Hyperbaric oxygen normalised microvascular reflexes in patients with peripheral arterial disease

BACKGROUND: The abnormal microvascular reflexes seen in vascular patients are of importance in the pathogenesis of complications. We investigated the influence of oxygen on two reflexes, the vasoconstrictive response to leg dependency (VCD) and the vasodilatory response to thermal stimulation (VDT), in diabetic and non-diabetic patients with peripheral arterial disease. METHODS: 19 diabetic (D) and 5 non-diabetic patients (ND) with occlusive arterial disease and 5 normal subjects (N) were recruited for this study. Laser doppler flowmetry and transcutaneous oximetry were measured on the forefoot in supine position and then 3 minutes after leg dependency at 50. The second set of measurements were taken in supine position and then 10 minutes after the laser doppler probe was heated to 44 C. The tests were repeated while giving the patients 100percent oxygen at 2.4 atmospheres of absolute pressure. RESULTS: Mean tissue oxygenation was 48 mmHg in (D) group, 55 mmHg in (ND) group and 66 mmHg in (N) group. Mean VDT was 580percent, 656percent and 1426percent respectively. In contrast, mean VCD was 15percent, -18percent, and 33percent respectively. However, after oxygen administration to the patients, the mean tissue oxygenation improved to 514 mmHg in group (D) and to 839 mmHg in group (ND) (p less than 0.001, Wilcoxon). Moreover, the mean VDT response increased to 1379percent and 1377percent respectively (p= 0.003, Wilcoxon). Furthermore, the mean VCD responses improved to 35percent and 25percent respectively (p=0.010, Wilcoxon). CONCLUSION: Hyperbaric oxygen normalised vasoconstrictive and vasodilatory responses to dependency and to thermal stimulation in diabetic and non-diabetic patients with arterial disease. This suggests an improvement in the endothelial function in both groups of patients and an improvement in autonomic nerve function in the diabetic group of patients. These findings provide further explanation to how ischaemic and diabetic foot ulcers benefit from hyperbaric oxygen therap