RESEARCH AND
DEVELOPMENT OF MEDICAL INSTRUMENTS AT BARC
Dr.
G. D. Jindal*
The Bhabha Atomic
Research Centre (BARC), Mumbai had initiated research and development
programme for medical instruments including nuclear medical and
bio-medical systems almost 40 years ago. This programme resulted
in import substitution for a number of medical instruments such
as Thyroid Uptake Monitor for studying the function of thyroid
gland, Reno gram for assessment of the functioning of kidneys,
Slow and Fast Gamma Scanner for imaging of internal organs of
the body, M-mode Echo-cardiograph for studying the motion of different
parts of the heart, electromyography for studying the diseases
of nerves and muscles of the body and Magnetic Stimulator for
painless stimulation of nerves in brain and spinal cord to assess
the functioning of the nerves.
It also led to
a pioneering research work in the field of impedance plethysmography,
electromyography, data acquisition and processing in gamma ray
scintigraphy and variability analysis. Some of these systems are
produced locally with technical know-how from BARC and many are
still in use in their original form. Presently the emphasis is
on development of new modalities for the non-invasive assessment
of different diseases of the body. Several novel and state-of-the-art
instruments have been developed, namely, Impedance Cardiovasograph,
Cardiac Output Monitor and Medical Analyzer. These systems are
based on the principle of electrical impedance plethysmography
and use different data acquisition and processing methods for
the diagnosis of diseases of cardio-vascular and autonomous nervous
systems.
Impedance Cardiovasograph
Impedance cardiovasograph
detects obstructions in the flow of blood in the arteries as well
as veins of the hands and legs of a human being. As we know, blood
flows in the arteries and veins. Formation of a close loop of
blood circulation is very essential for the survival of the living
body as it supplies the nutrition and oxygen and removes the waste
products from all its tissues. To maintain proper blood circulation
the heart, lungs, arteries and veins need to be in a healthy condition
as the heart acts as a pump to maintain blood flow in closed loop,
the lungs provide oxygen to the blood, the arteries carry the
blood to all the tissues of the body while the veins remove the
waste products from the tissues. Any obstruction to the flow of
blood in the arteries or veins leads to inadequate supply of the
nutrition and waste removal causing either pain, non-healing wounds
and decay of tissues or swelling, bulging or bursting of superficial
veins and skin infection of the respective limb. In the conventional
procedure to detect obstructions in the blood flow, a high-density
substance is injected in the blood stream with the help of a catheter
and then X-ray pictures are taken sequentially to visualize the
bocks in the flow of blood. This procedure is commonly known as
angiography and has an inherent risk of 0.1 to 1 per cent of either
death of the subject or complicating the disease. Impedance cardiovasography
detects these blocks or obstructions without causing any harm
or discomfort to the patient as it is carried out with the help
of surface electrodes in contact with outside surface of the body
and no part of the system pierces the body. No material is injected
inside the body.
The instrument
shown in the picture measures the electrical impedance of any
segment of the body and records the pulsatile electrical impedance
changes insitu. Since blood is a good conductor of electricity,
blood volume entering a body segment decreases the electrical
impedance and leaving a body segment increases the electrical
impedance respectively. Thus from the change in electrical impedance
it is possible to estimate the exact amount of blood entering
or leaving the body segment. BARC has added several innovations
to this principle by introducing simple, reliable and built-in
calibration; normalized impedance signal for easy interpretation;
real time processing for minimizing unwanted signals; segmental
assessments to know the approximate location of obstruction and
derivation of differential pulse arrival time to discriminate
between obstructions and narrowing. As a result of these innovations
it is possible to detect obstruction in arteries with an accuracy
of 96 per cent and obstructions in the veins with an accuracy
of 85 per cent which are far more satisfactory for a non-invasive
method.
Cardiac Output
Monitor
Cardiac output
is defined as the total volume of blood pumped by the heart in
one minute. Continuous monitoring of this parameter in critically
ill patients is very important in intensive care and intensive
cardiac care units. At a particular time instant, it is possible
to measure cardiac output by invasive methods like left ventriculography,
nuclear scintigraphy and dye/thermal dilution technique. However,
the application of these methods is limited as they can damage
the body and, furthermore, they cannot be repeated. Thus, to date,
there is no invasive or non-invasive method available for continuous
monitoring of cardiac output. Following the principle of impedance
plethysmography and Kubicek’s formula for estimation of stroke
volume, BARC has developed a small module for continuous monitoring
of cardiac output, non-invasively, which can be integrated with
the existing patient monitoring systems in the intensive care
units.
Medical Analyzer
This system has
been developed for analysing the periodic fluctuations in the
physiological paramenters in a living subject. These periodic
fluctuations are also named as variability. As we know that physiological
parameters like heart rate, respiration rate, stroke volume, cardiac
output, peripheral blood flow, systolic, diastolic and mean blood
pressures, body temperature, peristalsis, secretion of endocrinal
and salivary glands, glycogen-glucose conversion, motility of
large and small intestines and secretion of urine keep on fluctuating
as a function of time even in a resting subject. These fluctuations
are governed by the autonomous nervous system of the body. To
date, very few attempts have been made to objectively evaluate
the functioning of autonomous nervous system and use it for the
benefit of patients. BARC has taken a leap forward in introducing
respiration rate variability, cardiac output/peripheral blood
flow variability and stroke volume variability for the assessment
of autonomous nervous system and integrated these with already
existing heart rate variability in the form of Medical Analyzer.
This system records the impedance plethysmographic signal from
the chest or wrist of the patient for a period of 300 seconds
each. This signal is then analysed to obtain values of the heart
rate, respiration rate, stroke volume or peripheral blood flow
and cardiac output at intervals of one second for a total duration
of 300 seconds. This phase of the instrument is automatic and
stands to manual correction by the user. A plot of these values
as a function of time depicts the fluctuations in the parameter
in time domain which appear quite complex. Therefore, they are
transferred to frequency domain representation to highlight the
different periodicities of these time domain fluctuations.
The analyser
system has been carried out on 38 normal subjects, 31 patients
with hyperthyroidism, 23 patients with hypothyroidism, 19 patients
with AIDS, 16 patients with cirrhosis of liver and 9 patients
with diabetes at the Department of Medicine, J.J. Hospital, Mumbai.
(PIB Features)
 |
| Impedance Cardiovasograph system developed at BARC. The
data acquisition system is connected to right hand of the
control subject with the help of electrodes. It is controlled
by the personal computer and the final output is printed on
the ink jet printer. |
 |
| Medical Analyzer system developed at BARC. The data acquisition
is controlled by the PC, serially connected to the acquisition
unit. The variability analysis and transfer to database is
performed by the PC with the help of user-friendly software. |
*Head, Bio-Medical
Instrumentation Section, Electronics Division, BARC, Mumbai
