Effect of Dry Carbonic Acid Baths on Blood Rheological Parameters in Patients with Venous Leg Ulcers

<b>Background</b>: Chronic venous insufficiency (CVI) is one of the main causes of venous leg ulcers. Rheological disorders of the blood, such as changes in viscosity, hematocrit, and erythrocyte aggregation and deformability, can impair microcirculation and impede healing. Carbonic acid (CO₂) dry baths are a non-invasive physical method that can affect microcirculation and blood parameters, and this study aimed to assess their effectiveness in ulcer healing and in modifying selected blood rheological parameters in patients with CVI. <b>Methods</b>: This prospective, controlled study enrolled 23 participants (11 patients with active venous leg ulcers and 12 healthy controls). The intervention group underwent ten sessions of dry CO₂ baths, performed twice weekly for 5 weeks. No randomization was applied. Ulcer healing was assessed planimetrically, and blood rheological parameters (hematocrit, blood and plasma viscosity, erythrocyte deformability index [EI], aggregation index [AI], aggregation amplitude [AMP], and half-time of aggregation [T_1/2]) were measured before and after therapy. <b>Results</b>: Following the intervention, the ulcer area decreased significantly (median 3.35 cm² to 1.74 cm²; <i>p</i> < 0.01), as did ulcer circumference (7.33 cm to 5.87 cm; <i>p</i> < 0.01). Hematocrit increased (median 40.25% to 41.50%; <i>p</i> < 0.05), and blood viscosity values at low shear rates approached those of the control group. In contrast, erythrocyte deformability (EI) and aggregation indices (AI, AMP, T_1/2) showed no statistically significant intragroup changes, although intergroup differences persisted. Pain intensity decreased significantly (VAS 6.0 to 3.5 cm; <i>p</i> < 0.05). <b>Conclusions</b>: CO₂ dry baths support the treatment of venous ulcers by improving microcirculation and reducing pain. Their impact on blood rheology may have clinical significance, especially as an adjunct to therapy in chronic venous insufficiency. However, the relatively small sample size (<i>n</i> = 23) should be considered a limitation when interpreting these findings.