NHLBI Workshop Summary Hyperbaric Oxygenation Therapy1.2
15
Background and Rationale
Hyperbaric oxygenation (HBO) therapy is a therapeutic modality of increasing popularity (figure 1) whose rationale is simple: a great many diseases or syndromes haveas a major component a cellular O 2 insufficiency,usually locally,but in some settings globally. Recovery from such conditions would reasonably be expected to be facilitated if cellular access to O 2 could be improved, and HBO represents a technically well-developed approach designed to enhance O2 supply (1). As with any other therapeutic approach, there are potential benefits and risks. (1) HBO should increase tissue Po 2 , but reactive O2 species will be generated, with potential cellular toxicity. (2) Tissue O2 delivery should be enhanced by increased arterial O 2 and capillary Po2 , but hyperoxicvasoconstriction may reduce blood flow and thus tissue delivery of inflammatory cells, nutrient delivery, and metabolite clearance. (3) Growth of certain bacteria is inhibited by high concentrations of O2 ; that of others might be enhanced. (4) Technically, to provide O2 at 2 to 3 atmospheres of pressure is straightforward. However, the potential for mechanical accidents, O 2 toxicity, and thus morbidity exists. (5) Is HBO effective? Current annual estimates of the dollar cost of HBO as used in the United States today exceed $30 million, based on 10,000patients undergoing an average of 20 treatments, each costing $150 (Maryland Institute for Emergency Medical Services System, Hyperbaric Chamber Registry). However, in both acute and chronic illnesses theoretically suited to HBO therapy (e.g., decompression sickness, poorly healing wounds, and chronic infections), a successful outcome could result in overall cost savings as a result of a shorter recovery time and a lower cost relative to other non-HBO therapeutic approaches. (6) Ethical and other considerations. In the past decade there has been a marked resurgence in the number of pa1414
11;
12
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Fig. 1. Patients treated with HBO. showing a rapid increase in the number of patients treatedannually (Maryland lnstitute for EmergencyMedicalServices System, Hyperbaric ChamberRegistry).
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15
Background and Rationale
Hyperbaric oxygenation (HBO) therapy is a therapeutic modality of increasing popularity (figure 1) whose rationale is simple: a great many diseases or syndromes haveas a major component a cellular O 2 insufficiency,usually locally,but in some settings globally. Recovery from such conditions would reasonably be expected to be facilitated if cellular access to O 2 could be improved, and HBO represents a technically well-developed approach designed to enhance O2 supply (1). As with any other therapeutic approach, there are potential benefits and risks. (1) HBO should increase tissue Po 2 , but reactive O2 species will be generated, with potential cellular toxicity. (2) Tissue O2 delivery should be enhanced by increased arterial O 2 and capillary Po2 , but hyperoxicvasoconstriction may reduce blood flow and thus tissue delivery of inflammatory cells, nutrient delivery, and metabolite clearance. (3) Growth of certain bacteria is inhibited by high concentrations of O2 ; that of others might be enhanced. (4) Technically, to provide O2 at 2 to 3 atmospheres of pressure is straightforward. However, the potential for mechanical accidents, O 2 toxicity, and thus morbidity exists. (5) Is HBO effective? Current annual estimates of the dollar cost of HBO as used in the United States today exceed $30 million, based on 10,000patients undergoing an average of 20 treatments, each costing $150 (Maryland Institute for Emergency Medical Services System, Hyperbaric Chamber Registry). However, in both acute and chronic illnesses theoretically suited to HBO therapy (e.g., decompression sickness, poorly healing wounds, and chronic infections), a successful outcome could result in overall cost savings as a result of a shorter recovery time and a lower cost relative to other non-HBO therapeutic approaches. (6) Ethical and other considerations. In the past decade there has been a marked resurgence in the number of pa1414
11;
12
;lEe;; ~"U
'" c c.gj
9
Fig. 1. Patients treated with HBO. showing a rapid increase in the number of patients treatedannually (Maryland lnstitute for EmergencyMedicalServices System, Hyperbaric ChamberRegistry).
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