Simultaneous recording of penile diameter and penile arterial pulse during laboratory-based erotic stimulation in normal subjects.

We have assessed erectile responses of normal male subjects to short periods of fantasy and to short erotic films, using simultaneous measurement of penile diameter and penile dorsal arterial pulse amplitude, together with systemic arterial blood pressure, heart rate and skin blood flow. By a variety of criteria, we have satisfied ourselves that penile pulse amplitude reflected local vascular changes in the penis rather than changes in systemic blood pressure, although it is uncertain whether it was primarily determined by the magnitude of arterial flow or that of arterial volume. Penile pulse amplitude usually increased markedly during the stimulation period, and was correlated with penile erection. The temporal relationship between these two parameters was variable. Typically pulse amplitude increase started later than diameter increase but thereafter changed in parallel. In a proportion of responses, however, these two changes were markedly dissociated in time and these responses tended to be slower in reaching their maximum diameter. This variable association suggests that two separate processes involved in erection are being measured. Simultaneous monitoring of penile diameter and penile pulse may therefore provide further information about the basic physiological processes involved in penile erection as well as diagnostic information in patients with erectile dysfunction of uncertain aetiology.