An apparatus, operation and method for measurement of systemic andor pulmonic blood pressure. The heat sink 28 includes a base 12 having a top 14, a bottom 16, and opposing sides 18 and 20. In order to achieve an exact determination of glucose even with a reduced dialysis period, it is proposed that the starting content of glucose in the perfusate is adapted to the glucose content of the body fluid by means of a control device in accordance with a command variable derived from the measurement signals of the measuring cell. After the brief time, the Q loading circuit is turned off and the regenerative amplifier goes into oscillation again. Dynamics in a user’s preferences for items may be attributed to the dynamics in these item states.