no longer records any variation on the other hand the pressure transducer continues to record the pressure changes thus the invention provides a means to obtain the curve of changes in penile arterial blood flow in particular during an erection this curve can be obtained from two sources the photoplethysmograph 11 during tumescence while icp is low and inferior to a preset pressure and the pressure transducer 6 which records the pulse on top of the pressure these two curves are analyzed and the evaluation of the surface area under the curves obtained provides a means to calculate the arterial blood flow curve from this curve it is also possible to get the curve of changes in venous blood flow it is then necessary to measure icp even for pressures inferior to the preset pressure value using the two curves obtained icp and changes in arterial pressure and classical laws of fluid mechanics changes in venous flow may be calculated and their curve plotted knowledge of changes in venous blood flow provides information which can be directly exploited to assess venous leaks using this method it is also possible to identify pressure plateaus corresponding to tumescence and pressure peaks linked to contraction of the ischiocavernosus muscles using computer systems with analysis of the signal it is then.