Hyperbaric oxygen therapy accomplishes its beneficial results by means of the basic respiratory functions of the body. A simple explanation of respiration is as follows: The air we breathe is comprised of oxygen, 20.96%; carbon dioxide, 0.04%; and nitrogen, 79%. Â When air is breathed into the lungs about one- fourth of the oxygen passes into the blood and is replaced in the expired air by an equal amount of carbon dioxide. The expired air contains about the same amount of nitrogen as the inspired air. Thus, nitrogen serves largely as a bulk vehicle for oxygen and carbon dioxide. This process of breathing is referred to as external respiration.
As a person inhales, the air enters the lungs and is drawn into minute microscopic air sacs known as alveoli. The walls of these alveoli are ultrathin and are in immediate contact with the capillary blood vessels. The thin walls of the alveoli and the capillaries are semi-permeable and permit the rapid passage of oxygen and carbon dioxide between the lungs and the blood stream. Under normal circumstances oxygen is transported in the blood only by the hemoglobin in the red blood cells. Oxygen molecules have such an affinity with the hemoglobin in the red blood cells that the hemoglobin is always about 98% saturated with oxygen.
However, a fact of importance in hyperbaric oxygen therapy is that the red blood cells constitute only 45% of the blood volume, and that the colorless plasma transports very little oxygen under normal atmospheric pressure. The transport of oxygen by the blood from the lungs to the tissues is due mainly to the ability of hemoglobin to combine reversibly with oxygen. The exchange of these gases between the blood and other tissues or organs of the body is sometimes referred to as internal respiration.
Finally, the respiratory process also involves the cells of the body which make up the various tissues, and this phase of the process is known as cellular respiration. Respiration is essential for life. All living cells require oxygen to carry out their necessary functions. These functions cease when oxygen is no longer available. The cells of the body produce carbon dioxide as a waste product. Oxygen is required to produce energy in the cells of the body, and in so doing there is a chemical exchange resulting in the production of water, heat, and carbon dioxide. The carbon dioxide is released into the veins to be carried back to the lungs to be exhaled. When you take your next breath, this complex respiratory cycle is started all over again.