Does Hyperbaric Oxygen Therapy Facilitate Wound Healing?

Hyperbaric oxygen therapy (HBOT) involves placing the patient in a 100% oxygen chamber at elevated atmospheric pressure levels to increase dissolved oxygen levels in the bloodstream. While HBOT reportedly has antibacterial effects, increases angiogenesis, and reduces edema, potential adverse effects include seizures, barotrauma, and confinement anxiety.

Researchers at the University of Tennessee College of Veterinary Medicine recently conducted a prospective study evaluating use of HBOT for healing of uncomplicated incisional and open wounds in dogs.

Study Design

Under heavy sedation, apparently healthy adult beagles received surgical wounds on the trunk, consisting of 2 full-thickness dermal wounds measuring 2x2 cm that were left open and 2 full-thickness skin incisions measuring 3 cm that were sutured closed. Wounds were then bandaged and dogs wore Elizabethan collars for the duration of the study. Dogs received postoperative hydromorphone and carprofen, as well as trazodone to reduce anxiety during HBOT sessions.

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Dogs were randomly assigned to the HBOT and control groups. On days 1 through 7 after wound creation, those in the HBOT group received 1 treatment per day in a commercially available, veterinary-specific hyperbaric oxygen chamber. Treatment on day 1 consisted of 1.7 atmospheres absolute (ATA) for 30 minutes. Treatment on days 2 through 7 consisted of 2 ATA for 40 minutes per day, plus 10- to 15-minute pressurizing and decompressing periods before and after treatment. Dogs were monitored closely during treatment for any adverse effects.

Open and incisional wound healing was evaluated subjectively during bandage changes throughout the 24-day study. Two blinded observers independently noted wound characteristics, and 1 observer also measured wound size, epithelialization, and wound contraction from photographs.

Histology was performed initially on excised tissue and then on 6-mm biopsies obtained throughout the study. A blinded, board-certified pathologist determined scores for inflammation, tissue repair, inflammatory infiltrate, neovascularization, and collagen formation. Aerobic and anaerobic bacterial and fungal cultures were performed on tissues biopsied on day 7.

Results

The HBOT and control groups each included 1 intact female, 2 neutered males, and 2 intact males with similar mean body weights and sizes. Dogs in the treatment group tolerated HBOT well and had no adverse effects.

The researchers determined that wound healing rates were similar between the 2 groups, regardless of whether dogs received HBOT therapy. The following parameters were comparable between the treatment and control groups:

• Open wound size throughout the study
• Rates of epithelialization and wound contraction
• Histologic scores for inflammation and tissue repair

All incisions healed completely by day 14, and half of all open wounds were epithelialized completely by day 24. Bacterial cultures in both groups were all positive for Staphylococcus and/or Streptococcus spp, but none of the dogs displayed clinical signs of bacterial infection.

Take-home Message

The addition of HBOT to routine management of open and incisional wounds did not provide any perceived benefits; however, the authors suggested that results might be more significant for complicated, infected, or ischemic wounds.