Bio Medical Instrument –
ER. FARUK BIN POYEN, Asst. Professor
DEPT. OF AEIE, UIT, BU, BURDWAN, WB, INDIA
Importance of Bio Medical Instrumentation
Basic Objectives of Biomedical Instrumentation
Anatomy and Physiology of Human Body
Physiological Systems of Human Body
Classification of Bio Medical Instruments
Sources of Biomedical Signals
Man – Instrumentation System
Constraints in Medical Instrumentation Design
Common Medical Measurements and Instruments
Medical instrumentation is a subdivision of biomedical engineering. It emphasizes the measurement of
all the variables in the body for the use of diagnosis and all the devices that perform therapy.
It is a cross-disciplinary field of study comprising
Biomedical Instrumentation is used to take measurements for
Biomedical instrumentation is generally classified into two major types:
Clinical Instrumentation is devoted to diagnosis, care and treatment of patients.
Research Instrumentation is used primarily in search for new knowledge pertaining to various systems
composing the human organism.
Importance of Bio Medical Instrumentation:
Studying of Biomedical Instrumentation helps in the following manners:
1. To understand mechanisms, efficiencies & physical changes of various subsystems of
2. To evolve an instrumentation system for diagnosis, therapy and supplementation of
3. To obtain qualitative & quantitative knowledge through different instruments which
can help for analysis of disorders, and further the Biomechanics of the cure process.
4. To understand Bio-Chemico-Electro – Thermo- Hydraulico- Pneumatico- Physico-
Magnato- Mechano – Dynamic actions and changes of various sub systems of the body
in normal states.
5. To understand above actions & changes in various sub systems of the body in the
abnormal states i.e. in Pathology.
6. To obtain qualitative & quantitative knowledge of what drug does to the body
(Pharmacodynamics) and what body does to the drug.
Basic Objectives of the Biomedical Instrumentation
Under mentioned are the principal objectives of a biomedical
1. Information Gathering: Instruments used to measure natural
phenomena to aid man in the quest of knowledge about himself.
2. Diagnosis: Measurements are made to help detect and correct
malfunction of the system being measured.
3. Evaluation: It is used to determine the ability of a system to meet its
4. Monitoring: It is used to monitor certain situation for continuous or
5. Control: It is used to automatically control the operation of a system
based on changes in multiple internal parameters.
Anatomy and Physiology:
The science of structure of the body is known as Anatomy and that of its functioning is
known as Physiology.
Anatomy is further classified as
1. Gross Anatomy: It deals with the study of structure of the organs with naked eyes on
2. Topographical Anatomy: It deals with the position of the organs in relation to each other.
3. Microscopic Anatomy (Histology): It is the study of the minute structures of the organs by
means of microscopy. Cytology is a special field where structure, function and
development of the cells are studied.
Physiology is classified into
1. Cell Physiology: The study of the functions of the cells.
2. Pathophysiology: It relates to the pathological (symptoms of diseases) functions of the
3. Circulatory Physiology: The study of blood circulation relating to the functioning of the
4. Respiratory Physiology: It deals with the functioning of the breathing organs.
Physiological Systems of the Human Body:
There are several systems working parallel to each other in our body. They are as
1. Cardiovascular System.
2. Respiratory System.
3. Nervous System.
4. Skeletal System.
5. Muscular System.
6. Digestive System.
7. Endocrine System.
8. Exocrine System.
9. Lymphatic System.
10. Urinary System.
11. Reproductive System.
Cardiovascular System: The circulatory system, also called the cardiovascular system
or the vascular system, is an organ system that permits blood to circulate and transport
nutrients (such as amino acids and electrolytes), oxygen, carbon dioxide, hormones,
and blood cells to and from the cells in the body to provide nourishment and help in
fighting diseases, stabilize temperature and pH, and maintain homeostasis.
Respiratory System: The respiratory system (called also respiratory apparatus,
ventilator system) is a biological system consisting of specific organs and structures
used for the process of respiration in an organism. The respiratory system is involved
in the intake and exchange of oxygen and carbon dioxide between an organism and the
environment. In air-breathing vertebrates like human beings, respiration takes place in
the respiratory organs called lungs.
Nervous System: The network of nerve cells and fibers which transmits nerve
impulses between parts of the body. It consists of two main parts, the central nervous
system (CNS) and the peripheral nervous system (PNS). The CNS contains the brain
and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the
long fibers or axons that connect the CNS to every other part of the body.
Skeletal System: The skeletal system includes all of the bones and joints in the body.
Each bone is a complex living organ that is made up of many cells, protein fibers, and
minerals. The skeleton acts as a scaffold by providing support and protection for the
soft tissues that make up the rest of the body. The skeletal system also provides
attachment points for muscles to allow movements at the joints.
Muscular System: The muscular system is an organ system consisting of skeletal,
smooth and cardiac muscles. It permits movement of the body, maintains posture, and
circulates blood throughout the body. The muscular system in vertebrates is controlled
through the nervous system, although some muscles (such as the cardiac muscle) can
be completely autonomous. Together with the skeletal system it forms the
musculoskeletal system, which is responsible for movement of the human body.
Digestive System: The digestive system is a group of organs working together to
convert food into energy and basic nutrients to feed the entire body. Food passes
through a long tube inside the body known as the alimentary canal or the
gastrointestinal tract (GI tract). The alimentary canal is made up of the oral cavity,
pharynx, esophagus, stomach, small intestines, and large intestines.
Endocrine System: The endocrine system includes all of the glands of the body and
the hormones produced by those glands. The glands are controlled directly by
stimulation from the nervous system as well as by chemical receptors in the blood and
hormones produced by other glands. By regulating the functions of organs in the body,
these glands help to maintain the body’s homeostasis.
Exocrine System: The exocrine system is an organ system consisting of the skin, hair,
nails, and exocrine glands. The skin is only a few millimeters thick yet is by far the
largest organ in the body. The average person’s skin weighs 10 pounds and has a
surface area of almost 20 square feet. Skin forms the body’s outer covering and forms a
barrier to protect the body from chemicals, disease, UV light, and physical damage.
Lymphatic System: The immune and lymphatic systems are two closely related organ
systems that share several organs and physiological functions. The immune system is
our body’s defense system against infectious pathogenic viruses, bacteria, and fungi as
well as parasitic animals and protists. The immune system works to keep these harmful
agents out of the body and attacks those that manage to enter.
Urinary System: The urinary system consists of the kidneys, ureters, urinary bladder,
and urethra. The kidneys filter the blood to remove wastes and produce urine. The
ureters, urinary bladder, and urethra together form the urinary tract, which acts as a
plumbing system to drain urine from the kidneys, store it, and then release it during
urination. Besides filtering and eliminating wastes from the body, the urinary system
also maintains the homeostasis of water, ions, pH, blood pressure, calcium and red
Reproductive System: The male reproductive system includes the scrotum, testes,
spermatic ducts, sex glands, and penis. These organs work together to produce sperm,
the male gamete, and the other components of semen. These organs also work together
to deliver semen out of the body and into the vagina where it can fertilize egg cells to
produce offspring. The female reproductive system includes the ovaries, fallopian
tubes, uterus, vagina, vulva, mammary glands and breasts. These organs are involved
in the production and transportation of gametes and the production of sex hormones.
The female reproductive system also facilitates the fertilization of ova by sperm and
supports the development of offspring during pregnancy and infancy.
Classification of Biomedical Instruments:
All biomedical instruments are categorized into different sectors of operations.
Following shows different instruments those are employed in different functional
BLOOD INSTRUMENTS HEART INSTRUMENT
Blood Pressure meter ECG
Blood PH meter Pace Maker
Blood flow meter Defibrillator
Blood cell counter Heart Lung Machine
Calorimeter Bed side Monitor
Spectra – Photometer Plethysmograph
Flame photometer Electronic stethoscope
Digital BP meter Phonocardiograph
Classification of Biomedical Instruments:
BRAIN INSTRUMENTS MUSCLE INSTRUMENTS
Tomograph Muscle Stimulator
KIDNEY INSTRUMENTS EAR INSTRUMENTS
Dialysis Instrument Audiometer
Lithotripsy Hearing aid
EYE INSTRUMENTS LUNG INSTRUMENTS
Aid for blind
Classification of Biomedical Instruments:
BODY INSTRUMENTS PHYSIOTHERAPHY INSTRUMENTS
Ultrasonography Diathermy, Short Wave
Thermograph Electro Sleeper
Radiograph Vibrator (Massage type)
EPF U.V. Lamph
Endoscope Microwave Diathermy
Biomedical instrumental measurements are divided in to two categories.
1. IN VIVO MEASURMENTS – In vivo measurements are made on or
within the living organism itself, e.g. a device inserted into the blood
stream to measure the pH of the blood directly.
2. IN VITRO MEASURMENTS – In vitro measurements are made
outside the body, even though it relates to the functions of the body,
e.g. measurements of pH of sample of blood that has been drawn from
Sources of Biomedical Signals:
Biometrics is the branch of science that deals with the measurement of physiological
variables and parameters.
Biomedical signals are used primarily for extracting information on biological system
1. Bioelectric Signals: These are unique to the biomedical systems. They are generated by
nerve cells and muscle cells. Their basic source is the cell membrane potential which under
certain conditions may be excited to generate an action potential. The electric field generated
by the action of many cell constitutes the bio-electric signal. The most common examples of
bioelectric signals are the ECG (electrocardiographic) and EEG (electroencephalographic)
2. Bio acoustic Signals: The measurement of acoustic signals created by many biomedical
phenomena provides information about the underlying phenomena. The examples of such
signals are; flow of blood in the heart, through the heart's valves and flow of air through the
upper and lower airways and in the lungs which generate typical acoustic signal.
3. Biomechanical Signals: These signals originate from some mechanical function of the
biological system. They include all types of motion and displacement signals, pressure and
flow signals. The movement of the chest wall in accordance with the respiratory activity is an
example of this type of signal.
Sources of Biomedical Signals:
4. Biochemical Signals: The signals which are obtained as a result of chemical measurements from
the living tissues or from samples analyzed in the laboratory. The examples are measurement of
partial pressure of carbon dioxide (pCO2), partial pressure of oxygen (pO2) and concentration of
various ions in the blood.
5. Bio magnetic Signals: Extremely weak magnetic fields are produced by various organs such as the
brain, heart and lungs. The measurement of these signals provides information which is not available
in other types of bio signals such bioelectric signals. A typical example is that of magneto
encephalograph MEG signals from the brain.
6. Bio – optic Signals: These signals are generated as result of optical functions of the biological
systems, occurring either naturally or induced by the measurement process. For example, blood
oxygenation may be estimated by measuring the transmitted/back scattered light from a tissue at
7. Bio – impedance Signals: The impedance of the tissue is a source of important information
concerning its composition, blood distribution and volume. The measurement of galvanic skin
resistance GSR is a typical example of this type of signal. The bio-impedance signal is also obtained
by injecting sinusoidal current in the tissue and measuring the voltage drop generated by the tissue
impedance. The measurement of respiration rate based on bio-impedance technique is an example of
this type of signals.
Sources of Biomedical Signals 18
Fig 1: Sources of Biomedical Signals
Man - Instrumentation System:
The overall system including both the human body and the
instrumentation required for its measurement is called the man –
instrumentation system. The set of instruments and equipment utilized in
the measurement of multiple characteristics plus the presentation of
these information in a readable and interpretable manner is called an
instrumentation system. In the man – instrumentation system, the human
body is treated as the black box (the unknown system) within which
several kinds of signals and systems are found, all interacting with each
Man - Instrumentation System:
Components of the Man – Instrumentation system:
1. The system components of Man – Instrumentation system are listed below.
2. The subject - The human being on which the measurements are to be carried out is
referred to as the subject under study or monitoring.
3. Stimulus: in many cases, an external triggering is required to initiate the measurement
process. This stimulus may be visual, auditory, tactile or direct electrical stimulation of
some part of the nervous system. This forms of the major components of the man –
4. Transducer: This is a device capable to converting the measured signal into a form of
energy interpretable and recording for further study and analysis.
Man - Instrumentation System:
5. Signal conditioning equipment: Most signals those are received from human body are
very light signals. Therefore these signals need amplification, modification so that they
can be interpreted properly.
6. Display Equipment: To be meaningful, the electrical output of the previous component
must be converted into a form that can be perceived by human senses. This requirement
makes the display equipment one of the vital components in man – instrumentation
7. Recording, Data – processing and Transmission Equipment: for later and further
analysis of the measured variables, the data needs to be recorded and transmitted over
locations making this module a very vital composition of the system.
8. Control Device: this forms the final component of the system giving the operators the
flexibility of automatic control of the stimulus. This is achieved by incorporating a
feedback loop in the system.
Man - Instrumentation System: 22
Fig 2: Man – Instrument System
Fig 3: Basic Medical Instrumentation System
Common Medical Measurands:
The following table shows few of the measurement parameters generally used in
medical instrumentation system along with its operational range and methods
employed in attaining the same.
TABLE I: Measurement Parameters with range
Measurement Type Range Frequency Hz Method
Blood Flow 1 to 300 mL/s 0 to 20 EM or US
Blood Pressure 0 to 400 mm Hg 0 to 50 Cuff or Strain Gage
Cardiac Output 4 to 25 L/min 0 to 20 Fick, dye dilution
ECG 0.5 to 4 mV 0.05 to 150 Skin Electrodes
EEG 5 to 300 μV 0.5 to 150 Scalp Electrodes
EMG 0.1 to 5 mV 0 to 10000 Needle Electrodes
Electroretinography 0 to 900 μV 0 to 50 Contact Lens Electrodes
pH 3 to 13 pH units 0 to 1 pH Electrodes
pCO2 40 to 100 mm Hg 0 to 2 pCO2 Electrodes
pO2 30 to 100 mm Hg 0 to 2 PO2 Electrodes
Pneumotachography 0 to 600 L/min 0 to 40 Pneumatochometer
Respiratory Rate 2 to 50 breaths/min 0.1 to 10 Impedance
Body Temperature 32 °C to 40 °C 0 to 0.1 Thermistor
Following are the set of few instruments that found application as a recording
3. Electro encephalography
10. Radio graph (X-ray)
Constraints in Medical Instrument Designs:
The signal to be measured inflicts limitations on how it should be acquired and
administered. Also the frequency range or signal strength is much lower than
conventional measuring parameters. .
Interference and cross talk between different organs and systems of the body may bring
down the accuracy and therefore diagnosis of the problem.
Placement of sensors is one major challenge in the scope of biomedical instruments as
perfect and most appropriate position is of primordial importance but it varies from
person to person.
Safety is the biggest concern in this field. The process of measurement must not
endanger the person on whom measurements are being made.
Operators’ expertise and constraints is a challenging aspect in this field.
Measurement variability is inherent at molecular, organ and body level. It is often
impossible to hold one variable constant while measuring the relationship between two
Introduction To Biomedical Equipment Technology; J. J. Carr, John Michael Brown
Basic Concepts of Medical Instrumentation: Application and Design; John G.
Biomedical Instrumentation And Measurements; Leslie, Cromwell.
Biomedical Instrumentation; R. S Khandpur and Raghbir Khandpur.
Introduction to Biomedical Instrumentation; Barbara Christe.
Biomedical Instrumentation; Dr. M Arumugam.
Introduction To Biomedical Instrumentation; Mandeep Singh
Principles of Medical Electronics and Biomedical Instrumentation; C. Raja Rao,
Sujoy K. Guha