title: Variation in invasive and noninvasive measurements of isovolumetric bladder pressure and categorization of obstruction according to bladder volume.
abstract: OBJECTIVE
  We developed a noninvasive test that provides an estimate of isovolumetric bladder pressure by measuring the pressure required to interrupt voiding using controlled inflation of a penile cuff. We noted variation in serial measurements obtained during a single void and, therefore, we determined whether this represents variation in detrusor contraction strength, as predicted in previous studies, or measurement error.
  
  
  METHODS
  A total of 36 symptomatic men underwent simultaneous invasive and noninvasive pressure flow studies. Corresponding values of isovolumetric bladder pressure and cuff interruption pressure were recorded at each flow interruption and grouped according to bladder volume to calculate measurement error and bias at various points during a void. Individual variation in the 2 measurements across a range of normalized bladder volumes was then examined using ANOVA.
  
  
  RESULTS
  Cuff interruption pressure showed a consistent level of accuracy as an estimate of isovolumetric bladder pressure across a range of volumes. There were similar, statistically significant differences in isovolumetric bladder pressure and cuff interruption pressure recorded at specific volume increments with the highest values seen in the mid range and the lowest seen at lower bladder volumes (each p <0.01). When plotting, the maximum recorded value of cuff interruption pressure in each individual on our proposed noninvasive pressure flow nomogram provided the best diagnostic accuracy for obstruction.
  
  
  CONCLUSIONS
  This study shows that cuff interruption pressure varies in the expected manner with bladder volume and provides a consistent estimate of isovolumetric bladder pressure throughout a void. These data provide important guidance for interpreting noninvasive pressure flow studies and classifying obstruction on the proposed nomogram.
authors.affiliation: Department of Urology and Regional Medical Physics Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: C K
authors.initials: CK
authors.lastname: Harding
authors.forename: W
authors.initials: W
authors.lastname: Robson
authors.forename: M J
authors.initials: MJ
authors.lastname: Drinnan
authors.forename: P D
authors.initials: PD
authors.lastname: Ramsden
authors.forename: C
authors.initials: C
authors.lastname: Griffiths
authors.forename: R S
authors.initials: RS
authors.lastname: Pickard
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003950:Diagnostic Techniques, Urological; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011312:Pressure; D001743:Urinary Bladder / Q000503:physiopathology*; D001748:Urinary Bladder Neck Obstruction / Q000145:classification / Q000175:diagnosis / Q000503:physiopathology*; D014554:Urination; D014563:Urodynamics