Heat, infrared and the body's response
Tissue oxygenation
Tissue oxygenation is how much oxygen actually reaches the cells of a tissue. It depends on three things: how much oxygen the arterial blood carries, how fast that blood flows, and how far the oxygen must diffuse. It is not the same as blood oxygen saturation.
Also called oxygen delivery, tissue oxygen tension, PtO2
Oxygen delivery to a tissue is roughly blood flow multiplied by the oxygen content of arterial blood. Oxygen content is dominated by haemoglobin: how much there is and how saturated it is. Only a small fraction travels dissolved in plasma. Whether that oxygen then reaches a given cell depends on capillary density and diffusion distance.
A useful distinction. The reading on a fingertip pulse oximeter (SpO₂) is arterial haemoglobin saturation. It is not tissue oxygenation. Tissue oxygenation is measured quite differently — tissue oxygen tension probes, transcutaneous oxygen measurement, or near-infrared spectroscopy for regional tissue saturation.
What moves it. The levers that move tissue oxygenation are blood flow, capillary density, haemoglobin level and how readily haemoglobin releases its oxygen. Acidity shifts the oxyhaemoglobin dissociation curve so that oxygen is released more easily — the Bohr effect — and rising temperature shifts it independently in the same direction. Both are real physiology, and a plausible route by which warming affects how oxygen is handed over to tissue.
Why it matters here
"Oxygenation" is used loosely across oxygen and ozone material. This entry is the plain version: it is about blood flow and delivery, and it is not the number on a fingertip oximeter.