A COMPUTER PROGRAM TO STORE AND ANALYSE AMBULATORY BLOOD PRES SURE DATA FOR THE REMLER M2000 RECORDER

M. BRENNAN, M. KEENAN, N. ATKINS, F. MEE, E. O'BRIEN The Blood Pressure Clinic, Charitable Infmary, Jervis Street, Dublin.

Ambulatory blood pressure measurement may have an impor-

tant place not only in the diagnosis and management of hyper-

tension (I), but also in the evaluation of new blood pressure

lowering drugs (2). The duration of drug action, the effect on

peak blood pressure with exercise, on blood pressure variabili - ty, on circardian rhythm, and on blood pressure after abrupt

withdrawal can be demonstrated.

Ambulatory measurements give a profile of blood pressure

begaviour that is more informative than conventional measure-

ments, but there are problems with data analysis not leaset of

which is the time required. Computerization of data should mi-

nimise this problem.

Direct intra-arterial ambulatory recording produces the

largest amount of data, each hourly mean being derived from up

to 5400 systolic and diastolic pressures (31, and computer fa-

cilities are essential for data analysis. Of the two commonly

used devices for non-fnvasi,ve measurement of ambulatory blood

pressure, the Del Mar Avionics Pressurometer and the Remler

M2000, the former can produce up to 200 blood pressure recor-

dings in 24 hours, and the Apple IIe has been used for data a-

nalysis (4). The Remler M2000, using a manually operated recor - der 2roduces 24 to 30 measurements of systolic and diastolic

blood pressure together with heart rate in a 12 to 15 hour pe-

riod of recording during waking hours, and this data has to be

manually analysed and presented. In this paper we describe the

use of a BBC microcomputer for the statistical analysis, plot-

ting and storage of ambulatory data obtained with the Remler

2000.

Proceedings of the Fiyth International Symposium or? Ambulatory Monitoring

Edited by

C. Dal Palu A.C. Pessina Professor of Medicine Associate Professor of Therapeutics

Clirlica h4edica I" Clirtica Medica I" Lniversira di Padova Urriversita di Padova

CLEW Editore

METHODS

The Remler 2000 consists of a standard pressure cuff,a mi - crophone, and amplifier, a transducer, a pneumatic switch as-

sembly and a leakoff valve (5). The patient inflates the cuff

using a standard inflation bulb at 30 minute intervals. At a

pre-set level above the patient's systolic pressure, the equi-

pment is energized. Pressure leaks off as calibrating pulses

and the arterial Korotkov sounds are recorded on a tape over

about 30 seconds. The-tape recorded information is fed to a de - coder comprising a frequency to DC convertor, amplifier, cali-

bration device and chart recorder. The arterial sounds are am-

plified and the technician may listen to the recorded sounds

with earphones. The calibrating pulses and arterial sounds are

converted to DC signals which drive the chart recorder pentand

systolic and diastolic pressures, and heart rate can be read.

It is our practice to plot heart rate and blood pressure aga-

inst time and to calculate the mean, peak, trough,standard de-

viation and coefficient of variation for systolic and diasto-

lic blood pressure and heart rate. The average time spent by

our technician on one Remler ambulatory measurement is 4 5 mi-

nutes, which is calculated as follows - attachment of equip-

ment and instruction of patient 12 minutes; decoding of tape

21 minutes; plotting of graph 10 minutes; statistical calcula - tions 5 minutes. One of the maim purposes of using a computer

was to reduce the costly expenditure on technician time in plot - ting the graph and making the statistical analysis,

The phys-5cian ordering a Remler completes a form documen - ting the personal details as listed in Table 1. FollowLng Rem-

ler decoding approximately 24 systolic and diastolic pressures

and heart rates are obtained (Table 2). A Basic program, com-

pacted for speed of execution, was wr3tten for a BBC Microcom-

puter with 32K memory and a twin 800K disk drive. The program

disk with a second floppy disk for data storage are inserted

in the disk drives. The program Main Menu (Table 3 ) lists the

options available to the operator. To enter a new record the

edit option is chosen. Table 1 appears on the screen and a re-

cord number and the personal details are keyed in, Table 2 is

Table 1 . P e r s o n a l D e t a i l s

, * I ( I 1 1 . : I 1000

O'GRADV ROSIE

Ei F I I I 190 1 98

I I 184 1 92

P#T 1, l SWT 1 , 5 120

GP BP - Blood p r e s s u r e recorded by genera l p r a c t i - t i o n e r .

C11 BP - F i r s t c l i n i c recorded blood p ressure .

I l l ! I . ; I XI5432

10 - 0 1 - 1934

W4Wj 70 , 2 kgs. W 168 cms.

4 y e a r s 0 months

I;1I11I1)I Hormal

IlQfQll 27.2 1 24 .8 HO

Echo - PWT - p o s t e r i o r w a l l t h i c k n e s s .

SWT - s e p t a 1 w a l l t h i c k n e s s .

ECG - S V 1 + R V S / S V I + RV6

~ 1 1 1 1 : l ~ I, HI D,

M e t o p r o l o l

208D

20 - 18 - 1984 W l 0 , 3 8 30 min,

c a l l e d up and ambulatory d a t a i s e n t e r e d . The s t a t i s t i c a l p a r a - meters and d a t a p l o t s genera ted by t h e Bas ic program a r e shown

i n Tables 4 and 5 . If any one i n t e r v a l r ead ing i s miss5ng t h e

p l o t r e c o r d s a blank and t h e s t a t i s t i c a l a n a l y s s s i g n o r e s t h a t

i n t e r v a l . P r i n t o u t s ' o f a r ecord c o n s i s t i n g of t h e p a t i e n t de-

t a i l s , s y s t o l i c and d i a s t o l i c p r e s s u r e s and h e a r t r a t e s , S t a t i - sties and g raphs a r e ob ta ined wi th a h igh speed sc reen dump

f a c i l i t y w i t h a d o t ma t r ix p r i n t e r . (Epson MX-100 111)

Records can be accessed u s i n g t h e p a t i e n t s name o r t h e

computer number of t h e r e c o r d ass igned a t t h e time ordered.The

d a t e of each ambulatory measurement i s d i s p l a y e d wi th t h e pe r -

l!UWM X15432 I l!IW 20 - 10 - 1984 W O'GRADV R O S I E I

Table 2. Remler Data

S y s t o l i c , d i a s t o l i c blood p res su res and hea r t r a t e .

PROGRAM M A I N MENU

1 . Edi t a record

2. P r i n t a sequence of records

3 . Create a Name Index F i l e of s o r t e d names

4 . P r i n t l i s t of so r t ed names

5. Search f o r a p a r t i c u l a r name

6 . Prepare d i s c t o hold Remler records

7 . Q u i t

Table 3 . Main menu

X15432 I l&W 20 - 1 0 - 1984 1 lJ&jj O'GRRDY R O S I E I S B P DBP H , R ,

Table 4. Remler Statistics

SBP - systolic blood pressure. DBP - diastolic blood pressure. HR - heart rate. M.A.P. - mean arterial pressure.

sonal details to identify which of a number of recordings for

a particular patient is being shown, a useful facility if the

computer number is unavailable. Using the BBC microcomputer we

have been able to reduce technician time for data analysis and

presentation form 15 to 5 minutes, and in addition the program

provides us with considerably more statistical data as well as

the facility for data retrieval.

DISCUSSION

The Remler M2000 has been used in our Blood Pressure Cli-

nic for indirect non-invasive measurement of ambulatory blood

1 lrlf(rl$.:(Q X15432 / w 20 - 10 - 1984 1 w O'GRADY ROSIE I

T a b l e 5 . Graph o f R e r n l e r Da t a

Ver t ica l a x i s - b l o o d p r e s s u r e . H o r i z o n t a l a x i s - t i - m e . S - s y s t o l i c b l o o d p r e s s u r e . D - d i a s t o l i c b lood

p r e s s u r e .

p r e s s u r e i n o v e r 1700 p a t i e n t s . W e f i n d t h e s y s t e m s a t i s f a c t o -

r y b e c a u s e it i s a c c u r a t e ( 6 ) and r e p r o d u c i b i l e (71 , h a s good

p a t i e n t a c c e p t a n c e ( 8 ) , and b e c a u s e it p r o v i d e s a pe rmanent t a -

p e r e c o r d o f Koro tkov sounds which p e r m i t s t h e v e r i f i c a t i o n o f

r e c o r d e d measurements . However, t o o b t a i n s a t i s f a c t o r y r e s u l t s

w i t h t h e R e m l e r M2000, c o n s i d e r a b l e a t t e n t i o n mus t b e d i r e c t e d

t o a p p l y i n g t h e r e c o r d e r t o t h e p a t i e n t , i n s t r u c t i n g t h e pa-

t i e n t i n i t s u s e , decod$ng t h e t a p e , m a i n t a i n i n g t h e equ ipment

and r e c o g n i s i n g ( a n d i f p o s s k b l e c o r r e c t i . n g ) t h e ' w e a r and

t e a r ' f a u l t s t h a t d e v e l o p i n t h e r e c o r d e r , t h e mic rophone and

t h e d e c o d e r . To a c h i e v e o p t i m a l r e s u l t s f r om t h e sy s t em w e ha-

v e found it e x p e d i e n t t o employ a f u l l - t i m e t e c h n i c i a n . T h i s

has resulted in a worthwhkle improvement in the quality og re-

cordings (Table 6 ) but it adds considerably to the cost of am-

bulatory measurement.

The use of a microcomputer is the first of two projects

the purpose of which is to reduce the estimated 4 5 minutes of

technician time. It has perrn3tted the saving of 1 0 minutes,and

in addit2on provides extra statistical calculations, as well

as providing a facil5ty for correlations on different parame-

ters of our patient population. The ease of providing a copy

for the referring doctor and for the patients notes is a fur-

ther advantage. In the second project we are attempting to re-

duce technician time further by linking the Remler decoder di-

rect-ly to the microcomputer so that it will not be necessary

to key in the decoded measurements to the computer.

Table 6.

- -- -

[ Year Total recordings Overall failure Failure Rate I I

I

I rate I Equipment / Patient I

Table 6. Annual Remler Failure Rate

Equipment - Failures due to equipment malfunction. Patient - Failures due to patient error.

REFERENCES

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FITZGERALD DJ, O'PIALLEY K, OtBRIEN E. Disparity between clinic (CBP) and ambulatory blood pressure (ABP) in re- sponse to antihypertensive therapy. (Abstract) Clfn Phar- macol Ther 1984; 35:140.

RAFTERY EB, MELVILLE DI, GOL'LD BA, MANN S,WHITTINGTON JR. k study of the antihypertensive action of xipamide using ambulatory intra-arterial monitoring. Br J Clin Pharm 1981; 12: 381-385.

BOLEN K, W S E Y L, GIFFORD R. Interfacing the Del Mar A- vionics Model 1978 PI11 system with the Apple IIe compu- ter. In: Weber P I A , Drayer JIM, eds. Ambulatory blood pres- sure monitoring. New York: Springer-Verlag; Darmstadt : Steinkopff Verlag, 1984:35-41.

FlTCGERALD DJ, O'CALLAGHAN WG, O'MALLEY K, O'BRIEN ET.Ac curacy and reliability of two indirect ambulatory blooa Fressure recorders: Remler M2000 and Cardiodyne Sphygmo- log. Br Heart J 1982; 48:572-9.

COWAN RM, SOKOLOW M, PERLOFF D. Methodological considera- tion in determining the accuracy of an indirect blood preg sure recorder. In: Weber MA, Dryer JIM, eds. ambulatory blood pressure monitoring. New York: Springer-Verlag; Dar - mstadt: Steinkopff Verlag, 1984:241-247.

FITZGERaLD DJ, O11.mLLEY K, O'BRIEN E, Reproducibili\ty of ambulatory blood pressure recordings. In: Weber Ma, Dra- yer JIM, eds. Ambulatory blood pressure monitoring, New Tork: Springer-Verlag; Darmstadt: Steinkopff ~erlag,1984: 71-74.

FITZGERALD DJ, O'DONNELL D, BRENNAN M, O'ELALLEY K,OIBRIEN E. The accuracy and reliability of the Del Mar Avionics Pressurometer 111. Journal of Hypertension. In press.

ACKNOWLEDGEEIENT

A grant from the Royal College of Surgeons in Ireland is

gratefully acknowledged.