The impairment of vasodilatory function is common symptom in elderly especially among those who have arteriosclerosis and diabetic merits. In the 19th-century Europe, CO2-enriched water had been used as naturopathy for hypertensions, exclusively. In 1997 Japan, the CO2-enriched water could be adopted as a clinical application, since the device was developed to produce artificial CO2-water easier.   Thereafter, artificial CO2-water had been comparable effect of natural CO2-hot spring water in experimental animal models (Hashimoto, 1999), and the efficacy has been studied in various disease states of human. In the therapy of peripheral arterial disease (PAD), several reports demonstrated the effects for intermittent claudication including the improved hemodynamic status of immersion part (Hartmann et al, 1997).   Based on these findings, we focused on microcirculatory effects of topical application of artificial CO2-enriched water, and studied clinical efficacy in patients with PAD especially critical limb ischemia (CLI). Initially, we showed that immersion of feet in artificial CO2-water (CO2 immersion) increased the blood flow of feet much higher than the plain water even in the patients with CLI, and it improved the limb preservation rate in patients without indication of revascularization (Toriyama et al, 2002). Furthermore, we clarified that CO2 immersion accelerated wound healing after lower extremities bypass surgery in CLI patients with ulcer/gangrene as an adjuvant therapy (Hayashi et al, 2008).   We summarize the clinical studies for artificial CO2-water foot bathing in PAD, and clarify the therapeutic usefulness of CO2 immersion in CLI patients.

The ulcer of the foot induced by arteriosclerotic obstruction (ASO) is poor prognosis that often comes to amputation. In the meantime, the CO₂ warm water is reported with that it has the powerful vasodilator action. In this research, it was made that the effects for the foot ulcer using the high concentration CO₂ warm water bathing was examined to be a purpose.
The subjects are the 49 cases (average 66-years, male: female=20: 29) degree of Fontaine II-IV. We prepared high concentrated CO₂ warm water in approx. 1, 000ppm at 38— technically utilizing an artificial gas-permeable dialysis membrane (MRE-SPA, Mitsubishi Rayon Engineering Co., Ltd.). Using the partial bathing with this CO₂ warm water, the progress was observed on the improvement of foot ulcer in the bathing of 10min. as the period, and of 1-2time/day. In addition, the peripheral tissue bloodflow and the transcutaneous oxygen partial pressure in dorsum pedis during the warm water bathing were observed.
The obvious improvement on each case of ulcer was confirmed within several months. The peripheral tissue blood flow (before bathing 1.1±0.5ml/min/100g) was increased after 1min and it rose to 4.4±1.8 after 10min from the beginning to bathing (p<0.01). Afterwards, it immediately returned to the previous value after the end. In the meantime, though the transcutaneous oxygen partial pressure was 40.7±18.3mmHg prior to the bathing, it increases after 10min with 50.7±18.2mmHg (p<0.05), and it was maintained at 50.3±20.8mmHg in 20min after bathing (p<0.01). And, in each Fontaine groups it significantly increase with the peripheral tissue bloodflow and the transcutaneous oxygen partial pressure.
As a conclusion, the partial bathing of the foot with high concentration CO₂ warm water is effective as the therapy for the foot ulcer caused by ASO. The mechanism indicated that the rise of transcutaneous oxygen partial pressure and peripheral tissue bloodflow was concerned without relating to the seriousness of ASO.