A certain amount of pressure is required for vaginal penetration. One measure of therapeutic outcome for erectile dysfunction is to measure the penile rigidity while under an axial load. This can be used as an office test for titrating the dose of medication needed to treat erectile dysfunction.
Pressure on Rod (Karacan et al, 1985)
Vaginal Penetration
< 0.5 kg
0% (none)
0.5 - 0.99 kg
some
1.00 kg
most
>= 1.5 kg
100% (all)
Goldstein et al developed a penile buckling test to measure outcome of erectile dysfunction therapy. They used a 1 kilogram axial load since this would allow vaginal penetration under most circumstances.
The buckling device consists of:
(1) a cylinder closed at one end that fits over the glans
(2) with an attached pressure gauge for measuring axial force calibrated in kilograms
Protocol:
(1) The patient is treated with the selected dose of medication.
(2) The buckling test is performed at 10 minute intervals for the first hour, then at 15 minute intervals.
Buckling Test to 1 Kg Axial Load
Interpretation
no penile shaft deformation (remains rigid)
positive
penile shaft deformation (bends)
negative
Consecutive Positive Buckling Tests
Correlates With
>= 3
good outcome (adequate erection for sexual intercourse)
2
fair
1
guarded
0
poor outcome (totally inadequate for sexual intercourse)
The presence of 3 consecutive positive buckling tests during the first hour would indicate an adequate erection for at least 20 minutes.
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