Linearisation of a urinary flow transducer

Development of a low-cost flow meter to grade the maximum flow rate

We developed an inexpensive flow meter to grade the maximum flow rate of individuals at locations other than the clinical setting. This flow meter consists of a funnel connected to a collecting tube with several exit ports. Urine directed into this tube flows through one or more ports and is collected in a measuring cup to measure the voided volume. The number of ports emitting the liquid is a measure for the flow rate. We made four experimental models to test and compare some of the physical properties. One of these models was selected as a prototype and was tested in five healthy volunteers. All volunteers voided repeatedly in a standard rotating disk flow meter and in this prototype to test its accuracy. The response time of the experimental models depended on the outlet resistance of the exit ports and the volume of the collecting tube. In two models, this time was comparable with that of currently used volume-based electronic flow meters (approximately 2 seconds). In healthy volunteers, the maximum flow rates graded with the selected prototype and those measured with the rotating disk flow meter showed good agreement (difference=0.4+/-2.6 mL/s; mean+/-SD). The low-cost flow meter may be used repeatedly to grade the maximum flow rate at private and familiar locations (for example, at home), which may increase the accuracy of evaluating the urinary stream in patients with lower urinary tract symptoms.