EE09 L05 BIO- MEDICAL
ENGINEERING
MODULE-III
Part-II
Mohammed Anvar PK
Al-Ameen Engineering College
AP/ECE
Electroencephalography (EEG)
• Electroencephalography (EEG) is the recording of electrical activity of
brain.
• EEG measures voltage fluctuations resulting from ionic current flows
within the neurons of the brain.
• In clinical contexts, EEG refers to the recording of the brain's spontaneous
electrical activity over a short period of time, usually 20–40 minutes, as
recorded from multiple electrodes placed on the scalp
• EEG measurement are obtained from electrodes placed on the surface of
the scalp
• EEG potential represent a summation of the action potential of the neuron
in the brain
• The patterns obtained from scalp are actually the result of the graded
potentials on the dendrites of neuron in the cerebral cortex and other
parts of the brain
• EEG potentials have random-appearing waveforms with peak to peak
amplitude ranging less than 10µV to over 100µV and BW 1Hz to 100Hz
• Surface or subdermal needle electrode are used
• The ground reference electrode is often a metal clip on the earlobe
• Suitable electrolyte paste or jelly is used in conjunction with electrodes to
enhance the coupling of the ionic potentials to the input of the measuring
device
• Placement of electrode on the scalp is commonly by the requirements of the
measurement to be made
• In addition to the electrodes the measurement of EEG requires a readout or
recording device and sufficient amplification for the readout devices
• Most EEG provide the capability of simultaneously recording EEG signals from
several regions of the brain for each signal a complete channel of
instrumentation is required
• Thus EEG having 16 channels are available
• Because of low-level input signals EEG must have high quality
differential amplifiers with good common mode rejection
• The differential preamplifiers followed by a power amplifier to
drive the pen mechanism for each channel
• To reduce the effect of electrode resistance changes, the
input impedance of the EEG amplifier should be as high as
possible-modern EEG input impedance is greater than
10Mohm
• The readout in a clinical EEG is a multichannel pen recorder
with a pen for each channel
• Standard chart speed 30mm/sec but most EEG also provide
chart speed of 60mm/sec for improve the detail of higher
frequency signal
Wave group of normal cortex
• Alpha wave- 8 to 13Hz
– Recorded mainly at vision region
– Disappear when subject is sleep, change when subject change focus
• Beta wave- 14 to 30 Hz
– During mental activity
• Theta wave- 4 to 7Hz
– During emotional stress such as disappointment
• Delta wave- below 3.5Hz
– Occur in deep sleep and premature babies
• Gamma wave- 36 to 44Hz
– During sudden sensory stimuli
EMG measurements
• Electromyography (EMG) is a technique for evaluating and
recording the electrical activity produced by skeletal muscles
• Potential are measured at surface of body near muscle or
directly from by penetrating skin with needle electrodes
• Surface or needle electrodes pickup the potentials by
contracting muscle fibers
• The action potential from individual muscle fibers can be
recorded under special conditions
• The signal is a summation of all the action potential within
the range of electrodes.
• The overall strength of muscular contraction depends on the
number of fibers energized and the time of contraction
• The amplifier for EMG measurement must have high
gain, high input impedance and a differential input
with good common mode rejection
• EMG has an oscilloscope read out instead of graphic
pen recorder. The reason is that high frequency
response is required
• Most emg include an audio amplifier and loud
speaker in addition to oscilloscope to permit the
operator to hear the crackling sound of the EMG
• This audio presentation is especially helpful in the
placement of needle or wire electrodes into a
muscle
Nerve conduction velocity
• Nerve conduction velocity is an important aspect of nerve
conduction studies. It is the speed at which an
electrochemical impulse propagates down a neural pathway
• The conduction velocity in a peripheral nerve is measured by
stimulating a motor nerve at two points a known distance
apart
• Subtraction of shorter latency(duration) form the longer
latency gives the conduction time along the segment of nerve
between the stimulating electrode
• By measuring EMG down stream , a latency can be
determined from the time displayed on the oscilloscope
• Thus knowing the separation distance we can determine
conduction velocity of the nerve
• Conduction velocity, u=(D/(L1-L2))
Respiratory system
• Respiration is the exchange of gases in any biological
process
• Entire process of inhaling from atmosphere, transporting O2
to cells, removing Co2 from cells and exhausting the waste
products into atmosphere is called respiration
• Circulating blood is the medium by which oxygen is brought to
internal environment and by same mechanism Co2 is carried
out
• Exchange of gases between blood and external environment
take place in lungs and external expiration
Lung volume and capacities
• Pulmonary test are designed for determination of lung
volume of capacities
1.
2.
3.
4.
5.
6.
Tidal volume(TV)-Volume of air inhaled and exhaled in a single
breath
Inspired reserve volume(IRV)-the amount air that can be inhaled
beyond the tidal volume
Expiratory reserve volume(ERV)-amount of air that can be forcibly
exhaled beyond the tidal volume
Residual volume(RV)-amount of air remaining in lungs even after a
forceful maximal expiration
Vital capacity- maximal volume that can be exhaled after maximal
inhalation, vital capacity = RV+TV
Total lung capacity(TLC)-is amount of gas contained in lugs at end of
maximal inspiration, TLC=TV+RV+ERV+IRV
7.
8.
Inspiration capacity- maximum
amount of gas that can be
inspired after reaching the end
expiratory level, IC=TV+IRV
Functional residual volume
capacity- volume of gases
remaining in lungs at end of
expiration level,
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•
FRC=RV+ERV
FRC=TLC-IC
Measurements in respiratory system
Spirometry
• The changes in lung volume has been measured in
two
– To measure changes in the volume of gas space within the
body during breathing by using plethysmographic
techniques
– Spirometry-involves the measurement of gas passing
through the air way opening
• For the purpose of testing pulmonary functions frequently
implemented directly by electronically integrated output of a
flow meter placed at patients mouth( with nose blocked)
• Continuously gas passing through the airway opening and to
compute the volume it occupied with in the lungs this done
by the device –spirometer
• Spirometry- measurement of the changes in volume of lungs
for testing of pulmonary function
• The lung volume and capacities that can be obtained by
measuring the amount of gas inspired or expired under a
given set of conditions or during a specific interval can be
obtained by spirometer
• Spirometer composes of a movable bell inverted over a
chamber of water
• Inside the bell above the water lime is the gas that is to be
breathed
• the bell is balanced by a weight to maintain gas inside at
atmospheric pressure so that its height above water is
proportional to amount of gas in the bell
• Breathing tube connects the mouth of the patient with the
gas under the bell, the nose of patient is blocked
• Thus as patient breathes into the tube , the bell moves up
and down with each inspiration and expiration is proportion
to amount air breathed in and out
• A pen attached to balanced weight mechanism and writes on
paper attached to drum recorder called kymograph
• As the kymograph rotates the pen traces the breathing
pattern of patient
• Sometimes a rotational displacement sensor is fed to an OP
amp which can be connected electronic strip chart recorder
• Generally respiratory test are repeated two or three times
and maximum values are used to ensure that the patient
performed the test to the best of his ability
Pneumotachograph
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Also known as “differential pressure device”
Tube with fixed resistance
Contains a bundle of capillary tubes or fine meshes
This device utilizes the principle that air flowing through an
orifice produces a pressure difference across the orifice that is
a function of the velocity of air
• The orifice consist of a set of capillaries or a metal screen
• Since the cross section of the orifice is fixed, the pressure
difference can be calibrated to represent the flow
• Two pressure transducers or a differential pressure transducer
can be used to measure the pressure difference
Gas exchange and distribution
• Once air is in the lungs
oxygen and Co2 must be
exchanged between the air
and the blood in the lungs
and between the blood and
the cells in the body tissue
alveoli
Measurement of gaseous exchange
and diffusion
1. Chemical analysis method–
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in this a gas sample of approximately 0.5ml is introduced into a
reaction chamber by use of transfer pipet, at the upper end of the
reaction chamber capillary
an indicator droplet in this capillary allows the sample to be
balanced against a trapped volume of air in the thermobarometer
Absorbing fluid for Co2 and O2 can be transferred without causing
any change in the total volume of the system
The micrometer is adjusted so as to put mercury into the system in
place of gas being absorbed
The volume of absorbed gas is read from the micrometer calibration
2. Diffusion capacity using CO infrared analyzer–
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To determine the efficiency of perfusion of the lung by blood
and the diffusion of the gases
The most important tests are measure O2,Co2,pH and
bicarbonate in arterial blood
In this trying to measure the diffusion rate of oxygen from
alveoli into the blood. Assuming that alveoli have equal
concentration of oxygen actually this condition does not exist
bcz of unequal distribution of ventilation in the lung
Hence we use diffusion capacity or transfer factor used
rather than diffusion
Diffusion capacity in normal adult - 20 to 38 ml/min/mmHg it
varies with depth of inspiration, increases during excise and decreases
with low hemoglobin
•
In this method of measuring diffusion capacity involves the inhalation of low
concentrations of CO.
ml CO taken up/min
TF or diffusion capacity
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=
Pco in alveoli (mm/Hg)
For this measurement as well as for all methods requiring CO determination, a
CO analyzer or a gas chromatograph is used
The commonly used carbon monoxide analyzer utilizes an infrared energy source
, a beam chopper, sample and reference cells, plus a detector and amplifier
A milliammeter or a digital meter may be used for display
Two infrared beams are generated one directed through the sample and the
other through the reference
The CO gas mixture flowing through the sample cell absorbs more infrared
energy than does the reference gas
The two infrared beams are measured by a differential infrared detector
The out put is proportional to the amount of monitored gas in the sample cell,
the signal is amplified and presented to the output display meter or recorder
Measurement of gas distribution
• The distribution of oxygen from the lungs to the tissues and
Co2 from tissues to the lungs takes place in the blood
• Oxygen is carried by hemoglobin of the RBC, Co2 is carried
through chemical process in which Co2 and water combine to
produce carbonic acid, which is dissolved in the blood
• The amount of carbonic acid changes the pH of the blood
• In assessing the performance of the partial pressure
oxygen(Po2) and PCo2 in the blood , the percentage of oxygen in
the hemoglobin and the pH of blood are useful
Respiratory and therapy equipment
• When a patient is incapable of adequate ventilation by natural
process , mechanical assistance must be providedinstrumentation involved in providing mechanical assistance –
respiratory therapy
• Inhalators– the term generally indicates a device used to supply oxygen or some
other therapeutic gas to a patient
– Inhalators are used when a concentration of oxygen higher than the
air required
– The inhalator consists of a source of the therapeutic gas , equipment
for reducing pressure and controlling the flow of gas and a device for
administrating the gas
Ventilators and respirators
• Ventilators and respirators are used interchangeably to describe equipment
that may be employed continuously or intermittently to improve the
ventilation of the lungs and to supply humidity or aerosol medications to the
pulmonary trees
• The respirators and ventilators are classified as assistor – controllers and can
be operated any three different modes
1.
2.
3.
in assist mode inspiration is triggered by the patient. A pressure sensor
respond to the slight negative pressure that occurs each time the patient
attempt to inhale and triggers the apparatus to begin inflating the lungs.
In the control mode breathing is controlled by a timer set provide the
desired respiration rate. Controlled ventilation is required for patients who
are unable to breathe on their own
In the assist-control mode the apparatus is normally triggered by the
patients attempt to breathe as in the assist mode . However the patient
fails to breathe within a predetermined time , a timer automatically triggers
the device and inflated the lungs
• The various types of ventilators in clinical use
two types
• Pressure-cycled
• Positive pressure assistor-controller
Artificial heart valve
• An artificial heart valve is a device implanted in the heart of a
patient with valvular heart disease. When one of the four heart
valves malfunctions, the medical choice may be to replace the
natural valve with an artificial valve. This requires open-heart
surgery.
• Valves are integral to the normal physiological functioning of the
human heart.
• Natural heart valves are evolved to forms that perform the
functional requirement of inducing unidirectional blood flow
through the valve structure from one chamber of the heart to
another.
• Natural heart valves become dysfunctional for a variety of
pathological causes.
• Some pathologies may require complete surgical replacement of
the natural heart valve with a heart valve prosthesis
Heart lung machine
• A medical equipment that provides Cardiopulmonary
bypass, (temporary mechanical circulatory support) to
the stationary heart and lungs
• Heart and Lungs are made “functionless temporarily” ,
in order to perform surgeries
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CABG
Valve repair
Aneurysm
Septal Defects
Heart is Stopped
Blood circulated systemically
bypassing the heart
and lungs
Blood diverted through
tubes and is pumped
to maintain flow
Temperature regulation of blood
and gaseous exchange is done
Parts
• Five pump assemblies
• Venous Cannula
• Arterial Cannula - dual-stream aortic perfusion
catheter / meshed cannula
• Venous Reservoir
• Oxygenators
• Heat Exchangers
• Cardiotomy Reservoir and Field Suction
• Filters and Bubble Traps
• Tubing and Connectors
Centrifugal
Pumps
Roller
• Centrifugal pumps consist of plastic cones, which
when rotated rapidly, propel blood by centrifugal
force.
• Forward blood flow, varies with the speed of rotation
and the after load of the arterial line.
• Centrifugal blood pumps generate up to 900 mm Hg
of forward pressure, but only 400 to 500 mm Hg of
negative pressure. Hence, less gaseous micro emboli.
• Centrifugal pumps produce pulse less blood flow
• Roller pumps consist tubing, which is
compressed by two rollers 180° apart.
Forward flow is generated by roller
compression and flow rate depends upon the
diameter of the tubing, rate of rotation.
Roller Pump
Impeller Pump
Centrifugal Pump
Five pump assemblies :
• A centrifugal or roller head pump can be used in the
arterial position for outside body circulation of the blood.
• Left ventricular blood return is accomplished by roller
pump, drawing blood away from the heart.
• Surgical suction created by the roller pump removes
accumulated fluid from the general surgical field.
• The cardioplegia delivery pump.
• Emergency Backup of the arterial pump in case of
mechanical failure.
Venous Reservoirs
• Reservoirs may be rigid (hard) plastic canisters ("open"
types) or soft, collapsible plastic bags ("closed" types).
• The venous reservoir serves as volume reservoir
• Facilitates gravity drainage,
• Venous bubble trap present,
• Provides a convenient place to add drugs, fluids, or
blood, and adds storage capacity for the perfusion
system.
Oxygenators
Mebranous
Bubble
Membranous Oxygenators
• Imitate the natural lung by interspersing a thin
membrane of either micro porous
polypropylene or silicone rubber between the
gas and blood phases.
• With micro porous membranes, plasma-filled
pores prevent gas entering blood but facilitate
transfer of both oxygen and CO2.
• The most popular design uses sheaves of
hollow fibers connected to inlet and outlet
manifolds within a hard-shell jacket.
Bubble Oxygenators
• Venous blood drains directly into a chamber into which
oxygen is infused through a diffusion plate (sparger).
• The sparger produces thousands of small (approximately
36 µm) oxygen bubbles within blood.
• Gas exchange occurs across a thin film at the blood-gas
interface around each bubble
• Produce more particulate and gaseous microemboli are
more reactive to blood elements.
Heat Exchangers
• Control body temperature by heating or
cooling blood passing through the perfusion
circuit
• Temperature differences within the body and
perfusion circuit are limited to 5°C to 10°C to
prevent bubble emboli
Filters and Bubble Traps
• In the circuit, micro emboli are monitored by
arterial line ultrasound or monitoring screen
filtration pressure.
• Depth filters consist of porous foam, have a
large, wetted surface and remove micro
emboli by impaction and absorption
• Screen filters are usually made of woven
polyester or nylon thread.
Tubing
• Medical grade Polyvinyl Chloride (PVC) tubing
• It is flexible, compatible with blood, inert,
nontoxic, smooth, nonwettable, tough,
transparent, resistant to kinking and collapse,
• Can be heat sterilized
• The Duraflo II heparin coating ionically
attaches heparin to a quaternary ammonium
carrier (alkylbenzyl dimethyl - ammonium
chloride), which binds to plastic surfaces.
Perfusion Monitors and Sensors
• A low-level sensor with alarms on the venous
reservoir and a bubble detector on the arterial
line are desirable safety devices.
• Flow-through devices are available to
continuously measure blood gases,
hemoglobin/hematocrit , and some
electrolytes
• Temperatures of the water entering heat
exchangers
Sterilization :
• Ethylene dioxide is commonly used
• 4 hours of sterilization at 55°C or 18 hours at
22°C .
• Disadvantages of ethylene dioxide , are the
toxicity and explosive nature
• Disposable tubing ,reservoirs and oxygenator
• Steam sterilization as PVC can withstand heat
Hemodialysis
• In medicine, hemodialysis (also haemodialysis) is a method
that is used to achieve the extracorporeal removal of waste
products such as creatinine and urea and free water from the
blood when the kidneys are in a state of renal failure.
• Hemodialysis is one of three kidney failure therapies (the
other two being kidney transplant and peritoneal dialysis). An
alternative method for extracorporeal separation of blood
components such as plasma or cells is aphaeresis.
• Hemodialysis can be an outpatient or inpatient therapy.
Routine hemodialysis is conducted in a dialysis outpatient
facility, either a purpose built room in a hospital or a
dedicated, stand alone clinic
Cont…
•Blood is removed from the body and pumped by a
machine outside the body into a dialyzer (artificial
kidney)
•The dialyzer filters metabolic waste products from
the blood and then returns the purified blood to the
person
•The total amount of fluid returned can be adjusted
•A person typically undergoes hemodialysis at a
dialysis center
•Dialysate is the solution used by the dialyzer
Cont…
• Waste products (urea, creatinine,…ets) move
from blood into the dialysate by passive diffusion
along concentration gradient
• Diffusion rate depends on;
1.
The difference between solute concentrations in the blood and
dialysate
2.
Solute characteristics
3.
Dialysis filter composition
4.
Blood and dialysate flow rate
Lithotripsy
• Lithotripsy is a medical procedure involving the physical
destruction of hardened masses like kidney stones,
• Lithotripsy (also called ESWL- Extra-Corporeal Shock Wave
Lithotripsy) is a method is breaking up kidney stones in the
kidneys or tract ,using ultasound shock waves.
– Electromagnetic lithotripsy
– Electrohydraulic lithotripsy
– Endoscopic lithotripsy
– Extracorporeal shock wave lithotripsy
– Laser lithotripsy
Infants incubators
• Premature infants are babies born prior to the
normal 36 or 37 days, so they are unable to control
there temperature with the new environment and
also they could have some problems with their
respiratory systems so as the heart diseases.
• Heat is lost via evaporative, conductive, convective
and radiative means as shown in figure (1).
What is Infant Incubator
• Infant incubator is a biomedical device which
provides warmth, humidity, and oxygen all in a
controlled environment as needed by the new
born.
• It can be consider as therapy device.
Simple Block Diagram
Incubator Types
• Transport Incubator
• Intensive Care Incubator
• Radient Warmer
Temperature degree regulator method in
Incubator
• Linear Method : automatic control (ON or Off)
• Proportional control method
Proportional control method
Temp Control Signal
(Turn ON & Off for Heater)
Monitoring Respiration Rates
Parameters Control in Infant Incubator
• Temperature control.
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Air temperature mode
Skin temperature mode
• Humidity control.
• Humidity is defined as the percent of water evaporated molecules in the air.
• This is important for an infant baby, because if level of humidity was low the
baby's skin will be dry and cause a lot of health problems to him.
• Humidity probe:
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humidity transducer.
Humidity transducers principle is the capacitive changing types that mean any change
in humidity will cause a change in capacitive and the change in capacitive will be
translated to a change in voltage using bridge circuit.
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Oxygen control.
Alarms in Incubator
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Air flow alarm (fan stop alarm)
High temperature alarm
Power failure alarm
Probe alarm.
Set temperature alarm