'Perfusion pressure' and 'aortic pressure' are two terms used to describe one of the pressure parameters in a Langendorff Heart experiment.
Described below is a quick guide describing the technique used to measure the perfusion/aortic pressure using a pressure transducer.
Firstly, the perfusate in the perfusate reservoir is typically gassed with 95% O2 and 5% CO2 for at least 30 minutes. The perfusate then flows into the aorta of the heart via a 3-way tap. The catheter of the pressure transducer is also connected to the 3-way tap, which allows constant measurement of the perfusion/aortic pressure.
NOTE: the second transducer (with a balloon catheter) on the right hand side of the diagram is inserted into the left ventricle of the heart to measure left ventricular pressure.