AJP - Heart and Circulatory Physiology, Vol 236, Issue 1 29-H34, Copyright © 1979 by American Physiological Society
Measurement of myocardial PCO2 with a microelectrode: its relation to coronary sinus PCO2
R. B. Case, A. Felix and M. Wachter
A micro-PCO2 electrode, with dimensions of 1 x 10 mm, and a 63% response
time of 14 s was inserted into the left ventricular myocardium of the
pentobarbital-anesthetized dog. Continuous recordings were made of
myocardial PCO2 (PmCO2), arterial PCO2 (PaCO2), and coronary sinus PCO2
(CSPCO2) during variation of respiratory rate. PmCO2 and CSPCO2 were
compared at varying coronary flow. PmCO2 was similar to and closely
followed changes in CSPCO2. The difference between PmCO2 and CSPCO2 was
-0.52 +/- 3.63 (SD) mmHg, and PmCO2 exceeded PaCO2 by 20.69 +/- 5.12 mmHg.
After coronary occlusion, PmCO2, rose promptly, but CSPCO2 was only
slightly elevated until the occlusion was released, when a CO2 efflux into
the coronary sinus occurred. It is concluded that the electrode measures
extracellular PCO2 and that extracellular and myocardial PCO2 are
essentially equal. PmCO2 rises rapidly following coronary occlusion.
