Tissues in the human body receive oxygen from the lungs via pathways of capillaries that branch out from arteries throughout the body. These capillaries deliver oxygen to the blood, which carries that oxygen as well as nutrients to different parts of the body. In exchange, capillaries retrieve carbon dioxide and waste gases from the tissues and deliver them through the blood being pumped back to the lungs through the veins to be expelled when a person breathes out. As the tissues absorb oxygen from the red blood cells, this oxygen diffuses to the cellular level, energizing cells with life-giving oxygen. If tissue oxygenation is not sufficient, the cells in the organs, muscles, and other body parts can die off, causing life-threatening illness.
The body’s need for differing levels of tissue oxygenation is related to several factors. When the body is healthy and in a relaxed state, the percentage of oxygen needed in the tissues may be approximately 25%. Athletes and workers, while straining their bones and sinews in challenging tasks with tremendous exertion, can experience an elevated need for oxygen levels of close to 75%. Other factors that affect the need for higher than usual oxygen consumption might include body heat resulting from fever or hot climates, as more oxygen is needed with each degree of temperature rise. On the opposite end of the spectrum, shivering in cold temperatures uses up oxygen quickly, requiring more frequent replenishment. Additionally, any inflammations throughout the body increase the body’s need for elevated tissue oxygenation to counteract unusual body heat.
If the body's tissues are not constantly exchanging oxygen and waste gases, functions cease to operate normally. Wounds may be radically slower to heal, and infections can set in that kill off cells and tissues, effecting organs, and circulation to the limbs. Brain cells without enough oxygen die off within minutes, yet smooth muscles in the bladder can go days without sufficient oxygen. If cardiac output interferes with oxygen transport to organ tissues and throughout the circulatory system due to reductions in blood flow, immediate medical attention, including drugs and oxygen therapy, are required. Mini-embolisms in capillaries that block blood flow, or large clots in arteries, can also leave tissue oxygenation at critically low levels.
The most immediate therapeutic goals for patients with inadequate tissue oxygenation are restoring and maintaining blood flows to vital and most sensitive organs. Certain drugs can improve circulatory flow in certain regions of the body, and sometimes surgeries to remove clots are performed when there is not enough time to save organs or limbs without them. Medical professionals might also use ventilators to ensure the body gets enough oxygen until patients are sufficiently healthy to breathe in enough oxygen on their own.
