Center for Hyperbaric Medicine: Mechanisms of Action

HBO is used for conditions in which ischemia, edema, bubble formation, or the presence of a toxin interferes with tissue function, survival or repair. The beneficial effects of HBO are achieved through several mechanisms.


  • 10-to-15 fold increase in oxygen dissolved in plasma
  • Two-to-three fold increase in oxygen diffusion distance
  • Elevated tissue PO2s for two to four hours after treatment


  • Alpha adrenergic-like effect
  • 20 percent reduction in blood flow
  • 20 percent reduction in edema

Bubble reduction

  • Volume inversely related to pressure (Boyle’s law)
  • Counterdiffusion: oxygen replaces inert gas in bubble

Antimicrobial effect

  • Facilitation of oxidative WBC killing in ischemic environment
  • Inhibition of toxin formation (gas gangrene)
  • Bacteriostasis (anaerobes)
  • Enhanced antibiotic transport across cell wall (aminoglycosides)


  • Enhanced tissue viability until collaterals develop
  • 20 percent acceleration of capillary formation
  • Angiogenesis (collagen deposition and capillary budding)

Other cellular processes

  • improvement of mitochondrial respiration
  • inhibition of lipid peroxidation
  • impairment of leukocyte adhesion to injured microvasculature