Hyperbaric Oxygen Therapy: Mechanisms, Indications, and Dosing
Mechanisms and approved uses
Hyperbaric oxygen therapy (HBOT) delivers a high inspired oxygen partial pressure at increased ambient pressure. It shrinks gas bubbles, hyperoxygenates ischemic tissue, supports neutrophil killing, promotes wound healing, and causes vasoconstriction that reduces edema. Recognized indications include decompression illness, carbon monoxide poisoning, gas gangrene, crush injury, compromised flaps and grafts, delayed radiation injury, problem wounds, osteoradionecrosis, and refractory osteomyelitis. Pressure matters: 100% oxygen at 2.5 ATA produces a much higher arterial PO2 than 100% oxygen at 1 ATA.
Dosing and safety
Typical treatments use 2.0-2.5 ATA for 90-120 minutes with air breaks to limit pulmonary and CNS oxygen toxicity. Untreated pneumothorax is an absolute contraindication. Relative concerns include bleomycin, doxorubicin, disulfiram, pregnancy, uncontrolled seizures, and claustrophobia. Traps include assuming HBOT is a general wound cure, ignoring air breaks, or confusing chamber pressure with oxygen concentration.
Worked example and rule of thumb
For carbon monoxide poisoning, the carboxyhemoglobin half-life falls from several hours on room air to about 90 minutes on normobaric 100% oxygen, and to roughly 20-30 minutes at 2.5-3 ATA. Rule of thumb: prescribe a pressure, duration, and gas composition, not simply oxygen.