Men typically have three to five erections while sleeping. The Nocturnal penile tumescence (NPT) is an overnight test to determine whether these erections are occurring.
If you do not have erections while you sleep, the doctor will look for a health condition or medication that decreases blood flow to the penis or interferes with nerve signals that enable arousal and erection. If you experience erections in your sleep or upon awakening, your erectile dysfunction (ED) may be caused by stress or depression.
The NPT test is done two ways: the strain gauge method and the snap gauge method. The strain gauge method documents changes in circumference when elastic bands on the base and tip of the penis stretch during an erection. The snap gauge method measures erectile function with pressure-sensitive bands that break an erection occurs.
Whatever the cause of your ED, your doctor can recommend treatment that will help.