Tumescence is the quality or state of being tumescent or swollen. Tumescence usually refers to the normal engorgement with blood (vascular congestion) of the erectile tissues, marking sexual excitation, and possible readiness for sexual activity. The tumescent sexual organ in males is the penis and in females is the clitoris and other parts of the genitalia like the vestibular bulbs. Arteries in the penis dilate to increase blood volume.
Detumescence is the reversal of this process, by which blood leaves the erectile tissue, returning the erectile tissue to the flaccid state. Something that causes an erection is sometimes referred to as a tumefier (tumefyer) or tumescer.
Nocturnal penile tumescence testing
Regularly, men who experience erectile dysfunction are given a nocturnal penile tumescence (NPT) test, usually over a three-day period. Such a test detects the presence of an erection occurring during sleep using either:
- a small portable computer connected to two bands placed around the shaft of the penis which records penile tumescence,
- a band of paper tape with perforations (similar to coil postage stamps) that is fit snugly around the shaft of the penis and will break at the perforations during penile tumescence.
The goal of nocturnal penile tumescence testing is to determine whether a man can experience an erection while sleeping after reporting he is unable to experience an erection while awake. The average man has 3–5 episodes of NPT each night, and each episode lasts 30–60 minutes, although the duration is reduced with advanced age. If a man does obtain an erection while sleeping, but cannot obtain one while awake, a psychological cause or a medication side effect is usually suspected. Otherwise, if a man does not obtain an erection in either state, a physiological cause is usually suspected.
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