A Jehovah's Witness patient bled massively per rectum, but refused blood transfusion. A bleeding gastric leiomyoma was excised at eventual operation. His hemoglobin value fell to 2.2 gm/100 cc and on the third postoperative day he showed evidence of severe cerebral and myocardial ischemia and congestive heart failure developed. Hyperbaric oxygen therapy caused a reversal of all signs and symptoms of hypoxia, and the patient recovered. Blood taken from a subject breathing air at 1 atmosphere pressure has 0.3 vol% of oxygen dissolved in plasma; if the subject breathes 100% oxygen at 2 atmospheres absolute pressure, the amount of oxygen in physical solution in plasma is 4 vol%. In a patient with greatly diminished hemoglobin value, this increase in plasma oxygen may be adequate to sustain life.
Amonic RS, Cockett ATK, Lorhan PH, Thompson JC. Hyperbaric Oxygen Therapy in Chronic Hemorrhagic Shock. JAMA. 1969;208(11):2051–2054. doi:10.1001/jama.1969.03160110023005