The Tissue Response to Hypoxia: How Therapeutic Carbon Dioxide Moves the Response toward Homeostasis and Away from Instability

Abstract

Sustained tissue hypoxia is associated with many pathophysiological conditions, including chronic inflammation, chronic wounds, slow-healing fractures, microvascular complications of diabetes, and metastatic spread of tumors. This extended deficiency of oxygen (O2) in the tissue sets creates a microenvironment that supports inflammation and initiates cell survival paradigms. Elevating tissue carbon dioxide levels (CO2) pushes the tissue environment toward “thrive mode,” bringing increased blood flow, added O2, reduced inflammation, and enhanced angiogenesis. This review presents the science supporting the clinical benefits observed with the administration of therapeutic CO2. It also presents the current knowledge regarding the cellular and molecular mechanisms responsible for the biological effects of CO2 therapy. The most notable findings of the review include (a) CO2 activates angiogenesis not mediated by hypoxia-inducible factor 1a, (b) CO2 is strongly anti-inflammatory, (c) CO2 inhibits tumor growth and metastasis, and (d) CO2 can stimulate the same pathways as exercise and thereby, acts as a critical mediator in the biological response of skeletal muscle to tissue hypoxia.

Modification of Peripheral Blood Flow and Angiogenesis by CO2 Water-Bath Therapy in Diabetic Skeletal Muscle with or without Ischemia

“…Such beneficial effects of balneotherapy are considered to be due to marked vasodilatory and anti-inflammatory actions of CO 2 . In fact, both clinical and experimental investigations have revealed that CO 2 therapy improves blood flow in the ischemic limb in PAD [4,[19][20][21][22][23][24][25][26][27][28]. Due to the microcirculation promoting effect of CO 2 , angiography using CO 2 has been employed to monitor immediate response to endovascular therapy of PAD [29][30][31][32].…”