The next time you suffer an injury, should you breathe in pure oxygen to hasten the healing process? That's what some sports scientists are recommending, as the inhalation of oxygen under high pressure (also called hyperbaric oxygen therapy or HOT) becomes an increasingly popular form of treatment for hurting athletes. Anecdotally, hyperbaric oxygen therapy seems to really be hot: several English football teams have used the technique to successfully treat injured players; in one case, an athlete with ligament damage reduced recovery time by 33% with hyperbaric oxygen therapy therapy, and a second player receiving hyperbaric oxygen therapy recovered in only four days, even though doctors had predicted a three-week lay-off ('Are Hyperbaric Treatments Good for Running Injuries?' Running Research News, vol. 10(2), pp. 12-13, 1994). In the United States, numerous professional athletic teams, including ice hockey (NHL), football (NFL), basketball (NBA) and soccer (MLS), utilise and rely on the use of hyperbaric oxygen as adjuvant therapy for numerous sports-related injuries acquired from playing competitive sports.
These are anecdotal reports, to be sure, but there are decent physiological explanations for hyperbaric oxygen therapy's supposed benefits. First of all, hyperbaric oxygen therapy boosts white blood cell activity in damaged parts of the body, which should help control infections. hyperbaric oxygen therapy also tends to constrict blood vessels and decrease the amount of blood pumped by the heart. Although this sounds like a negative effect, it may actually diminish blood flow to an injured region, helping to reduce pressure and swelling. Naturally, hyperbaric oxygen therapy proponents also claim that hyperbaric therapy increases oxygen supplies to injured areas, which might boost oxidative metabolism and protein synthesis.
Blunting the magnitude of the injury
hyperbaric oxygen therapy appears to be safe, although individuals who are febrile, suffer from upper respiratory infections, or have suffered a trauma to the chest where a pneumothorax is suspected or have a predisposition to tension pneumothorax should not be given the therapy. The potential benefits for sports injuries appear to be a blunting of the magnitude of initial injury, possibly by controlling the neutrophil (white-blood-cell) adhesion as well as an enhancement of healing processes requiring oxygen-stimulated collagen formation and phagocytosis ('Hyperbaric Oxygen Chambers and the Treatment of Sports Injuries,' Sports Medicine, vol. 22(4), pp. 219-227, 1996).
Over the past 20 years or so, hyperbaric oxygen therapy has been used fairly successfully to treat a wide variety of medical conditions, including gangrene, carbon-monoxide poisoning, and the decompression sickness sometimes experienced by deep-sea divers. HOT has occasionally worked well for patients whose tissues have been damaged by radiation, and there's some indication that hyperbaric oxygen therapy could be a useful treatment for bone infections, cyanide poisoning, smoke inhalation, recurrent infections, burns, and traumatic 'crush injuries' in which body parts are mechanically squashed as a result of a motor accident or a hard physical blow to the body.
However, solid scientific research concerning the effectiveness of hyperbaric therapy, much of it carried out in the former Soviet Union, has yielded somewhat mixed results. Overall, the studies suggest that after radiation treatments for malignant cancer, hyperbaric oxygen therapy can enhance tendon and ligament repair in damaged parts of the body.
HOT has also helped to lessen the impact of some spinal-cord injuries and spinal-cord ischaemia in experimental animals, especially when the oxygen was given within two hours of a trauma-producing event. In one study carried out at the Department of Anaesthesiology at the Tohoku University School of Medicine in Japan, blood flow to the spinal cords of 18 laboratory rabbits was shut down for 15 minutes. One group of rabbits then received one hour of hyperbaric oxygen therapy at three atmospheres absolute 30 minutes after reperfusion of the spinal cord, another group received hyperbaric oxygen therapy six hours after reperfusion, and a third assemblage of rabbits was given no oxygen therapy. Neurological functions were then observed for 14 days (Critical Care Medicine, vol. 29(4), pp. 814-818, 2001).
As it turned out, rabbits given hyperbaric oxygen therapy within 30 minutes after the ischaemic insult were able to stand and move around without problems, while those whose oxygen was delayed by six hours and the animals without oxygen showed irreversible paraplegia. The density of spinal motor neurons in ventral grey matter in these latter animals decreased significantly, compared to the hyperbaric oxygen therapy rabbits.
Hyperbaric therapy has also promoted the healing of gunshot wounds and boosted recovery in patients after nervous-system surgery. One study found that hyperbaric oxygen therapy initially limited pressure and swelling inside the brain after a traumatic head injury, although the effect was not long-lasting and pressure eventually rebounded to abnormally high levels.
Does it quicken recovery from sports injury?
Overall, hyperbaric oxygen therapy does seem to limit bleeding and swelling following traumatic injury. However, many athletic injuries are of the 'overuse' type and thus bear little resemblance to the more major catastrophes for which hyperbaric therapy has usually been utilised. To date, not a single published study has linked hyperbaric oxygen therapy with quicker recovery from injury in endurance athletes. The only thing close is an investigation in which hyperbaric oxygen therapy controlled the tissue damage associated with 'compartment syndrome' (Running Research News, op cit). Compartments are simply sections of the leg which are enclosed by tough, connective-tissue wrappers, and compartment syndrome is a condition in which fluid pressure rises to abnormal levels inside one of the compartments, sometimes producing nerve and muscle damage. It's a fairly uncommon affliction, but it does affect some athletes. Unfortunately, this study was carried out with dogs, so it's not certain that hyperbaric oxygen therapy can effectively treat compartment syndrome in humans.
Perhaps the athletes who will benefit most from hyperbaric oxygen therapy are divers, with whom hyperbaric oxygen therapy has been used to treat decompression illness ('Initial table treatment of decompression sickness and arterial gas
embolism, Aviat Space Environ Med, vol. 61(8), pp. 738-43, 1990). However, note that there is a potential down side to hyperbaric oxygen therapy; the increased tissue-oxygen levels associated with hyperbaric therapy may actually increase free-radical damage to muscle-cell membranes throughout the body (free radicals are chemicals which react destructively with the outer wrappers of cells; free-radical concentrations increase as oxygen levels rise).
So what's the provisional verdict on hyperbaric oxygen therapy? To date, very little has been published in peer-reviewed scientific journals concerning the effects of hyperbaric oxygen therapy on sports injuries. Unfortunately, the majority of clinical studies examining the efficacy of hyperbaric oxygen therapy in treating soft-tissue injuries have been limited in their sample size and study design. Further research needs to be conducted suggesting and validating the significant effects of this treatment modality and further grounding its importance in sports medicine ('The Role of Hyperbaric Oxygen Therapy in Sports Medicine,' Sports Medicine, vol. 30(6), pp. 395-403, 2000). In other words, although hyperbaric oxygen therapy is very promising, it's still too early to say whether hyperbaric therapy will one day be as popular as good-old aspirin and ice.