Urethral pressure variations in healthy females during rest and sleep.

Recent studies have shown the occurrence of rhythmic urethral pressure variations (UPV) in the normal female urethra in the awake state. The nature of these variations still needs further elucidation. In this study we investigated the changes in urethral pressure (UP) and in UPV as they occur in healthy females awake and asleep. UPV, intravesical-(IVP) and rectal pressure (RP), together with anal electromyography (EMG) and electroencephalography (EEG) were measured in 10 healthy fertile female volunteers. The registration was done in the awake state, during falling asleep and during sleep. During falling asleep the average urethral pressure as well as the UPV amplitude and frequencies decreased and remained at a lower stable level during sleep. Urethral pressure and its variations seemed to be interrelated since the UPV frequency and amplitude decreased when the average UP decreased. From this study it appears that urethral pressure is influenced by extrinsic factors such as the waking, resting and sleeping states. Although some extrinsic modulation of urethral pressure variations occurs, their persistance in sleep suggests their local nature.