Effects of Hyperbaric Medicine on Infectious Disease

General Mechanisms of Action of Oxygen in Infections:

With disease, oxygen delivery is compromised. The inflammatory response following infection is characterized by capillary leak and vasogenic edema that increases the diffusion distance between the vascular supply of dissolved and bound oxygen and adjacent tissues. Tissue edema also leads to variable degrees of tamponade and venous thrombosis, further compromising perfusion and oxygen delivery. Infection leads to microcirculatory shunting (reducing oxygen extraction) and mitochondrial uncoupling. 

Abscesses and infarcted tissues are avascular spaces that show steep oxygen gradients where pO2s may reach 0 mmHg. Both NO and H2S are elaborated by pyogenic bacteria under stress, acting as alternative electron transport chains and as antioxidants that counter the effects of many antimicrobials we administer. NO and H2S produced by bacteria inhibit mitochondrial respiration in surrounding tissues and the phagocytic oxidative burst, predominantly in monocytes and macrophages using oxidative phosphorylation rather than neutrophils using glycolysis.

Increasing oxygen concentrations in infected tissues is generally beneficial during infection, compensating for reduced vascular perfusion, shunting, and increased oxygen diffusion distances. Hyperoxia and HBO also raise oxygen tensions in hypoxic tissues to levels that optimize killing of bacteria by neutrophils and monocytes. While phagocytosis remains unaffected by low oxygen tensions, killing of microorganisms by the oxidative burst is dependent on oxygen tensions.  In an animal model of osteomyelitis, HBO was as effective as cephalothin therapy. The benefit of HBO in osteomyelitis was postulated to result from decreased edema and restoration of the oxidative burst following improved oxygen tensions.

Continue this topic with Wound Care Education Partners blog: The Use of Drugs Under Pressure 

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Source Reference: Excerpted from Hyperbaric Medicine Practice, 5th Edition with permission from the publisher. Reference Chapter 17,Effects of Hyperbaric Medicine on Infectious Diseases: Basic Mechanisms, by Rodney E. Willoughby, Jr.,

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