title: Does Size Matter? Measured and Modeled Effects of Suprapubic Catheter Size on Urinary Flow.
abstract: OBJECTIVE
  To quantify the effects of catheter size and urinary sediment on catheter drainage, and to determine the French size at which catheter upsizing yields a diminished marginal return in flow.
  
  
  METHODS
  Latex Foley catheters (12-26 French [Fr]) were connected to a simulated bladder. Passive drainage times of 450 mL water were measured over 5 successive trials for each catheter size. The effect of sediment was modeled by adding 2g of infant rice cereal to the water. Measurements were repeated in half-length catheters to assess the effect of catheter length. A computational model of resistance was compared to measured data. Percent differences in catheter resistance based on measured catheter dimensions were determined.
  
  
  RESULTS
  Catheter resistance significantly decreased (P < .001) with increasing catheter size. All catheter sizes had significantly faster (P < .001) drainage times after being shortened, except for the 16 Fr catheter. All catheter sizes exhibited significantly prolonged (P < .001) drainage times after the addition of sediment, except for the 16 Fr catheter. Beyond 18 Fr, larger catheter sizes provided diminishing marginal returns in flow; upsizing from 18 Fr to 20 Fr reduced measured resistance by 19%, which was the lowest improvement in resistance between 2 catheter sizes. The coefficient of determination (R2) between measured and modeled resistances was 0.9754, confirming that the model of catheter performance was accurate.
  
  
  CONCLUSIONS
  Marginal improvement in urine flow occurs with catheter upsizing after 18 Fr; however, shortening catheter lengths may serve as another means of improving flow.
authors.affiliation: Lerner College of Medicine, Education Institute, Cleveland Clinic, Cleveland, OH.
authors.forename: Calvin
authors.initials: C
authors.lastname: Lee
authors.affiliation: Lerner College of Medicine, Education Institute, Cleveland Clinic, Cleveland, OH; Department of Urology, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH; Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH. Electronic address: GillB@ccf.org.
authors.forename: Bradley C
authors.initials: BC
authors.lastname: Gill
authors.affiliation: Lerner College of Medicine, Education Institute, Cleveland Clinic, Cleveland, OH; Department of Urology, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH.
authors.forename: Sandip P
authors.initials: SP
authors.lastname: Vasavada
authors.affiliation: Lerner College of Medicine, Education Institute, Cleveland Clinic, Cleveland, OH; Department of Urology, Glickman Urological and Kidney Institute, Cleveland Clinic, Cleveland, OH.
authors.forename: Raymond R
authors.initials: RR
authors.lastname: Rackley
mesh_terms: D003559:Cystostomy / Q000009:adverse effects / Q000379:methods; D004867:Equipment Design; D006801:Humans; D008422:Materials Testing / Q000379:methods; D012107:Research Design; D014546:Urinary Catheterization / Q000009:adverse effects / Q000379:methods; D062885:Urinary Catheters / Q000592:standards*; D014563:Urodynamics