Use of hyperbaric oxygen therapy in small-animal medicine

Hyperbaric oxygen therapy (HBOT) chambers work on the principle that high oxygen concentration, combined with increased air pressure in the chamber, raises plasma-oxygen concentration, allowing oxygen to diffuse into tissues at distances three to four times further than usual to promote healing.

Crucial for the survival of tissue, HBOT provides oxygen for diseased, edematous and poorly vascularized areas.

The therapy is available and used worldwide in human medicine. There are many conditions that various national health-insurance systems authorize as accepted indications for HBOT (Table 1).

Table 1

HBOT methodology, scientific literature and case examples were presented at the June 6-9 ACVIM Forum in Seattle in the neurology CE session (R. Lyman: "Hyperbaric oxygen therapy in small-animal neurology," 2007 ACVIM Forum, Seattle, proceedings. Log onto www.animalemergency.net to read more on these effects).

HBOT reverses tissue hypoxia, reduces edema by vasoconstriction, stimulates neovascularization and reduces reperfusion injury by enhancing the activity of oxygen scavengers. It increases white-blood-cell killing activity, has direct antibacterial effects and, by regulating receptor production and sites, modulates cytokine and metalloproteinase effects to reduce inflammation. (For a more thorough review of the subject, refer to "Textbook of Hyperbaric Medicine," 4th Edition, KK Jain, Hogrefe and Huber, Cambridge, MA 2004.)

Many scientific publications report on the beneficial effects of HBOT for human diseases and animal models. According to recent publications, HBOT reduced severity and improved survival in pancreatitis models in rats. A citation list includes:

• Mas et al., "Hyperbaric oxygen-induced changes in bacterial translocation and acinar ultrastructure in rat acute necrotizing pancreatitis," J Gastroenterol, 2005, Vol. 40 No. 10, 980-98;

• A. Balkan et al., "Pulmonary protective effects of hyperbaric oxygen and N-acetylcysteine treatment in necrotizing pancreatitis," Physiol. Res. 55:13-31, 2006;

• CN. Cuthberson et al., "Hyperbaric oxygen reduces severity and improves survival in acute pancreatitis," abstract from the 36th Annual Meeting of the American Pancreatic Association, Nov. 3-4, 2005;

• Chen et al., "Hyperbaric oxygen therapy attenuates pancreatic microcirculatory derangement and lung edema in acute experimental pancreatitis in rats," Pancreas, 1998 Jul; 17 (1): 44-9;

• M. Yasar et al., "The effect of hyperbaric oxygen treatment on oxidative stress in experimental acute necrotizing pancreatitis," Physiol. Res. 52: 111-116, 2003;

• Isik AT et al., "The effect of combination therapy of hyperbaric oxygen, meropenem and selective nitric oxide synthase inhibitor in experimental acute pancreatitis;" Pancreas, 2004 Jan; 28 (1): 53-7;

• Cuthberson et al., "Potential effects of hyperbaric oxygen therapy in acute pancreatitis," ANZ J. Surg. 2006 Vol. 76, No. 7, 625-630).

Another study showed accelerated neurological recovery with HBOT and improved survival rate in dogs after 15 minutes of complete global cerebral ischemia (Takahashi et al., "Hyperbaric oxygen therapy accelerates neurologic recovery after 15-minute complete global cerebral ischemia in dogs," Crit. Care Med. 1992 Nov; 20(11) 1588-94).

Hyperbaric chambers are commercially available for both human and veterinary patients.

Typically, hyperbaric chambers are supplied by liquid-oxygen tanks and a large-diameter, medical-grade oxygen pipeline to deliver sufficient gas volume at a rapid flow rate.

The patient is examined before a session and its temperature is taken. Elevated body temperature theoretically increases oxygen uptake that may lead to oxygen toxicity.

Metal objects are removed or covered with cotton bandages to prevent spark formation. A static-inhibitor ground line is placed on the leg. Any IV catheter is covered with a cotton wrap.

The desired treatment pressure is normally between 1.5 and 3 atmospheres in a 100-percent oxygen environment. This pressure is increased slowly over a 10- to 15-minute period until the desired treatment pressure is reached. The time under treatment usually ranges from 45 minutes to two hours. Then, a gradual decompression lasting about 15 minutes is performed.

Two to three treatments a day for about five to 10 days are given for most patients. At least four hours should separate each treatment.

Some patients may benefit from follow-up treatments after discharge from the hospital.

(This is the case for humans with multiple sclerosis in the United Kingdom, where 64 centers exist expressly for the treatment of this disease).

The following are some conditions that are treated by HBOT at our hospital as adjunctive therapy:

• spinal-cord trauma

• intervertebral disc disease (prior and following surgery)

• fibrocartilaginous emboli

• head trauma

• global cerebral ischemia

• pancreatitis, de-gloving injuries

• inflammatory nervous-system diseases.

Over the past two years,our doctors and staff have seen clinical improvements of many cases treated by HBOT. It has enhanced our ability to successfully treat many critically ill patients.