A penis pump is a cylinder that is fitted over the penis, with a manual or motorized pump to create suction. As the apparatus creates a vacuum around the penis, blood is drawn into the penis, helping it to become engorged. As vacuum increases, the difference between the inner blood-pressure and the pump pressure increases as well; excessive pressure causes vascular damage rather than a harder penis.
A penis pump with a translucent cylinderPenis pumps, usually described in this context as vacuum pumps, have use in conventional treatment of impotence. The pump itself is essentially as described above, although often made to higher standards of quality with a much higher price, and arrangements for distribution by suppliers of medical equipment.
Flexible compression rings, commonly called cock rings, can be added. Fitted on the open end of the cylinder, then an erection is created by pumping. Then the rings are pushed by hand onto the base of the erect penis before releasing the vacuum. This restricts blood flow out of, but not into the penis, enabling the erection to be held even in the presence of problems of the vascular or nervous system which would otherwise lead to immediate loss of erection. In the best circumstances erections can be maintained for a considerable time, but manufacturers' literature recommends that, for safety, rings should be removed after no more than 30 minutes.
Pumping must be done very carefully to avoid injury. Over-enthusiastic pumping can burst blood vessels and form blisters. In some cases the testicles can be unexpectedly pulled into the cylinder and cause severe pain and injury. It is also believed that the rim of the cylinder can cut into the skin and over time cause damage to the ligaments surrounding the penis. Impatiently pumping without reading explanatory material can produce too much suction (any pressure lower than 10 torr/1,333 Pa) and cause permanent injury. Attempts at using vacuum cleaner units for this purpose have resulted in severe injury as the machine produces far too much suction. However, scientists Graham Rutherford and Anne Henke have also undertaken significant research in this area, being funded by some of the major names in sexual pleasure toys, such as Ann Summers. Mild pumping has led to the strengthening of penis muscles and also, for psychosomatic reasons, has led to decreased masturbatory rates in later life.
The effectiveness of penis pumps was examined by Kazem, Hosseini and Alizadeh. They studied 37 men with penis length less than 10 cm and found no significant change in penile length after using pumps for six months, although the follow-up have found 30% satisfaction with the method.