PurposeTo assess the risk factors for developing urinary retention after removal of the urethral catheter on postoperative day 1 in benign prostatic hyperplasia patients who underwent Greenlight HPS laser photoselective vaporization prostatectomy (PVP).Materials and MethodsThe study included 427 men who underwent Greenlight HPS laser PVP between 2009 and 2012, excluding patients in whom a catheter was maintained for more than 1 day because of urethral procedures. In all patients, a voiding trial was performed on postoperative day 1; if patients were unable to urinate, the urethral catheter was replaced before hospital discharge. The patients were divided into two groups: early catheter removal (postoperative day 1) and late catheter removal (urethral catheter reinsertion). Preoperative and perioperative parameters were compared between the groups.ResultsCatheters were successfully removed in 378 (88.6%) patients on postoperative day 1. In 49 patients, the catheters were reinserted and removed a mean of 6.45±0.39 days after surgery. In a multivariate analysis, a history of diabetes was the most significant predictor (p=0.028) of failure of early catheter removal, followed by operative time (p=0.039). There were no significant differences in age, prostate volume, International Prostate Symptom Score, or urodynamic parameters between the two groups.ConclusionsIt is feasible, safe, and cost-effective to remove the urethral catheter on postoperative day 1 after Greenlight HPS laser PVP, but the procedure should be done carefully in patients who have history of diabetes or an extended operative time.

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In this study, we suggest an optimization process for the characteristics of seat foam to improve the seating comfort. The items selected for the optimization of the characteristics of seat foam are the initial comfort, the static comfort and the transient comfort. The evaluation items selected for optimization are the modulus irregularity factor, the amount of compression and the amount of sagging. The properties of the foam material which are the object of the optimization are simulated using fitting equations. The variables which have important influences on the expression for the foam characteristics are selected as the factors for the optimization. Additionally, the normalized relaxation modulus, which describes the time-dependent deterioration in the foam characteristics, is selected as one of the key factors. To design the experiments, a central composite design is selected from among the response surface methods. A second-order regression model is used to create the response surfaces, and the mechanical characteristics of the foam materials that influence the initial comfort, the static comfort and the transient comfort are evaluated by analysis of the response surfaces. It is possible to produce data on the foam characteristics which satisfy all optimization items by optimum designs.

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