Our objective was to determine if obstructed men use Valsalva maneuver during the voiding phase to improve their Qmax.

Men who were investigated at our Urodynamics Section between January 2014 and February 2016 were invited to participated in this prospective trial, informed consent were obtained. The diagnosis of outlet obstruction was made by the ICS Standarization Terminology and for the inclusion in our cohort of study, inclusion and exclusion criterias were used. (inclusion criteria: IPSS >=7 and a Free Qmax <=10 ng/ml,  exclusion criteria: Pdet Qmax<40cmH20). 175 participants accept to participate in the study and 61 men applied for the selected criterias. (n=61). Routinely we perform a free Qmax during uroflowmeter (FQmax) before instrumentation, and then during urodynamics two filling cistometry and also two flow pressures phases in every patient, for this study we used the same procedures but we asked them to perform during the second voiding phase two Valsalva´s Manouvers of at least five seconds each during the same detrusor contraction after the order of micturition. We compare then the Qmax obtained in the first voiding phase with the two Qmax obtained during the Valsalva maneuvers in the second flow pressures phases (called Qmax 1 and Qmax 2). For the confirmation of the nule hypothesis we use the Wilcoxon signed rank test to compared the parameters obtained during the flow pressure phase of the urodynamic studies, this statistic method was preferred to T-test as the population cannot be assumed to be normally distributed.

For both correlation of samples  the p value was 0.000%, rejecting the null hypothesis, so that confirms the difference obtained between the first Qmax , and the subsequent two Qmax under valsalva manouver were not due to chance alone, with a confidence range of 95%.

We can confirm that in our cohort of study obstructed men, with a normal contractile detrusor, do not improve their Qmax during the voiding phase by using the Valsalva maneuver.

This is the first prospective study using urodynamics values that contributes to clarify a significant misleading clinical concept that obstructed male patients use Valsalva´s Maneuver to increase their Qmax during the voiding phase of micturition.

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