Abstract
BackgroundCarbon dioxide (CO2) therapy refers to the transcutaneous administration of CO2 for therapeutic purposes. This effect has been explained by an increase in the pressure of O2 in tissues known as the Bohr effect. However, there have been no reports investigating the oxygen dissociation of haemoglobin (Hb) during transcutaneous application of CO2 in vivo. In this study, we investigate whether the Bohr effect is caused by transcutaneous application of CO2 in human living body.MethodsWe used a novel system for transcutaneous application of CO2 using pure CO2 gas, hydrogel, and a plastic adaptor. The validity of the CO2 hydrogel was confirmed in vitro using a measuring device for transcutaneous CO2 absorption using rat skin. Next, we measured the pH change in the human triceps surae muscle during transcutaneous application of CO2 using phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in vivo. In addition, oxy- and deoxy-Hb concentrations were measured with near-infrared spectroscopy in the human arm with occulted blood flow to investigate O2 dissociation from Hb caused by transcutaneous application of CO2.ResultsThe rat skin experiment showed that CO2 hydrogel enhanced CO2 gas permeation through the rat skin. The intracellular pH of the triceps surae muscle decreased significantly 10 min. after transcutaneous application of CO2. The NIRS data show the oxy-Hb concentration decreased significantly 4 min. after CO2 application, and deoxy-Hb concentration increased significantly 2 min. after CO2 application in the CO2-applied group compared to the control group. Oxy-Hb concentration significantly decreased while deoxy-Hb concentration significantly increased after transcutaneous CO2 application.ConclusionsOur novel transcutaneous CO2 application facilitated an O2 dissociation from Hb in the human body, thus providing evidence of the Bohr effect in vivo.
Highlights
Carbon dioxide (CO2) therapy refers to the transcutaneous or subcutaneous administration of CO2 for therapeutic purposes especially in the treatment of peripheral vascular disorder [1]
We investigated whether our transcutaneous CO2 application system caused CO2 absorption into local tissues and the Bohr effect in the human body, by real time and non-invasive measurement of changes in pH and oxygenated and deoxygenated-hemoglobin volume
Four groups of rat skin specimens with or without CO2 hydrogel that had been filled with CO2 gas or air were used in the experiment
Summary
Carbon dioxide (CO2) therapy refers to the transcutaneous or subcutaneous administration of CO2 for therapeutic purposes especially in the treatment of peripheral vascular disorder [1] One example of this is the use of spa therapy that emerged as an important treatment in Europe during the 1800 s and is still in use in many countries today [2]. Some reports showed that the transcutaneous administration of CO2 rich spa gas improves microcirculation and symptoms in patients who have intermittent claudication [8,9] and Raynoud’s phenomenon [10] These therapeutic effects of CO2 are caused by an increase in blood flow and microcirculation assessed by Laser Doppler [10], and an increase of tcPO2 in ischemic tissues, which is explained by the Bohr effect [3,5,8,9,11]. We investigate whether the Bohr effect is caused by transcutaneous application of CO2 in human living body
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