The effect of carbonic anhydrase inhibition on the tcPCO 2

The transcutaneous carbon dioxide pressure, tcPCO 2 measured on the skin surface by a heated PCO 2 electrode, is higher than the arterial PCO 2 at body temperature. This chapter discusses a study to elaborate the effect of carbonic anhydrase inhibition on the tcPCO 2 . Five volunteers were tested. After attaching the tcPCO 2 and tcP with an adhesive ring on the forearm and waiting for a steady state value, the tcPCO 2 was continuously recorded throughout the experiment. The experiment started about 20 min after the fixation taking a blood sample for gas analysis from the hyperemic ear lobe. At the same time, an average oral dose of acetazolamide was given. This dose causes a noticeable effect on the CO 2 exchange. For control purposes a similar experiment was performed without the drug, seven days later. The PaCO 2 of the ear lobe blood remained almost unchanged, probably due to a compensatory hyperventilation. The difference, D, increased from 5 to 10.3 mm Hg. The highest levels were reached between the 30th and 90th min. PaCO 2 , tcPO 2 , and the arterial pH did not change significantly. A distinct increase of urinary excretion began about 30 min after intake of the drug. During the control measurement no significant changes occurred.