Hyperbaric oxygen therapy (HBOT) involves the application of oxygen (a gas) under pressure, therefore a short lesson in physics is needed to understand the basic principles.
“Normal” atmospheric pressure that we live under exerts approximately 14.7 pounds per square inch (psi), or 760 millimeters of mercury (mmHg) on our bodies and on the surrounding air that we breathe. This atmospheric air is approximately 79% nitrogen and 21% oxygen, resulting in an oxygen pressure of about 160 mmHg.
HBOT is talked about in terms of atmospheres absolute (ATA). Normal atmospheric pressure at sea level of 14.7 psi or 760 mmHg is equal to 1 ATA. Anyone with scuba diving experience may remember that as you dive you experience an increase in pressure with increasing depth.
Each 33 feet of sea water provides an equivalent increase of 1 ATA of pressure. Therefore, at 33 feet underwater you are at 2 ATA. 2 ATA is equivalent to 14.7 psi gauge pressure on a hyperbaric chamber console as a gauge will NOT register the already present atmospheric pressure of 14.7psi.
Normal circumstances of oxygen delivery in the body are dependent on the following:
Proportion of oxygen in the air that we breathe
The amount of hemoglobin in the blood
The body’s normal circulation processes (blood pressure)
The hemoglobin molecule is the primary carrier of oxygen to the tissues under normal atmospheric circumstances. Hemoglobin is approximately 97% saturated with oxygen and there is a smaller amount of oxygen dissolved in the plasma. Increasing the inspired oxygen alone, cannot improve delivery by hemoglobin, and breathing 100% oxygen at normal atmospheric pressure will only increase the amount of oxygen dissolved in the plasma by a small amount. The amount of oxygen dissolved in the plasma is referred to as the partial pressure of oxygen and is designated as pO2.
The atmosphere and the mitochondria in the cells are part of a complicated transport system along which the pO2 is reduced; this determines the rate at which oxygen can be delivered to the tissues. The succession of diminishing pO2 is called the “Oxygen Cascade”. The oxygen cascade involves a successive decrease in the partial pressure of oxygen as blood flow leaves the lungs and progresses to the cellular level, such that the capillary pO2 is less than 50 mmHg at the capillary level and even lower at the intracellular level.
If you calculate the increase in partial pressure of oxygen obtained in the gas breathed in during HBOT you will see that it is dramatically increased. At 2 ATA with 100% oxygen: 2 x 760 mmHg = 1,520 mmHg of oxygen.
Breathing air (21% oxygen or 160 mmHg per ATA) would result in a pO2 of 320 mmHg. Therein lies the essence of hyperbaric oxygen therapy, the ability to dramatically increase the inspired oxygen and thus the amount of dissolved oxygen in the plasma. Most therapeutic applications of HBOT involve 3 ATA or less.
Known and identified by many names including Veterinary HBOT (Hyperbaric Oxygen Therapy), Veterinary Hyperbarics or even Veterinary Oxygen Therapy in some areas, the results have been nothing short of remarkable.