Penile plethysmograph

Penile plethysmography (PPG) or phallometry is measurement of bloodflow to the penis, typically used as a proxy for measurement of sexual arousal. The most commonly reported methods of conducting penile plethysmography involve the measurement of the circumference of the penis with a mercury-in-rubber or electromechanical strain gauge, or the volume of the penis with an airtight cylinder and inflatable cuff at the base of the penis. Corpus cavernosa nerve penile plethysmographs measure changes in response to inter-operative electric stimulation during surgery. The volumetric procedure was invented by Kurt Freund and is considered to be particularly sensitive at low arousal levels. The easier to use circumferential measures are more widely used, however, and more common in studies using erotic film stimuli.