All functions of the human organism depend on an adequate supply of oxygen. The oxygen is needed to form energy through oxidation of the nutrient. While under the everyday conditions of life there are enough nutrients in the body, or can be absorbed through food at any time, the oxygen with and from the air is absorbed through the lungs through the respiratory activity. However, an increase in breathing is only possible to a limited extent. In addition, the transport of oxygen in the blood to the cells basically occurs by binding to the red blood pigment hemoglobin. This transport is limited for 2 reasons: on the one hand, by the amount of hemoglobin in the red blood cells and on the other hand, by the amount of oxygen that can be absorbed by one molecule of hemoglobin at a time. In accordance with the vital importance of oxygen, the maximum possible amount of oxygen is transported under normal conditions by the chemical binding of oxygen to the hemoglobin and an increase is not possible. In contrast to other gases, oxygen in the blood fluid, the blood plasma, is poorly physically soluble. However, if the oxygen pressure and thus the oxygen concentration is increased, more oxygen can be transported in the blood. It should also be noted that the transfer of oxygen from the lungs into the blood and from the blood into the cell always takes place in the form of dissolved oxygen, because the hemoglobin is only present in the blood and not outside it. Hyperbaric oxygen application thus improves an important physiological process. Too high a concentration of oxygen can also have various side effects, which is why high oxygen concentrations are only used in certain clinical situations under constant clinical supervision. However, hyperbaric oxygen therapy with 1.5 ATA (0.5 bar) supports the physiological process of absorbing and delivering oxygen from the lungs into the blood and from the blood into the cells and therefore does not cause any undesirable side effects when used properly. Every cell in the organism needs oxygen to function. However, this is especially true for the nerve cells, i.e. the brain, and for the cells of the heart muscles. The brain is the highest control authority of the organism, the heart ensures blood circulation and thus the supply and disposal of the cells. The support of these vital functions is the basis for the use of hyperbaric oxygen therapy in a large number of functional disorders and justifies the large number of health-promoting applications. In our body, 75 trillion cells work to provide energy for the brain and organ functions. For their diverse functions, the cells need nutrients and oxygen, although the nutrients cannot be used for energy production without oxygen.