Abstract: Catheters are disclosed which are adapted for insertion into the heart and which include at least one inlet opening at the front end thereof, at least one outlet opening at the other end thereof, and at least one intermediate opening therebetween, and which include a cylindrical sleeve for opening and closing the intermediate opening so that it can be selectively opened and closed thereby. These catheters are employed most particularly for the withdrawal of blood from both the inferior vena cava and from the right auricle and/or from the superior vena cava of the heart.

Abstract: A device is disclosed for measuring the concentration of a component of a complex medium, including a dialyzer for separating at least a portion of the component into the dialysate from the complex medium, means for measuring the concentration of the component in the dialyzate, and valve means having a measurement position and calibration position for alternatingly directing the complex medium and a calibration solution, respectively, to the dialyzer so that a calibration of the measuring means can be achieved at intervals between measurements, with the dialyzer being in fluid communication with the measuring means so that the dialyzate from the dialyzer is directed to the measuring means for measuring the concentration of the component in the dialyzate. The device also preferably includes an enzyme reactor.

Abstract: An apparatus is disclosed for measuring the pressure of a fluid comprising a pressure sensing element and a pressure transmitting element. The pressure transmitting element has at least one inlet for receiving the fluid whose pressure is to be measured and a pressure transmitting wall member in fluid communication with the inlet, whereby the pressure transmitting wall member may be brought into contact with the pressure sensing element and a source of vacuum for drawing the pressure transmitting wall member against the pressure sensing element so that the pressure sensing element can substantially measure the absolute pressure of the fluid.