What You Should Know About Using HBO In Diabetic Wounds
Last month, Medicare began reimbursing for hyperbaric oxygen (HBO) treatment as an adjunctive therapy for diabetic foot ulcers. After an exhaustive review of the literature, the Centers for Medicare and Medicaid (CMS) concluded that “HBO therapy is clinically effective and, thus, reasonable and necessary in the treatment of certain patients with limb-threatening diabetic wounds of the lower extremity.” According to the CMS, patients must meet each of the following three criteria: • the patient has type I or type II diabetes and has a lower extremity wound that is due to diabetes; • the patient has a wound classified as Wagner grade III or higher; and • the patient has failed an adequate course of standard wound therapy. The policy also requires that patients show no measurable signs of healing with standard therapy for at least 30 days prior to initiation of HBO.1,2 Medicare based this decision on an analysis of two randomized clinical trials, especially the report by Faglia, one combined randomized/non-randomized trial, seven case series, two abstracts and several technology assessments.3 Technology assessments by the BlueCross BlueShield Association, the Medical Services Advisory Committee in Australia, the British Journal of Medicine Clinical Evidence Report and the Agency for Healthcare Research and Quality concluded that HBO significantly reduces wound size when compared with standard wound care alone. They also concluded that HBO supports a higher rate of complete healing and decreased major amputation rates in diabetic wounds.4-7 The American Diabetes Association 1999 Consensus Development Conference on Diabetic Foot Wound Care recommended that, “It is reasonable, however, to use this costly modality to treat severe and limb- or life-threatening wounds that have not responded to other treatments, particularly if ischemia that cannot be corrected by vascular procedures is present.”8 While an exhaustive review of this literature is beyond the scope of this paper, let’s take a closer look at how HBO can enhance healing in diabetic lower extremity wounds and key considerations in proper patient selection. Understanding The Causal Factors Behind Impaired Wound Healing Diabetes mellitus is the classic example of a systemic disease that directly and indirectly impacts wound healing. While peripheral sensory and motor neuropathy predispose to injury and ulceration of the foot, other factors predispose to wound healing complications. Collagen accumulates at a slower rate and breaking strength is diminished in incisional wounds. Both collagen synthesis and vascular ingrowth are decreased. There is also impairment of the phagocytic function of granulocytes and decreased granulocyte chemotaxis. There is atherosclerosis, which may have a more peripheral distribution in diabetics than in non-diabetics, along with increased thickening and decreased permeability of capillary basement membranes. These vascular changes may limit blood flow and compound local tissue hypoxia in foot ulcers. Not surprisingly, diabetic ulceration and impaired wound healing continue to contribute to high rates of lower extremity amputation in spite of recent advances in distal arterial bypass and angioplasty. Pecoraro concluded that periwound cutaneous perfusion is the critical physiological determining factor of diabetic ulcer healing, indicating a 39-fold increased risk of early healing failure when the average periwound TcPO2 is <20mmHg.9 This finding was independent of segmental Doppler arterial blood pressure at the dorsalis pedis artery level, specifically suggesting hypoxia as a primary determining factor in ulcer healing failure. Although revascularization remains the mainstay of increasing distal blood flow and optimizing periwound perfusion in the diabetic foot ulcer patient, limb salvage and amputation reduction has plateaued with revascularization alone. How HBO Can Facilitate Wound Healing HBO consists of a patient breathing 100 percent oxygen while his or her entire body is enclosed in a pressure chamber. The topical application of oxygen is not recognized by the FDA as hyperbaric therapy and is not reimbursed by Medicare. Oxygen is transported two ways in that it is chemically bound to the hemoglobin and physically dissolved in the plasma.