The type of equipment used depends on the study which is performed, the size of the animal, and whether it is under general anaesthesia. For injection of contrast media and measurement of blood gas concentrations, simple sterile polytubing can be used. Measurement of pressures can be performed through fluid filled systems; however, electronic catheter-tip transducers, such as the Millar catheter, are preferable. Dye dilution and thermodilution techniques require two catheters to be placed in the right side of the heart, one in the atrium and the other in the PA. Special balloon-tipped catheters such as a Swan-Ganz catheter are required for measurement of pulmonary wedge pressures. A length of approximately 150 cm is required for a catheter to reach from the cervical jugular vein, through the right side of the heart, to the PA. Pressure monitoring equipment, chart recorders, equipment for blood gas analysis and measurement of dye concentration, cardiac output computers, sensitive thermistors and pressure injectors may be required, depending on the type of study performed.