## 4 Discussion  
We have earlier described the rationale and design of this study undertaken to evaluate the clinical utility, efficacy and safety of a novel approach involving bathing in CO2-enriched water for the treatment of foot ulcers [37]. Although several different approaches have been undertaken to facilitate healing of foot ulcers, it is clear that such approaches require multidisciplinary management if amputation is to be avoided [38]. Several therapies are available in clinical practice and include topical agents, dressings, engineered tissue, cell therapy, growth factors, devices and herbal/natural remedies [1]. Furthermore, novel therapies such as magnetic fields have been employed and show great potential in promoting wound healing and have already been utilized in the management of diabetic wounds [39]. The potential of polymeric wound dressing has also been evaluated in wound care management [40]. In addition, improvements in hydrogel dressings have enabled advancements for wound healing [41]. With the development of nanotechnology, specifically glass/hydrogel nanoparticles, incorporating bioactive agents or cells, has allowed a prolonged availability of target molecules at the wound site, and thereby facilitating wound healing [41; 42]. Novel therapies including traction force-activated payloads local delivery of short-interfering RNA are also potentially of value in the healing of wounds [42]. The evidence for the beneficial actions of topical oxygen therapy in healing of diabetes-related foot ulcers and the likelihood of healing has recently been examined; however, the effect on amputation and cost-effectiveness of such therapy was unclear [43]. An improved lower limb ulcer healing in response to increase tissue oxygenation via hyperbaric oxygen has been reported [44]. Negative pressure wound therapy (NPWT) is one of the most effective techniques for the treatment of foot wounds. Although some advancements in this technique have been achieved, due to the complex pathogenesis and management of diabetic foot, irregular application of NPWT has been linked to complications, such as infections, bleeding and necrosis that seriously affect its treatment outcomes [45]. Based on the aforementioned information, it is apparent that several different approaches are available for the healing of foot ulcers, however their efficacy is dependent on an adequate arterial perfusion [46]. The present foot care study has generated data on the safety, tolerability, vascular efficacy and capacity to heal ulcerated foot lesions. While no statistically significant differences (\(p<0.05\)) in the group/time interaction effect were observed, there is a clear separation within the wound area reduction/wound area/oxygenated Hb outcomes. The lack of statistical difference at the level of \(p<0.05\) may be attributed to the small sample size. There is likely an acceleration in the process of wound healing in response to foot bathing in carbonated (1000 ppm-1200 ppm) water at 37 \(\pm\) 0.5 \({}^{\circ}\)C. The facilitated wound healing seen in the treatment group may be associated with an increase in O2 saturation and oxygenated hemoglobin levels at site of wound. Interestingly, in some cases, we also observed that foot bathing in carbonated water alleviated ischemic discoloration of skin (_data not shown_). Although ABI was largely not measurable in the placebo (control) group, as well as in some patients in the treatment arm, due to non-compressibility of arteries [47; 48], based on the pre- and post- treatment values of ABI in the CO2 treated group, the accelerated healing of wounds in this group may be associated with an increase in peripheral circulation. However, it should be mentioned that while no significant differences in the serum levels of VEGF were observed between control and CO2 groups, the median VEGF serum concentration was higher in the CO2 treated group following longer duration (2-4 months) of treatment, suggesting the possibility of new collateral blood vessel formation [49].