In normal conditions, the greater part of oxygen is transported around the body bound to haemoglobin in erythrocytes. The smaller part of oxygen is dissolved in blood plasma. In the hyperbaric chamber the proportion of dissolved oxygen in plasma increases several times. Because this oxygen in plasma is dissolved, it is capable of entering into tissues where erythrocytes cannot enter, and thus ensures adequate supply of oxygen even in cases when the haemoglobin concentration is reduced or erythrocyte function is defective.
Hyperbaric oxygen therapy increases the release of oxygen free radicals, which are highly reactive compounds, and have an important role in defence against pathogenic microbes. It stimulates the release of growth factor and stem cells, which are involved in healing of tissues.