In wound healing, remember that an acute wound goes through several stages of healing, beginning with injury. A wound will progress through hemostasis, an inflammatory and proliferative phase, and then maturation. A nonhealing wound will arrest in one of these phases, typically between the inflammatory and proliferative phases. Many phases of wound healing require oxygen, particularly the cross-linking and maturation of collage. Studies by Hunt et al in the late 80’s demonstrated that increasing oxygen tension increases the rate of collage deposition.
At sea level, hemoglobin carries 1.38 ccs of oxygen per gram. One mL of plasma will have about 0.003 mL per mm Hg of the partial pressure of oxygen. Some of you may recall the Fick equation for the calculation of oxygen consumption:
VO2 = (CaO2 – CvO2), or oxygen consumption, equals the difference between the arterial content of oxygen in the blood and venous oxygen content.
On the average, the body extracts 5-6 mLs of oxygen for every 100 mLs of blood circulating, or, an extraction rate of 5-6 volume percent. An Hg level at 6 or below will make oxygen delivery inadequate.
Hyperbaric oxygen therapy can increase the dissolved amount of oxygen about 2 vol % per atmosphere so that at 3 ATA there is enough dissolved oxygen in the plasma to sustain life. This was proven by Ite Boerema who in 1959 performed exchange transfusions on pigs with dextran/dextrose/RL solution to reduce Hg levels to 0.4 – 0.6 g/dL. Although paler than ghosts, the pigs survived at 3 ATA.