Bio-Medical Engineering. Strömungsfragen der Medizin

79 Pages·1970·2.155 MB·German

by  Heinz S. Wolff, Alexander Naumann (auth.)

ARBEITSGEMEINSCHAFT FUR FORSCHUNG
DES LANDES NORDRHEIN-WESTFALEN
NATUR-, INGENIEUR- UND GESELLSCHAFTSWISSENSCHAFTEN
181. SITZUNG
AM 2. JULl 1969
IN DUSSELDORF
ARBEITSGEMEINSCHAFT FOR FORSCHUNG
DES LANDES NORDRHEIN -WESTFALEN
NATUR., INGENIE UR· UND GE SELLSCHAFTSWI SSEN SCHAFTEN
HEFT 203
HEINZ S. WOLFF
Bio-Medical Engineering
ALEXANDER NAUMANN
Stromungsfragen der Medizin
HERAUSGEGEBEN
1M AUFTRAGE DES MINISTERPRAsIDENTEN HEINZ KUHN
VON STAATSSEKRETAR PROFESSOR Dr. h. c. Dr. E. h. LEO BRANDT
HEINZ S. WOLFF
Bio-Medical Engineering
ALEXANDER NAUMANN
Stromungsfragen der Medizin
SPRINGER F ACHMEDIEN WIESBADEN GMBH
ISBN 978-3-663-00460-8 ISBN 978-3-663-02373-9 (eBook)
DOI 10.1007/978-3-663-02373-9
© 1970 by Springer Fachmedien Wiesbaden
Urspriinglich erschienen bei Westdeutscher Verlag GmbH, K6ln nnd Opladen 1970
Inhalt
Heinz S. Wolff, Head of the Division of Bio-Medical Engineering, in
the National Institute for Medical Research, London
Bio-Medical Engineering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Diskussionsbei trage
Professor Dr. med. Franz Grosse-Brockhoff; Dr. Heinz S. Wolff;
Staatssekretar Professor Dr. h. c., Dr.-Ing. E. h. Leo Brandt; Profes
sor Dr.-Ing. Franz J. Meister; Regierungsrat Dr. rer. nat. T. Hoch
muth; Professor Dr. phil., Dr.-Ing. E. h. Fritz Schroter; Professor
Dr.-Ing. August Wilhelm Quick; Dipl.-Ing. Horst Penschuck 19
Alexander Naumann, Aachen
Stromungsfragen der Medizin
Einleitung ............................................... 27
Der Blutkreislauf in den Adern .............................. 30
Stromungsuntersuchungen an kiinstlichen Herzklappen .......... 41
a) Aortenklappenprothesen ................................ 42
b) Mitralisprothesen ....................................... 51
Ober die Beanspruchung des Blutes durch Stromungsvorgange
(Hamolyse) .............................................. 53
Schlu6bemerkung ......................................... 63
Summary................................................ 65
Resume ................................................. 66
Literatur ................................................ 67
Diskussionsbei trage
Staatssekretar Professor Dr. h. c., Dr.-Ing. E. h. Leo Brandt; Profes
sor Dr. med. Robert Miirtz; Professor Dr. phil. Alexander Naumann;
Dr.-Ing. Carl Kramer; Dr. Heinz S. Wolff; Professor Dr. med. Franz
Grosse-Brockhoff; Dr. rer. nat. Hermann Stehr; Professor Dr. med.
Jakob Schoenmackers; Professor Dr. med. Hellmut Ippen ........ 69
Bio-Medical Engineering
Von Heinz S. Wolff, London
I thought that it might be useful if I were to start my lecture by telling
you a little about my personal background and the setting within which my
laboratory works.
I am basically a physiologist with some training in physics who for vir
tually the whole of his professional life has been engaged in the application
of technology, first to physiological problems and more recently to problems
which arise in clinical practice. I work for an organisation called the Medical
Research Council which in company with four other research councils deal
ing with science, agriculture, social science and the natural environment, is
financed almost entirely from public funds through the Department of Edu
cation and Science. The Medical Research Council maintains laboratones
throughout the country, most of them concerned with their own speciality.
In addition in London there is the National Institute for Medical Research
which itself is split into about 17 divisions, each of which has its own special
subject such as for instance low temperature biology, human physiology,
physiology and pharmacology, organic chemistry and last but I hope not
least, bio-medical engineering.
It is not uncommon in England for university departments or laboratories
particularly concerned with research into the life sciences to have instrumen
tation departments which have been set up to cater specifically for their own
instrumentation needs. The National Institute for Medical Research is no
exception to this and maintains an engineering division, the primary duty
of which is to support the research of the other divisions in the Institute.
My own division has been organised along rather different lines in as far
as we have no direct responsibility towards any other laboratory or organi
sation but are free to engage in an activity which I have called "prospective
technology". Let me explain this term.
The normal relationship between the engineer or technologist and the
biological scientist is for the latter to present a problem to the former for
solution. The engineer brings his technological knowledge to bear and solves
the problem using such techniques as he thinks are appropriate. This arrange
ment, whilst it is in general satisfactory and, incidentally, employs by far
the greater portion of bioengineers, in my opinion is not on its own sufficient
8 Heinz S. Wolff
to support the rapid introduction of technology into medicine. I am always
impressed with the enormous gap which appears to exist between what tech
nology can do and the technology which is actually applied. In a situation
where the problem posers i. e. the doctors and biological scientists are often
themselves almost totally unaware of recent technological developments, I
suspect that a situation arises where problems are no longer posed in the
right manner, because most people are not very good at extrapolating appre
ciably outside the range of their experience. It may, therefore, be necessary
to employ a mechanism by which workers who are aware of recent develop
ments in technology examine the biological and medical front systematically
for areas where they believe it can be applied successfully.
This means first putting up a conceptual model, then indulging in activity
perhaps analogous to market research to find out whether the idea is likely
to find any support, then to make some actual apparatus and finally to
convince industry that the project may be worthy of commercial exploita
tion. Such activity in my opinion could lead to a more rapid introduction of
technology itself, but is on the other hand of a speculative nature, requires
an indulgent employer and an organisation which is sufficiently large to
handle a number of problems simultaneously so that the disappointment of
failure on one sector of the front does not dishearten one completely. The
projects which I shall describe have all initially arisen within the laboratory
although we were of course aware that not dissimilar work was going on
elsewhere.
I shall deal with the basic criteria which we set up for the design of patient
monitoring equipment and then follow this with a description of a new kind
of equipment designed to make it possible to investigate physiological and
environmental parameters associated with every day life. I shall then con
cern myself with what I regard as the very real problem of communication
between machines and the people who have to act upon their information
and finally I would like to draw your attention to a major omission from
the biomedical engineering research projects in the majority of the developed
countries.
Patient monitoring can be defined as the acquisition of physiological sig
nals from patients who are very ill and the display of these signals in such a
manner as to allow the staff responsible for the patient's care to take the
appropriate action. Right at the start I would like to draw the distinction
between physiological measuring equipment which is arranged in such a way
that it requires action or initiative on the part of the nurse or doctor to
"read" the instrument and monitoring equipment which is extrovert in its
nature and displays the information in such a way as to bring it to the notice
Bio-Medical Engineering 9
Fig. 1: Thermometer type indicators which give a histogram type of display of the
patient's overall condition
of the appropriate people whether they happen to want to take a reading
or not. We felt that to compensate for shortage of nurses, lack of motivation
and sometimes lack of measuring skill, it was monitoring equipment which
was required and that the measuring equipment had a limited utility in the
research world or in situations where staff were really plentiful. It was not
unnatural, therefore, that we first turned our interest to devising a form of
information display which would draw attention to itself and which would
be capable of giving a qualitative profile of the patient's condition even
when examined from some distance. The solution which was found to be
most acceptable was to transfer the magnitude of each measurement into the
length of a column of light arranged in a device to look rather like a ther
mometer (Fig. 1). If five such indicators are mounted side by side and if the
scales are arranged in such a way that normal values are fairly near the centre
of each scale, then a form of histogram will be presented for each patient. Ab
normally high or low readings will be very noticeable and will stimulate the
nurse to examine the patient a little more carefully. Superimposed on each
column of light are two adjustable markers which define the upper and lower
limits outside which the installation should produce an alarm or warning, so
as to draw the attention of the staff to rapid deterioration. Because these
markers are superimposed on the column, it is always possible to see what
10 Heinz S. Wolff
..
Fig. 2: Bedside Unit showing removable modules, each of which processes the signal from
a particular transducer. The modules can be readily interchanged, if a different
selection of measurements is required, or if a fault has developed
Bio-Medical Engineering 11
margin of safety still remains and if possible to take corrective action before
a potentially dangerous situation has actually developed. Another advantage
of the indicator is that being self-luminous, it is not dependent on external
illumination, which makes it possible to lower the ambient light in the ward
at night, thus avoiding additional strain on the patient by disturbing his
accustomed diurnal rhythm.
The next problem was to decide what measurements to make. It seemed
wrong to us to make a system which had certain measurements permanently
built into it, but instead we wanted to foster an attitude where measurement
was prescribed with the same care as treatment. This led to the design of
the so-called bed-side unit (Fig. 2) which is an assembly into which seven
modules can be placed, each module completely enclosed and containing
appropriate circuits to process a signal from a particular kind of transducer.
It thus becomes a nursing task to set up a system according to the doctor's
requirements merely by taking the appropriate modules for setting up say,
systolic and diastolic blood pressure, skin temperature and respiration rate
from a library of stock modules, to insert these in the bed-side unit, to attach
the appropriate transducers to the patient and to fix the appropriate scales
on to the indicator. These tasks can all be performed without any tools and
with the absolute minimum of technical training. The last item which had to
be designed was a device for providing a permanent record in the form of a
chart not dissimilar to the chart at present kept by the nursing staff. This
recorder (Fig. 3) can be hung on the wall close to the patient rather like a
picture so that it serves not only to display "historical" information but
also to indicate the trend of the measurement. In many cases it is the trend
which is in itself more important than the absolute value.
The highly modular construction of the equipment has one further advan
tage. In our experience no single factor is more likely to produce rejection of
the equipment than repeated technical failures which the staff are unable to
correct without the aid of a technician. Such failures produce not only a
reduction in faith in the equipment but also a loss of face on the part of the
staff. By providing a test programme (Fig. 4) and very simple test instru
ments as part of the installation it is possible to guide the nurse through a
procedure by means of which she can within a period of a very few minutes
identify the lead, module, indicator or transducer which may have failed
and to replace it by a spare. From the psychological point of view the ability
of the night nurse to say proudly to the ward sister next morning that there
had been a fault in Mr. Jones' heart rate indicator but that she had repaired
it, could totally change the climate of acceptance within which the equip
ment works.