Therapeutic use of highly concentrated CO ₂ for wound healing: bathing and non-bathing modalities in a systematic review and meta-analysis

Background Wound healing poses a persistent clinical challenge, especially in chronic wounds like diabetic foot ulcers and pressure injuries. Highly concentrated carbon dioxide (CO 2 ) therapy has emerged as a non-invasive approach to promote healing, but its effectiveness remains uncertain. Objective To evaluate the efficacy of highly concentrated CO 2 therapy, via bathing and non-bathing methods, on wound healing outcomes. Methods This systematic review and meta-analysis followed PRISMA guidelines and was registered in PROSPERO (CRD420251035698). Six databases were searched, identifying 10,348 records. Five randomized controlled trials met the inclusion criteria, involving participants with wounds treated using highly concentrated CO 2 through bathing or non-bathing methods. Two reviewers independently extracted data and assessed risk of bias using the Cochrane RoB 2.0 tool. Meta-analyses were conducted with fixed- or random-effects models, and the certainty of evidence was evaluated using the GRADE approach. Results Five trials ( N = 127 wounds/participants) were included. Meta-analysis of two trials indicated that CO 2 therapy increased the likelihood of complete ulcer healing (RR = 5.33; 95% CI [0.23–126.05]; I 2 = 81.3%), though the evidence was very uncertain due to heterogeneity and imprecision. Another meta-analysis of two trials found moderate improvement in microvascular perfusion (SMD = 0.61; 95% CI [0.23–0.99]; I 2 = 0%), rated as low certainty. Individual studies reported improvements in skin temperature, VEGF, TNF-α, and wound area reduction. Conclusion Highly concentrated CO 2 therapy shows promise in enhancing wound healing. However, further large-scale, high-quality trials across diverse settings are needed to validate its clinical applicability.