Frequently asked questions in hypoxia research

“What is the O(2) concentration in a normoxic cell culture incubator?” This and other frequently asked questions in hypoxia research will be answered in this review. Our intention is to give a simple introduction to the physics of gases that would be helpful for newcomers to the field of hypoxia research. We will provide background knowledge about questions often asked, but without straightforward answers. What is O(2) concentration, and what is O(2) partial pressure? What is normoxia, and what is hypoxia? How much O(2) is experienced by a cell residing in a culture dish in vitro vs in a tissue in vivo? By the way, the O(2) concentration in a normoxic incubator is 18.6%, rather than 20.9% or 20%, as commonly stated in research publications. And this is strictly only valid for incubators at sea level.