Momentum Method for Measuring Uroflow Parameters and the Uroflow Flowmeter

This invention relates to instrument for human uroflowmetry. Uroflowmetry is an important part of urinary flow dynamics inspection, which requires measurement in real time of the flow rate, voiding time, voided volume and the flow rate as a function of time. These uroflowmetric results contribute not only to diagnosis of urinary obstruction, but also to objective evaluation of the effect of medical and surgical treatment and to the observation of the disease process.

There is no way except by means of accurate uroflowmeter measurements to obtain accurate and reliable uroflowmetric parameters. There are several manual or automatic uroflowmeters for medical use based on volume, gravity or dynamic balancing principles currently in use, but none of them provides satisfactory dynamic uroflowmetric results.

The principle of the URODYN 1000 automatic uroflowmeter made by Denmark DANTEC Electronics Ltd., for example, involves passing voided urinary flow is led onto a constant speed disk driven by a DC motor, with the electrical energy needed to keep the disk rotating at a constant speed being proportional to the flow rate. But the sensitivity of the flowmeter is not high, particularly at the starting or ending stages of voiding.

The object of this invention, therefore, is to provide a novel uroflow measurement method and uroflowmeter with higher sensitivity, satisfactory to measure dynamic uroflowmetric parameters.

The purpose of this invention is to define the dynamic characteristics of urinary flow by impulse momentum. The principle is as follows. The urinary flow with certain speed impact on an elastic cantilever and produce a displacement of the cantilever. The displacement is proportional to the urinary flow impulse momentum. The displacement of the cantilever is detected by a displacement transducer (capacitive, inductive or eddy current type). The output electrical signal of the transducer, after conventional waveshaping, amplification, and A/D conversion, is fed to a microprocessor to be processed. A printer prints out the urinary flow curve.

The invention will now be described with reference to the accompanying drawings, FIG. 1 of which is a side elevation, partly sectionalized, of a preferred embodiment and mode of the uroflowmeter apparatus of the invention;

FIGS. 2A and 2B are respectively a transverse section and a top elevational view of the urinal portion of the apparatus of FIG. 1;

FIGS. 3A and 3B are respectively side and top views of the elastic cantilever of the apparatus;

FIGS. 4A and 4B are respectively a transverse section and top view and FIGS. 5A and 5B, side and top views of displacement limiter stops for the cantilever; and

FIG. 6 is a schematic flow chart of the signal processing technique used with the system of FIG. 1.

Referring to the drawings, FIG. 1 shows the overall construction of the uroflowmeter in preferred form with the abovementioned urinal illustrated at 1, the elastic cantilever at 2, a displacement measuring transducer at 3 for producing a signal corresponding to the cantilever displacement, and upper and lower displacement limiter stops for the cantilever 2 at 4 and 5, respectively. The body 6 of the urinal 1, FIGS. 1, 2A and 2B, is shown in conical form mounted upon a depending urinary flow tube 8, and with an upper apertured convex guiding surface 7.

As more particularly shown in FIGS. 3A and 3B, the elastic cantilever 2 mounted below the slotted upper stop strip 4, FIGS. 4A and 4B, and extending therebeyond (to the right in FIG. 1), is provided with an upwardly extending splash deflector sheet 10 and a terminal extension comprising a convex urine flow impact surface 9. The lower cantilever beam displacement stop or limiter sheet is shown at 5, FIGS. 1, 5A and 5B.

The uroflowmeter transducer system and appropriate signal processing procedure of the invention will now be described.

After flowing into the urinal 1 the urine comes into contact with the apertured convex guiding surface 7 and flows through the apertures therein into and along the tube 8, impacting upon the terminal convex surface 9 and deflecting the elastic cantilever 2. The displacement of the cantilever is sensed by the transducer 3 and converted into an electrical signal which is sent to the signal processing system, FIG. 6. The limiter strips 4 and 5 protect the elastic cantilever from excessive displacement due to excessive flow and self-excited oscillation. The urinal and the limiters 4 and 5 may be made of hard plastic material and the elastic cantilever 2 of beryllium bronze. The sheet 10 may be made of corrosion resistant metals, such as stainless steel etc.

The working procedure or flow of the signal processing system, shown in FIG. 6, is as follows, with the uroflowmeter providing up to seven data outputs: maximum flow rate Rmax, average flow rate R, voiding volume V, voiding time T.sub.v, flow time T.sub.f (with the voiding time probably containing some time To when R.sub.i =O), and time to maximum flow rate T.sub.Rmax.

The signal processing system comprises a conventional amplifying circuit within the transducer assembly 3, and A/D conversion circuit within a conventional microprocessor, as labelled in FIG. 6, and the conventional printer ("Print Results" in FIG. 6). The voltage signal of the displacement transducer 3 is proportional to the instantaneous flow rate R.sub.1. The signal processing system samples the output voltage signal of the displacement transducer 3, labelled "Signal" in FIG. 1, and after amplification and A/D conversion, the signals are calculated by the microprocessor in accordance with the flow chart of FIG. 6, which finally prints out the above-mentioned seven data outputs.

As illustrated in the signal processing flow of FIG. 6, once the elastic cantilever deflects under the urinary flow impact, the displacement transducer generates the voltage signal. The signal processing system begins timing and sampling (bottom of FIG. 6), as is well known, at regular intervals. This produces at each time of sampling a value of instantaneous flow rate (R.sub.i), which is stored in memory. The maximum flow rate is obtained ("Find R.sub.max ", FIG. 6) after comparison of the different values of R.sub.i. The time to maximum flow rate T.sub.Rmax is also stored in the memory. After the conclusion of voiding, the sampling stops and all of the data stored is processed. The sum of all instantaneous flow rate values (".SIGMA.R.sub.i ", FIG. 6) is divided by the number of sampling times n and equals the average flow rate (R=.SIGMA.R.sub.i /n), designated by "R" in FIG. 6). The voiding volume V is determined by integration V=.intg.R.sub.i dt labeleld "Integration to Find V" in FIG. 6. The voiding time T.sub.v ("T.sub.v " in FIG. 6) is defined as the time between the begining and ending of sampling. The time when R.sub.i =O is determined as To. T.sub.v minus T.sub.o equals the flow time T.sub.f bottom of FIG. 6.

The uroflowmeter of the invention is thus based on an impulse momentum method of measurement and reflects the dynamic process of voiding, featuring high sensitivity and reliable performance.

Modifications will occur to those skilled in this art and are considered to fall within the spirit and scope of the invention as defined in the appended claims.