Brifish Journal of Urology (1986). 58,327-331 IQ 1986 British Journal of Urology

A Computerised Urodynamic System

B. G. BEST, S. R. JOHNSTON, J. A. KENNEDY and W. G. G. LOUGHRIDGE

Department of Urology, Belfast City Hospital, Belfast

Summary-A new urodynamic investigation system, based on a microprocessor, iS described. The design principles, versatility and advantages of the equipment are discussed. It is concluded that this system offers significant benefits to the urodynamic unit for both routine and research work.

Our understanding of lower urinary tract function has advanced rapidly over the past decade. New concepts appear in the literature almost monthly and increasingly complex analyses are required. In the light of these developments, previous cases often have to be reviewed, and this requires an efi- cient file system. We felt that the stage had been reached for the computerisation of urodynamics to facilitate data analysis and file handling. Our initial thought, to interface a computer to an existing sys- tem, seemed unnecessarily complex as it would in- volve a mixture of analogue and digital signals for much of the procedure. We therefare designed a new urodynamic system using a powerful micro- computer, with integral VDU monitor and dual disk drives, linked to a dot matrix printer.

Materials and Methods

The microcomputer is an ACT Sirius 1, with its 800 x 400 resolution monitor and dual disk drives (which use 5.25 inch floppy disks). The printer is an Epson MX80 F/T 111.

The Sirius 1 was chosen for its 512K RAM memory, needed for storage and analysis of the large amount of incoming data, and its high resolu- tion monitor which permits fine detail to be dis- played. The operating program disk remains in one drive while data is stored on to, or read from, disks in the other drive.

Based on a Poster Demonstration at the 41st Annual Meeting of the British Association of Urological Sur- geons in Eastbourne, July 1985

BLAD DERIU RETH RAL

RECTAL MICRO-COMPUTER

FILLING VOLUME

t \ FLOW RATE & VOLUME 6-7

Fig. 1

The dot matrix printer is used to draw the graphics and print the results.

Programs are written in Forth and Machine Code computer languages, using the CP/M operat- ing system.

The bladder and urethral pressures are measured by Gaeltec catheter-mounted transducers which, owing to their very fast response times, enable short duration events to be recorded. The rectal pressure is measured by an external Gaeltec trans- ducer attached to the usual fluid filled line. A weight transducer records filling volume (Fig. 1). The flow meter is unique and will be discussed in detail later.

The input signals, which are in analogue form, are filtered to an upper range of 30Hz depending on the frequency response of the measuring equip- ment. They pass to an analogue-digital converter which samples the waveform at 8 to 64 times per second and expresses the results in a computer readable form (Asbury, 1983). The sampling rate can be altered at will to the optimum for each sig- nal without interrupting the recording. The digital

321

328 BRITISH JOURNAL OF UROLOGY

CHANNEL

6 7

- - - PRE-VOID

CHANNEL

6 7

l- I I .

- INCREASED - PRESSURE - I - -

POST-VOID Fig. 2 Flow meter.

signals are stored in the microcomputer memory and are used to produce a “real-time” visual dis- play. On completion of the urodynamic assess- ment, the data are reviewed and analysed, as desired, by the computer. A printout (A4 size) of the curves and their analyses is then obtained. The data can be directly stored on computer disks, per- mitting future additional analysis.

The flow meter (Fig. 2) is a one-litre plastic jug with a fine bore side arm, connected to a pressure transducer. A removable baffle eliminates turbu-

lence. As the level of urine rises during micturition, the air in the side arm is compressed. The rate of change and total rise in pressure are computed into flow rate and volume. The recording automatically begins with the first change in pressure. A memory buffer holds data for 10s and the computer reads the preceding 10 s after initiation. This ensures that the true start of micturition is included. The cali- bration allows for rates of up to 50ml/s and volumes of up to 1000 ml. The response and oscilla- tion times have been tested against known constant flows of square wave pattern. The equipment is accurate to within 1% for both rata and volume. The flow meter is also available as a separate port- able unit, using a battery powered Epson HX 20 computer.

The urodynamic routines are stored on floppy disks and include the operating and mathematical instructions for the various types of analysis.

Our standard program consists of uroflowmetry, filling and voiding cystometry, and urethral pres- sure profilometry. At present we do not use EMG recording. However, if required, the EMG signal may be fed into channel 3 after appropriate pro- gram modification. Analytical parameters may be assessed at any part or parts of the traces. These parameters include values of pressure and volume, flow rates, areas under curves, slope gradients and urethral lengths. Automatic selection of maximum values is a useful feature. The appropriate program is loaded at the start of the urodynamic session. Patient details are typed in on the computer key- board. The actual clinical procedure is the same as for other systems. Briefly, the patient is asked to at- tend the clinic with a full bladder and an initial flow rate is obtained. The patient then lies on the exami- nation couch and the rectal line ( 5 Fg) is inserted. The filling catheter (10 Fg) and the double trans- ducer catheter (6 Fg) are passed simultaneously under urethral anaesthesia. Any residual urine is noted. The proximal transducer is placed at the dis- tal sphincter while the distal transducer lies free within the bladder; the catheter is kept in position by attaching it to the arm of the catheter puller. Filling cystometry is performed and the filling cath- eter is then removed. When the patient is moving from the supine to standing position, the catheter is held in place by the operator or nurse. Voiding cys- tometry is performed. The urethral profile is obtained using an electric motor catheter puller to ensure a constant and accurate rate of withdrawal. Events are marked on the screen as they occur, e.g. desire to void, using the appropriate key on the keyboard.

A COMPUTERISED URODYNAMIC SYSTEM 329

Firstname

Sex Female Date 13/11 184

Age 39

Fig. 3 A. Filling and voiding profile of patient with primary detrusor insta- bility. B. Static urethral profile of patient with primary detrusor insta- bility.

n 100 cm Water

v Pur

B

, iVoided Volume=O

I

Samples I sec

Surname

I C I U No. 84333 I IPves :

Consultant JAK

IPabd I

25

ISamDles I 1 100 cm Water

5 urname Firstname

Sex Female Date

Age 39

C I U No. 84333 Consultant JAK Ipves I

A L =29 A L =28 C Z L 114 CZL =16 F L =28 F L =27 MUP =53 MUP =50 IPdet I AREA=821 AREA=770 MUCP=51 MUCP-48 I

l e I

330

C I U No. 84149 Consultant wgql

BRITISH JOURNAL OF UROLOGY

Pves

A

Fig. 4 A. Filling and voiding profile of patient with outlet obstruction. B. Static urethral profile of patient with outlet obstruction.

B

100 cm

Surname First name

Sex Date

Age 35

Pur- Pvem I FILLING & VOID INC

Voided Volume=O

Pa bd

Pdet

filling volume

400

Iflow

7 44

Samples

100 cm

Surname Firstname

Sex ' Male Date

Age

C I U No. 84189 Consultant wggj lpves I

P I- b

1 I F b d I Pdet

A COMPUTERISED URODYNAMIC SYSTEM 33 1

We use a double transducer catheter routinely, though single and triple transducer catheters are used in some of the research studies. The double transducers allow synchronous measurement of bladder and urethral pressures. This is especially valuable in urethral profilometry as it allows detru- sor activity to be monitored during the profile.

Results We have used this system since August 1982. Apart from a few initial design modifications and some alterations to the routine program, we have not encountered any disadvantages. Many advantages have become apparent as experience has been gained. Ease of use has resulted in shorter pro- cedure times, allowing 66% more patients to be studied in a similar preceding period. The compact- ness of the unit and the simplicity of the flow meter, with automatic start, result in a more relaxed patient. Many patients, in fact, pass the time watching the screen; detrusor instability can then easily be explained to the patient and a biofeedback treatment programme started, if appropriate. The nursing staff have found the flow meter very easy to clean quickly and to set up for the next patient. Immediate access to patient records stored on disk has been helpful at follow-up clinics.

Two examples of urodynamic studies are shown. Figure 3 shows the filling cystometric and static urethral profile traces of a 39-year-old female suf- fering from primary detrusor instability. Figure 4 shows the urodynamic findings in a 35-year-old man with symptoms of outlet obstruction. He was unable to void at the clinic. Filling cystometry shows a detrusor pressure of 44cm of water at a volume of 295ml. Urethral profilometry shows a double (pre-sphiwteric) peak suggestive of bladder neck hypertrophy. This was confirmed at cysto- urethroscopy.

Discussion A major benefit of this system is the ease with which any type of analysis may be obtained, no matter how complex. When new concepts demand new mathematical formulae, the program may be

altered accordingly or a separate one written. The system is “user friendly”, i.e. no computer knowl- edge is required by the operator. However, if pro- gram writing is to be undertaken, considerable expertise is needed. If this is not available in the hospital/university, Gaeltec Research Ltd will sup- ply programs, from their program library, with the system and they will write programs to meet speci- fic requirements.

An additional benefit is that it is far more than just a urodynamic system. It is still a powerful microcomputer and can be used for several differ- ent functions in the urological unit such as word processing, data files, statistics. Many independent commercial computer programs are immediately compatible with the urodynamic records because of their common program language and operating systems.

The cost of the complete system is similar to that of conventional 6-channel machines. The running costs are low as fanfold computer paper is consi- derably cheaper than flow chart paper.

In conclusion, the inherent versatility and capa- city of this system offers significant benefits for rou- tine and research urodynamic studies. The urological unit also benefits from its microcom- puter functions.

Acknowledgements We thank Donald MacLachlan, BSc, ARCS, of Gaeltec Re- search Ltd, Dingwall, Scotland, who undertook the design and production of the system.

Mr B. G. Best was in receipt of a DHSS Research Fellowship.

Reference Asbury, A. J. (1983). ABC of computing. British Medical Jour-

nal, 286, 1799- 180 1.

The Authors B. G. Best, FRCS, Senior Surgical Registrar. S. R. Johnston, FRCS, Consultant Urological Surgeon. J. A. Kennedy, MCh, FRCS, Consultant Urological Surgeon. W. G. G. Loughridge, MA, MD, FRCS, Consultant Urological

Surgeon.

Requests for reprints to: S. R. Johnston, Department of Urol- ogy, Belfast City Hospital, Lisburn Road, Belfast BT9 7AB.