What is Hyperbaric Oxygen Therapy (HBOT)?
HBOT is a treatment, in which a patient breathes 100% oxygen intermittently while inside a treatment chamber at a pressure higher than sea level pressure (i.e., >1 atmosphere absolute; atm abs). It can be viewed as the new application of an old, established technology to help resolve certain recalcitrant, expensive, or otherwise life-threatening medical problems.
When a patient is given 100% oxygen under pressure, haemoglobin is saturated, but the blood can be hyperoxygenated by dissolving oxygen within the plasma which gets to the tissues in greater concentrations. In certain circumstances, it represents the primary treatment modality while in others it is an adjunct to surgical or pharmacologic interventions.
Treatment can be carried out in either a mono or multiplace chamber. The former accommodates a single patient; the entire chamber is pressurized with 100% oxygen, and the patient breathes the ambient chamber oxygen directly. The latter holds two or more people (patients, observers, and/or support personnel); the chamber is pressurized with compressed air while the patients breathe 100% oxygen via masks, head hoods, or endotracheal tubes. Breathing 100% oxygen at 1 atmosphere of pressure or exposing isolated parts of the body to 100% oxygen does not constitute HBOT therapy. The patient must receive the oxygen by inhalation within a pressurized chamber. Current information indicates that pressurization should be to 1.4 atm abs or higher.
How does hyperbaric therapy work?
Hyperbaria – Increased atmospheric pressure as a means of increasing oxygen uptake without an enriched oxygen source.
Hyperoxia – Increased total oxygen content.
Hyperbaria is based on the concept of the relationship of gas pressure and uptake in liquids (blood, plasma and tissues). Henry's Law states that "a gas is dissolved by a liquid in direct proportion to its partial pressure." For example, at sea level, atmospheric pressure is 760 mm Hg, the oxygen concentration is 21% and the body's oxygen content or partial pressure, pO2, in blood and plasma is ~ 40 mm Hg.
Red blood cells have a limitation as to how much oxygen can bind with haemoglobin. The plasma portion of the blood typically has about a 3% oxygen concentration.
By placing someone in a in a 3 psi pressure hyperbaric environment, the increase in atmospheric pressure at sea level goes from 760 mm Hg to 915 mm Hg. This increase in gas pressure, increases the partial pressure of the oxygen gas and thus forces more oxygen to be dissolved in the plasma. This saturation of oxygen in the blood, due to the Hyperbaric Oxygen Treatment or HBOT, allows the extra oxygen to be diffused or transported to the surrounding body tissues. Thus, oxygen transport by plasma is significantly increased under HBOT. At three atmospheres pressure, enough oxygen can be dissolved in the plasma to support the oxygen demands of the body at rest in the absence of haemoglobin.