2022/06/28 by Donnelly, Chris, Schmitt, Sabine, Cecatto, Cristiane +5
paper · doi:10.26124/mitofit:2022-0025
Hypoxia is a condition of oxygen levels below normoxia and opposite to hyperoxia. We here define the normoxic reference state by three complementary precepts: (A) ambient normoxia at sea level in the contemporary atmosphere and corresponding dissolved O2 concentration at air saturation of aqueous environments; (B) biological compartmental O2 levels at ambient normoxia under physiological activity of healthy organisms in the absence of environmental stress (e.g. in a diving human, a stranded whale, a thermally stressed animal); and (C) O2 levels above the control region, i.e., where the capacity for O2 consumption is not compromised by partial O2 pressure as evaluated by its kinetics. Conversely, the abc of hypoxia is concerned with deviations from these reference points caused by different mechanisms: (a) ambient alterations of oxygen levels; (b) biological O2 demand exceeding O2 supply under pathological or experimental limitations of convective O2 transport or O2 diffusion; and (c) critical oxygen pressure in oxygen kinetics shifted by pathological and toxicological effects or environmental stress. The ABC of hypoxia may be of help in the design and interpretation of in vitro and in vivo experimental studies.