Penile Plethysmograph

Penile Plethysmograph

Penile plethysmography (PPG), or "phallometry", refers to measurement of bloodflow to the penis. 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 circumferencial measures are more widely used, however, and more common in studies using erotic film stimuli.

For sexual offenders it is typically used to determine the level of sexual arousal as the subject is exposed to sexually suggestive content, such as pictures, movies or audio. Although there are individuals who have claimed that phallometry is not always appropriate for the evaluation of sexual preferences or treatment effects, large-scale meta-analytic review of the scientific reports demonstrated that phallometric response to stimuli depicting children is the single most accurate (with only 32% accuracy) method of identifying which sexual offenders will go on to commit new sexual crimes.

For prostatectomy nerve-sparing surgery, the surgeon applies a mild electrical stimulation near the cavernous nerves of penis to verify their locations and avoid operative trauma. Damage to these difficult to see nerves can cause erectile dysfunction outcomes. At the surgery's conclusion, the electrical stimulation penile plethysmograph result is a prognostic which helps to manage the erectile function outcomes earlier than the many months required for recovery.