HYPERBARIC OXYGEN THERAPY
It is a modality which increases the percentage of dissolved oxygen in the blood, thereby increasing oxygen delivery to tissue.
It invloves placing the patient in a hyperbaric chamber and delivering oxygen at high pressure- usually more than 2atmospheres.
There is no technique called Local Hyperbaric Oxygen as that would not increase the percentage of oxygen in the blood, which is the basis of HBOT.
It has been found to be useful in wound healing and especially the diabetic foot where there is reduced circulation. That does not however mean that it is useful or will work in all cases. Like any other modality, the use of HBOT is determined by the circumstances and the need of the wound, the medical condition of the patient among various other factors.
You could compare HBOT to dissolving one spoon of sugar in two cups of tea, one cup is full and the other is half full. Putting the same amount of sugar in both cups will result in the half full cup of tea being sweeter than the one which is full. Similarly because HBOT increases the oxygen content of blood, even if the volume of blood going to a part is low, because of the high concentration of oxygen which can exceed 10-15 times normal, the part gets enough oxygen to help in wound healing.