Cell hypoxia is one of the main causes of free radical generation and oxidative stress leading to inflammation, especially in the capillaries. Capillaries are critical determinants of oxygen and nutrient delivery and utilization so inflammation there is telling.
Just so happens that normal arterial levels of CO2 have antioxidant properties. A group of Russian microbiologists discovered that "CO2 at a tension close to that observed in the blood (37.0 mm Hg) and high tensions (60 or 146 mm Hg) is a potent inhibitor of generation of the active oxygen forms (free radicals) by the cells and mitochondria of the human and tissues."
Dr. L.O. Simpson asserts that Fatigue Immune Deficiency Syndrome (CFIDS), results from “insufficient oxygen availability due to impaired capillary blood flow.” Tissue oxygenation is severely disturbed during pathological conditions such as cancer, diabetes, coronary heart disease, stroke, etc., which are associated with decrease in pO2, i.e. ‘hypoxia’. Oxygen delivery is dependent on the metabolic requirements and functional status of each organ. Consequently, in a physiological condition, organ and tissue are characterized by their own unique ‘tissue normoxia’ or ‘physioxia’ status.
Biologist Dr. Ray Peat tells us that, “Breathing pure oxygen lowers the oxygen content of tissues; breathing rarefied air, or air with carbon dioxide, oxygenates and energizes the tissues; if this seems upside down, it’s because medical physiology has been taught upside down. Respiratory physiology holds the key to the special functions of all the organs, and too many of their basic pathological changes.”
Every cell in our body can recognize and respond to changes in the availability of oxygen. The best example of this is when we climb to high altitudes where the air contains less oxygen. The cells recognize the decrease in oxygen via the bloodstream and are able to react, using the ‘hypoxic response,’ to produce a protein called EPO (erythropoietin). This protein in turn stimulates the body to produce more red blood cells to absorb as much of the reduced levels of oxygen as possible.
 Izv Akad Nauk Ser Biol. 1997 Mar-Apr;(2):204-17. Carbon dioxide–a universal inhibitor of the generation of active oxygen forms by cells (deciphering one enigma of evolution). Article in Russian
 J Cell Mol Med. 2011 Jun; 15(6): 1239–1253. Why is the partial oxygen pressure of human tissues a crucial parameter? Small molecules and hypoxia