John J Bauer, MD, FACS John J. Bauer, M.D.

Urology Services, Inc.
G-1121 West Hill Rd.
Flint, Michigan 48507
Tel: 810.232.8888
Fax: 810.232.9190

Nocturnal Penile Tumescence (NPT) Testing

NPT is a procedure that is used to predict the cause of your erectile dysfunction. It allows the urologist to determine and document if you have a true physiologic erectile dysfunction and can help in determining the type of erectile dysfunction as an inflow, outflow or mixed defect. Erectile dysfunction has many etiologies, some respond well to the vasodilator drugs initially or for the rest of your life. Some diseases such as arteriosclerosis (associated with heart disease), high blood pressure, and diabetes exert their effects on blood vessels throughout the body, the penis included.

If your disease causes an inflow erectile dysfunction, over time or when you present to our office for the first evaluation, the vasodilator drugs may not be able to dilate the arteries feeding the erectile bodies. It would be wasteful and an inconvenience to you to try all these therapies if this study could predict their failure up front. Medicare and other insurance carriers require this study before expensive treatments for erectile dysfunction are started, especially the penile prosthetics.

If you have a severe outflow erectile dysfunction, then any therapy that causes an increased inflow during erection may not be adequate for maintaining erections hard enough and/or long enough for satisfactory intercourse. Depending on the severity these outflow problems may only be adequate treated with penile prosthetics.

The system is composed of two parts: (1) an ambulatory nocturnal penile tumescence and rigidity data-logging unit, and (2) a microcomputer with printer for processing and printing the data. The ambulatory unit has a loop transducer which self adjusts in length to track penile circumference. In the presence of tumescence (erection), the loop modestly tightens around the shaft to measure penile rigidity by radial loading. The loop accommodates a size from 5-15 cm diameter. Patients tolerate the procedure without difficulty.

Operation of the Ambulatory Unit:

  1. The unit is strapped snugly to the patient?s inner thigh, and the penile loop is comfortably fitted at the mid-shaft of the penis. A baseline circumference measurement is performed.
  2. The circumference of the penis is measured every fifteen seconds throughout the sleep cycle and the value stored in memory
  3. Rigidity is checked every 3-minutes by energizing the torque motor, and the value is stored in memory.
  4. If the circumference increased more than 3mm, the rigidity sampling rate was increased to once every 30 seconds and those values stored.
  5. When the circumference change falls below 3 mm during detumescence (erection goes away, rigidity checks were again decreased to once every 3-minutes.

The unit is then brought back to the office and hooked to the computer where the data is graphically displayed for rigidity and tumescence. Your doctor will then see you in a follow-up visit to discuss the results and give recommendation regarding the appropriate therapy.

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