heart Patient Initial Evaluation Testing:
Extensive blood work
Pulmonary function testing
Echocardiography
Cardiac catheterization
Radiographic imaging
Nuclear imaging modalities
Cardiac stress testing
Cardiopulmonary exercise testing (CPET) is noninvasive, not invasive catheterization,  just stress test exercise machine 
Source:  WinterGreen Research, Inc.  
 
Patients may undergo 20 or more tests as per the above list with no definitive diagnosis.  These tests do not show that under conditions of intense exercise the blood vessels and arteries between the heart and lungs may not properly oxygenate the organs, leading to fatigue during exercise.
 
Only the iCPET that uses a metabolic cart instead of a pulse oximeter is able to diagnose PAH definitively.  The PAH diagnosis from iCPET is definitive enough of PAH to get insurance reimbursement for chronic fatigue syndrome, while the other tests listed above do not provide a definitive diagnosis and patients do not get disability insurance.