Local cerebral PO2, PCO2, and blood flow measurements by mass spectrometry

Partial pressures of intracerebral tissue gases (PO2, PCO2) and local cerebral blood flow (local CBF) were determined simultaneously by means of a single cannula implanted stereotaxically in a given structure. Minute quantities of the gases (O2, CO2, and tracer gas) were withdrawn continuously. After a short period of tracer (He) inhalation, CBF was measured by determination of the clearance rate (T1/2). The measurements of PO2 and PCO2 were continuous and quantitative, whereas the measurements of local CBF were sequential and quantitative. The results obtained for local CBF were compared with those found with two other methods (H2 clearance by polarography, thermoclearance) in the same structure of the same animal.