Therapeutic principles of hyperbaric oxygen

1) Physical dissolved oxygen increases
Breathing air under normal pressure, the oxygen in the air diffuses from the alveoli through the membrane barrier of the alveolar and capillary walls, such as blood, most of which are combined with hemoglobin to form oxyhemoglobin, only a part of which is dissolved in blood (dissolved in every 100 ml of blood). Oxygen is only 0.3 ml). According to Henry's Law, the diffusion (physical dissolution) of a gas into a liquid is proportional to the pressure of the gas. The body is under hyperbaric oxygen. Due to the high partial pressure of oxygen, the diffusion of high-pressure oxygen from alveoli to blood and body fluids is mainly physical dissolution. Pure oxygen is absorbed at 2.5~3 atm, and the amount of dissolved oxygen per 100 ml of blood From 0.3 ml of inhaled air under normal pressure to more than 5.6 ml, an increase of nearly 20 times, and the arterial blood oxygen tension rose to 1770 mmHg (235.9 kPa). The physical dissolved oxygen in the body is increased to meet the body's oxygen demand.

The significance of the increase of physical dissolved oxygen under hyperbaric oxygen is to realize the bloodless survival of life. Hemoglobin-bound oxygen dissociates very little or not at all under hyperbaric oxygen. Experiments have confirmed that under hyperbaric oxygen, when the body's hemoglobin is reduced to almost zero, there is still no sign of hypoxia on the electrocardiogram, suggesting that even without hemoglobin under hyperbaric oxygen therapy, the survival of blood-bearing organisms can be temporarily maintained. Moreover, the physical dissolved oxygen is the oxygen that runs in front of the red blood cells, so it has a unique effect on ischemia without a lack of tissue fluid hypoxia.

2) Increased tissue oxygen storage
Oxygen continuously reaches the tissue cells from the blood, and the cells continuously consume oxygen. During this dynamic equilibrium process, the tissue often maintains a certain amount of residual oxygen, which is the oxygen storage capacity of the tissue. Under normal temperature and pressure, the average oxygen storage capacity of 1 kg of tissue is about 13 ml, and the average oxygen consumption per kg of tissue is 3 to 4 ml/min under normal circumstances. According to theoretical calculation, the safe time limit of circulatory blocking is 13÷(3-4)=3~4 minutes. When inhaling pure oxygen at 3 atm, the average oxygen storage per kilogram of tissue increases to 53 ml, and the safe time limit for circulatory interruption can be extended to 8 to 12 minutes.

Experiments have shown that the oxygen consumption of tissue cells is reduced at low temperatures, the safe weaning time is longer, and the tissue oxygen storage is increased. If the body temperature decreases by 5°C, the physical dissolved oxygen in the blood increases by 10%, the oxygen consumption in the heart muscle decreases by 20%, and the oxygen consumption in the brain decreases by nearly 50%. Therefore, hyperbaric oxygen combined with low temperature can further prolong the safe time limit of the circulatory block, thereby creating conditions for cardiac surgery.

3) Increase the diffusion rate and effective diffusion distance of oxygen

The diffusion rate and effective diffusion distance of oxygen, that is, the penetration force of oxygen, depends on the gradient of the oxygen tension between the diffusion zone and the diffused zone. Hyperbaric oxygen can greatly increase the oxygen tension gradient between alveoli and blood, between blood and tissue cells. Due to the large oxygen tension gradient, the diffusion rate of oxygen is fast, and the diffusion rate of oxygen and the effective diffusion distance (that is, the penetrating force of oxygen) is large. Big)