INTRODUCTION:

Hyperbaric oxygen (HBO) therapy has been medically available in Québec since 1982. However, it is an "old" technology that originated in the 1920s. Recognized as the treatment of choice for carbon monoxide poisoning and diving-related decompression sickness, HBO therapy is being used more and more as an adjuvant treatment for a certain number of chronic, nonemergency medical conditions. In Québec, until quite recently, hyperbaric medical services were available only at the Hôpital du Sacré-Coeur de Montréal. Given that hyperbaric medicine has evolved worldwide, the Ministère de la Santé et des Services sociaux would like to know if it would be useful to support wider diffusion of this technology in Québec and, if so, what the guidelines should be for this diffusion. The purpose of this Conseil d'évaluation des technologies de la santé (CETS) report is to enlighten the Ministry and the other policymakers concerned as to the decision-making issues regarding this technology.

OBJECTIVES:

CETS's specific objectives in this report are as follows -To describe hyperbaric oxygen therapy and its mechanisms of action; -To systematically review the scientific literature in order to determine which pathologies and in what conditions HBO therapy is effective; -To review the adverse effects and complications of HBO therapy; -To examine the risks associated with operating a hyperbaric chamber and the necessary safety measures relating thereto; -To estimate the potential demand for HBO therapy in Québec and the costs that would be generated in meeting this demand; -To define the guidelines for meeting this potential demand, if applicable. HYPERBARIC OXYGEN THERAPY In hyperbaric oxygen therapy, the patient is placed in a steel, aluminum or polymer chamber in which he or she breathes pure oxygen (100%) at greater than atmospheric pressure (1.5 to 3 ATA1). Chambers can be of the mono- or multiplace type. Through different mechanisms of action, HBO therapy seems to play a role in the revitalization, revascularization and healing of tissues, grafts and organs, in the preservation and regeneration of bone, and in potentiating certain pharmacologic effects. THERAPEUTIC MODALITIES At present, there are no standard protocols for specific medical conditions. The therapeutic procedures vary according to the condition (acute or chronic) and the treatment centre (physicians caring for the patient, etc.). The treatment can be administered on a one- time basis and vary in duration, as is the case with carbon monoxide poisoning, or by way of several daily or twice-daily sessions of predetermined duration (30 to 90 minutes). The pressure at which HBO is administered depends on several factors the medical condition, the patient's characteristics and the centre's practices. EFFICACY OF HBO THERAPY HBO therapy has reportedly been tried out on nearly 130 medical conditions, but very few of them have been the subject of randomized, controlled, prospective trials. Based on an exhaustive review of the available scientific literature and on the opinions of expert organizations, CETS concludes that hyperbaric oxygen therapy is recommended in the following medical conditions Carbon monoxide poisoning, Decompression sickness, Gas embolism, Gas gangrene, Refractory tissue or bony necrosis due to a single microorganism or a mixed population of microorganisms (aerobic or anaerobic), Post-radiation therapy tissue damage osteoradionecrosis and soft-tissue damage, Chronic tissue lesions associated with chronic critical ischemia diabetic foot, chronic leg ulcers, Severe burns which are refractory to treatment and/or which compromise graft take. The treatment of cerebral palsy with HBO is presently a controversial topic worldwide. Until very recently, there were no clinical studies evaluating the beneficial effect of hyperbaric oxygen on the evolution of this condition, which is classified as a cerebral ischemia. However, one randomized, prospective, double-blind, multicentre clinical study was just conducted by Québec researchers and provides the first rigorous data on this application. The results showed an improvement in an equal proportion of children in the experimental group and in the placebo group. Although the investigators conclude that hyperbaric oxygenation has no effect, other possible interpretations are suggested and raise questions about the factors for improvement, all of which points to the need for further research. COMPLICATIONS Middle ear barotrauma heads the list of complications. Pulmonary barotrauma rarely occurs. Impaired visual acuity in the form of myopia or hyperopia secondary to hyperbaric oxygen therapy has been reported, most often in the context of prolonged treatment. These symptoms are generally transient, but studies specifically concerning these complications are few in number. A few experimental studies (involving animals and in specific study conditions) report oxygen toxicity to certain organs, especially the central nervous system. The origin and mechanisms of this toxicity remain poorly elucidated. SAFETY

MEASURES:

HBO is a treatment that requires continual, close monitoring before, during and after adminis-tration. Regardless of the medical condition to be treated, a potential candidate for HBO therapy must meet strict physiological and psychological criteria (even if they have not yet been standardized). Furthermore, this procedure requires a professionally and technically competent environment. The safety measures pertain to the equipment and its maintenance, the conditions for operating a chamber, and training of both the treatment team, the technical team and the patients. CETS believes that all hyperbaric medical centres (private and public) operating in Québec should be subject to, as a minimum, the Canadian Standards Association (CSA) standard for the use of hyperbaric facilities.

CONCLUSIONS:

HBO therapy has reportedly been tried out on nearly 130 medical conditions, but very few of them have been the subject of randomized, controlled, prospective trials. Based on an exhaustive review of the available scientific literature and on the opinions of expert organizations, CETS concludes that hyperbaric oxygen therapy is recommended in the following medical conditions Carbon monoxide poisoning, Decompression sickness, Gas embolism, Gas gangrene, Refractory tissue or bony necrosis due to a single microorganism or a mixed population of microorganisms (aerobic or anaerobic), Post-radiation therapy tissue damage osteoradionecrosis and soft-tissue damage Chronic tissue lesions associated with chronic critical ischemia diabetic foot, chronic leg ulcers, Severe burns which are refractory to treatment and/or which compromise graft take.