Module VI APJAKTU EE372 Biomedical Instrumentation

1. Biomedical Instrumentation
Course Code:EE372
MODULE VI
1
Dr.LINSS T ALEX
ASSOCIATE PROFESSOR
DEPARTMENT OF EEE
MET’S SCHOOL OF ENGINEERING,MALA

3. Introduction to clinical laboratories:
Clinical labs are important in diseases diagnosis,
determination its severity and patient response to specific
treatment.
Diagnosis of any disease is first done by physical
examination by physician and confirmed by lab diagnosticexamination by physician and confirmed by lab diagnostic
tests.
Lab values are very important in determination of disease
severity, drug doses and in follow up.

4. Introduction
The sections of clinical laboratory are:
Clinical pathology
Hematology
Clinical biochemistry
Clinical microbiologyClinical microbiology
Serology
Blood bank
Histology and cytology

5. Introduction
Clinical biochemistry:
It deals with the applications of biochemistry laboratory to
find out the cause of a disease.
Types of samples that are used in testing:Types of samples that are used in testing:
Body fluids: blood, serum, plasma, urine, cerebrospinal fluid
(CSF), feces, and other body fluids or tissues.

6. Biochemical tests in clinical medicine
Lipid profile
Diabetic profile
Kidney profile
Liver profile
Bone profileBone profile
Electrolyte profile

7. Lab request and lab report forms
Lab request form: it fills computerize or paper filled by the doctor then
send it to the lab. The lab request contains a list of tests to be
performed on specimen of patient. Each lab has its specific request; for
example, chemistry request, hematology request… etc.
Lab report form: it contains the result of patient.
Laboratory work flow cycle:
The flow cycle includes the entire steps of laboratory test, starting fromThe flow cycle includes the entire steps of laboratory test, starting from
test ordering by a doctor until reporting the results.
Three phases of laboratory testing:
Pre-analytical: test ordering, specimen collection, transport and
processing
Analytical-testing
Post-analytical: testing results transmission, interpretation, follow-up,
retesting.

8. Disposable syringes Vacationer systems Disposable lancets
Gauze pads absorbent cotton Tourniquet
Phlebotomy or blood collection:Phlebotomy or blood collection:
The term phlebotomy refers to blood
draw from a vein, artery, or the
capillary bed for lab analysis or blood
transfusion.
Phlebotomy
Alcohol swap Plastic bandage Waste container

9. Usually vein is used to collect blood
by veinpuncture procedure.
In adults: most venipuncture
procedure use arm vein.
On arm, one of three arm veins is
used: median cubital vein "located
on the middle", cephalic vein or
basilic vein "located on both sides".
Median cubital vein is the best
choice because it has good blood
flow than cephalic and basilica which
Selecting vein site
flow than cephalic and basilica which
has slower blood flow.
However if veinpuncture procedure
is unsuccessful in median capital;
cephalic or basilica is used.
Artery blood is rarely used in special
cases as when blood gases, pH,
PCO2, PO2 and bicarbonate is
requested. It is usually performed
by physicians.

10. Preparation of Blood Sample
One of three different specimens may be used:
• whole blood
• serum
• plasma
First: Whole-blood specimen:First: Whole-blood specimen:
It must be analyzed within limited time (why?)
– Over time, cells will lyse in whole-blood which will change
the conc. of some analytes as potassium, phosphate and
lactate dehydrogenase.
– Some cellular metabolic processes will continue which will
alter analytes conc. like glucose and lactate.

11. Serum
Second Serum:
Difference between Serum and plasma:
• Serum is the same as plasma except it doesn't contain
clotting factors (as fibrin).
• Plasma contains all clotting factors.• Plasma contains all clotting factors.
• So, serum and plasma all has the same contents of
electrolytes, enzymes proteins, hormones except clotting
factors
• Serum is mainly use in chemistry lab & serology.

12. Procedure of Serum preparation
• Draw blood from patient. Select vacutainer with no
anticoagulant.
• Allow to stand for 20-30min for clot formation.
• Centrifuge the sample to speed separation and affect a
greater packing of cells. Clot and cells will separate fromgreater packing of cells. Clot and cells will separate from
clean serum and settle to the bottom of the vessel.
• The supernatant is the serum which can be now collected
by
• Dropper or pipette for testing purposes or stored (-20°C to -
80°C) for subsequent analysis or use.

13. Plasma
Third Plasma:
• The tube will have anti-coagulation
• After centrifugation the blood sample got separated into
three layers

14. Procedure of plasma preparation
• Draw blood from patient. Select vacutainer with an appropriate
anticoagulant.
• Mix well with anticoagulant.
• Allow to stand for 10min.
• Centrifuge the sample to speed separation and affect a greater• Centrifuge the sample to speed separation and affect a greater
packing of cells.
• The supernatant is the plasma which can be now collected for testing
• Purposes or stored (-20°C to -80°C) for subsequent analysis or use.

15. In the lab
Specimen rejection criteria:
• Specimen improperly labeled or unlabeled
• Specimen improperly collected or preserved
• Specimen submitted without properly completed request
formform
• Hemolyzed sample (show tubes)

16. Hemolysis
Hemolysis :
• It means liberation of hemoglobin due to rupture of RBCs.
• Due to hemolysis plasma or serum appears pink to red color.
• It causes elevation in: K+, Ca2+, phosphate, SGOT, SLDH and acid
phosphatase.
• Hemolysis is occurred due to sampling, transporting and storage (too hot or
too cold).
• According to the degree of hemolysis it is classified as H+, H++ and H+++.
H+ may be accepted for some tests that are not affected by RBCs contentsH+ may be accepted for some tests that are not affected by RBCs contents
as glucose and lactate, H++ and H+++ not acceptable for any test.
Changes in the serum color indicate one of the following:
• Hemolyzed: serum appears pink to red due to rupture of RBCs
• Icteric: serum appears yellow due to high bilirubin.
• Lipemic: serum appears milky or turbid due to high lipid.

17. Blood collection tubes:

18. Blood collection tubes:
Two major types of blood collecting tubes:
• Serum separating tubes (SST)
• Plasma separating tubes (PST)

19. TESTS ON BLOOD CELLSTESTS ON BLOOD CELLS
• When whole blood is centrifuged, the blood cells sediment
and form a packed column at the bottom of the test tube.
• Most of this column consists of the red blood cells, with
the other cells forming a thin, buffy layer on top of the red
cells.
• The volume of the packed red cells is called the hematocrit
• It is expressed as a percentage of the total blood volume.
• If the number of (red) blood cells per cubic millimeter of
blood is known, this number and the hematocrit can be
used to calculate the mean cell volume (MCV).

20. • As stated above, the active component in the red
blood cells is the hemoglobin, the concentration of
which is expressed in grams/ 100 ml.
• From the hemoglobin, the hematocrit and the
blood cell count, the mean cell hemoglobin (MCH)
(in picograms) and the mean cell hemoglobin(in picograms) and the mean cell hemoglobin
concentration (MCHC) (in percent) can be
calculated.

21. • The hematocrit can be determined by aspirating a
blood sample into a capillary tube and closing one
end of the tube with a plastic sealing material.
• The tube is then spun for 3 to 5 minutes in a special
high-speed centrifuge to separate the blood cells from
the plasma.
• Because the capillary tube has a uniform diameter,
the blood and cell volumes can be compared bythe blood and cell volumes can be compared by
measuring the lengths of the columns.
• This is usually done with a simple nomogram, as
shown in Figure 13.1.
• When lined up with the length of the blood column,
the nomogram allows the direct reading of the
hematocrit.

23. • The red blood cells have a much higher electrical
resistivity than the blood plasma in which they are
suspended, and so the resistivity of the blood
shows a high correlation with the hematocrit.
• This factor provides an alternative method of
determining the hematocrit that is obviously more
adaptable to automation than the centrifugaladaptable to automation than the centrifugal
sedimentation method.

24. • The hemoglobin concentration can be determined
by lysing the red blood cells (destroying their
membranes) to release the hemoglobin and
chemically converting the hemoglobin into another
colored compound (acid hematin or
cyanmethemoglobin).
• Unlike that of the hemoglobin, the color• Unlike that of the hemoglobin, the color
concentration of these components does not
depend on the oxygenation of the blood.
• Following the reaction, the concentration of the
new component can be determined by
colorimetry.

25. • Manual blood cell counts are performed by using a
microscope.
• Here the blood is first diluted 1:100 or 1:200 for
counting red blood cells (RBC) and 1:10 or 1:20 for
white blood cell count (WBC).
• For counting WBC, a diluent is used that dissolves• For counting WBC, a diluent is used that dissolves
the RBCs, whereas for counting RBCs, an isotonic
diluent preserves these cells.
• The diluted blood is then brought into a counting
chamber 0. 1 mm deep, which is divided by marking
lines into a number of squares.

26. • When magnified about 500 times, the cells in a
certain number of squares can be counted.
• This rather time-consuming method is still used
quite frequently when a differential count is
required for which the WBCs are counted,
according to their distribution, into a number of
different subgroups.different subgroups.
• An automated differential blood cell analyzer uses
differential staining methods to discriminate
between the various types of white blood cells.

27. • Today simple RBC and WBC counts are normally performed by
automatic or semiautomatic blood cell counters.
• The most commonly used devices of this kind are based on
the conductivity (Coulter) method, which makes use of the
fact that blood cells have a much lower electrical conductivity
than the solution in which they are suspended.
• Such a counter (Figure 13.2) contains a beaker with the
diluted blood into which a closed glass tube with a very small
orifice (1) is placed.orifice (1) is placed.
• The conductance between the solution in the glass tube and
the solution in the beaker is measured with two electrodes
(2).
• This conductance is mainly determined by the diameter of
the orifice, in which the current density reaches its maximum.
• The glass tube is connected to a suction pump through a U-
tube filled with mercury (5).

29. • The negative pressure generated by the pump
causes a flow of the solution from the beaker
through the orifice into the glass tube.
• Each time a blood cell is swept through the orifice,
it temporarily blocks part of the electrical current
path and causes a drop in the conductance
measured between the electrodes (2).measured between the electrodes (2).
• The result is a pulse at the output of the
conductance meter, the amplitude of which is
proportional to the volume of the cell.
• A threshold circuit lets only those pulses pass that
exceed a certain amplitude.

30. • The pulses that pass this circuit are fed to a pulse counter
through a pulse gate.
• The gate opens when the mercury column reaches a first
contact (3) and closes when it reaches the second contact (4),
thus counting the number of cells contained in a given
volume of the solution passing through the orifice.
• A count is completed in less than 20 seconds.
• With counts of up to 100,000, the result is statistically
accurate.
• Great care must be taken, however, to keep the aperture from• Great care must be taken, however, to keep the aperture from
clogging.
• Counters based on this principle are available with varying
degrees of automation.
• The most advanced device of this type (shown in Figure 13.3)
accepts a new blood sample every 20 seconds, performs the
dilutions automatically, and determines not only the WBC and
RBC counts but also the hematocrit and the hemoglobin
concentration.

32. • From these measurements, the mean cell volume, the
mean cell hematocrit, and the mean cell hematocrit
concentration are calculated and all results are printed
out on a preprinted report form.
• A second type of blood cell counter uses the principle
of the dark-field microscope (Figure 13.4).
• The diluted blood flows through a thin cuvette (4). The
cuvette is illuminated by a cone-shaped light beamcuvette is illuminated by a cone-shaped light beam
obtained from a lamp (1) through a ring aperture (3)
and an optical system (2).
• The cuvette is imaged on the cathode of a phototube
(7) by means of a lens (5) and an aperture (6).
• Normally no light reaches the phototube until a blood
cell passes through the cuvette and reflects a flash of
light on the phototube.

34. CHEMICAL TESTSCHEMICAL TESTS
• Blood serum is a complex fluid that contains numerous
substances in solution.
• The determination of the concentration of these
substances is performed by specialized chemical
techniques.
• Although there are usually several different methods
by which any particular analysis can be performed,by which any particular analysis can be performed,
most tests used are based on a chemical color reaction
followed by a colorimetric determination of the
concentration.
• This principle makes use of the fact that many chemical
compounds in solution appear colored, with the
saturation of the color depending on the concentration
of the compound.

35. • For instance, a solution that appears yellow
when being held against a white background
actually absorbs the blue component of the
white light and lets only the remainder—namely,
yellow light—through.
• The way in which this light absorption can be
used to determine the concentration of theused to determine the concentration of the
substance is shown in Figure 13.5.

37. • In Figure 13.5(a) it is assumed that a solution of
concentration C is placed in a cuvette with a length of
the light path, L.
• Light of an appropriate color or wavelength is
obtained from a lamp through filter F.
• The light that enters the cuvette has a certain
intensity, Io.
• With part of the light being absorbed in the solution,• With part of the light being absorbed in the solution,
the light leaving the cuvette has a lower intensity I1.
• One way of expressing this relation is to give the
transmittance, T,
• of the solution in the cuvette as the percentage of
light that is transmitted:

38. • If a second cuvette with the same solution were
brought into the light path behind the first cuvette,
only a similar portion of the light entering this
cuvette would be transmitted.
• The light intensity 12 behind the second cuvette is

39. • The light transmitted through successive cuvettes
decreases in the same manner (multiplicatively).
• For this reason, it is advantageous to express
transmittance as a logarithmic measure (in the
same way as expressing electronic gains and losses
in decibels).
• This measure is the absorbance or optical density,
A.

40. • The total absorbance of the two cuvettes in Figure 13.5(a)
is, therefore, the sum of the individual absorbances.
• The amount of the light absorbed depends only on the
number of molecules of the absorbing substance that can
interact with the light.
• If, instead of two cuvetttes, each with path length L, one
cuvette with path length 2L, were used [Figure 13.5(b)], thecuvette with path length 2L, were used [Figure 13.5(b)], the
absorbance would be the same.
• The absorbance is also the same if the cuvette has a path
length L, but the concentration of the solution were
doubled [Figure 13.5(c)].
• This relation can be expressed by the equation:
A = aCL (Beer's law)

41. • where L = path length of the cuvette
• C = concentration of the absorbing substance
• a = absorbtivity, a factor that depends on the absorbing
substance and the optical wavelength at which the
measurement is performed.
• The absorbtivity can be obtained by measuring the
absorption of a solution with known concentration,absorption of a solution with known concentration,
called a standard.
• If As is the absorption of the standard, Au is the
absorption of an unknown solution, and Q the
concentration of the standard, then the concentration
of the unknown is

42. • Corrections may have to be applied for light losses
due to reflections at the cuvette or absorption by
the solvent.
• Figure 13.6 shows the principle of a colorimeter or
filter-photometer used for measuring transmittance
and absorbance of solutions.
• A filter F selects a suitable wavelength range from• A filter F selects a suitable wavelength range from
the light of a lamp.
• This light falls on two photoelectric (selenium) cells:
a reference cell CR and a sample cell CS.
• Without a sample, the output of both cells is the
same.

43. • When a sample is placed in the light path for the
sample cell, its output is reduced and the output of
CR has to be divided by a potentiometer P until a
galvanometer (G) shows a balance.
• The potentiometer can be calibrated in
transmittance or absorbance units over a range of 1transmittance or absorbance units over a range of 1
to 100 percent transmittance, corresponding to 2 to
absorbance units.

45. • Other colorimeters, instead of using the
potentiometric method, use a meter calibrated
directly in transmittance units (a linear scale) and in
absorbance.
• If a standard with a known concentration of a
certain substance is used as a reference, the scale
can be calibrated directly in concentration units forcan be calibrated directly in concentration units for
this substance.

46. • In order to use the colorimeter to determine the
concentration of a substance in a sample, a suitable
method for obtaining a colored derivative from the
substance is necessary.
• Thus, a chemical reaction that is unique for the
substance to be tested and that does not cause
interference by other substances which may be present
in the sample must be found.in the sample must be found.
• The reaction may require several steps of adding
reagents and incubating the sample at elevated
temperatures until the reaction is completed.
• Most reactions require that the protein first be
removed from the plasma by adding a precipitating
reagent and filtering the sample.

47. • In most tests, an excess of the reagents is added
and the incubation is continued until the end point
of the reaction is reached (i.e., until all of the
substance has been converted into its colored
derivative).
• In kinetic analysis methods, the transmittance is
measured several times at fixed time intervalsmeasured several times at fixed time intervals
while the chemical reaction continues.
• The concentration of the substance of interest
then can be calculated from the rate of change of
the absorbance.

49. • The most commonly required tests for blood
samples are listed in Table 13.1.
• This table also shows the units in which the test
results are expressed and the normal range of
concentration for each test.
• Most of these tests can be performed by color
reaction even though, in most cases, several
different methods have been described that candifferent methods have been described that can
often be used alternately.
• For the measurement of sodium and potassium,
however, a different property is utilized, one that
causes a normally colorless flame to appear yellow
(sodium) or violet (potassium) when their solutions
are aspirated into the flame.

50. • This characteristic is used in the flame photometer
(Figure 13.8) to measure the sodium or potassium
concentration in samples.
• The sample is aspirated into a gas flame that burns in a
chimney.
• As a reference, a known amount of a lithium salt is
added to the sample, thus causing a red flame.
• Filters are used to separate the red light produced by• Filters are used to separate the red light produced by
the lithium from the yellow or violet light emitted by
the sodium or potassium.
• As in the colorimeter, the output from the sample cell
CS is compared with a fraction of the output from a
reference cell CR.
• The balance potentiometer P is calibrated directly in
units of sodium or potassium concentration.

51. • For the determination of chlorides, a special
instrument (chloridimeter) is sometimes used that
is based on an electrochemical (coulometric)
method.
• For this test, the chloride is converted into silver
chloride with the help of an electrode made of
silver wire.silver wire.
• By an electroplating process with a constant
current, the silver chloride is percipitated.

54. • When all the chloride has been used up, the
potential across the cell changes abruptly and the
change is used to stop an electric timer, which is
calibrated directly in chloride concentration.
• The simple colorimeter (or filter-photometer)
shown in Figures 13.6 and 13.7 has a sophisticated
relative, the spectrophotometer shown in Figurerelative, the spectrophotometer shown in Figure
13.9.
• In this device the simple selection filter of the
colorimeter is replaced by a monochromator.
• A monochromator uses a diffraction grating G (or a
prism) to disperse light from a lamp that falls
through an entrance slit S1 into its spectral
components.

55. • An exit slit S2 selects a narrow band of the spectrum,
which is used to measure the absorption of a sample
in cuvette C.
• The narrower the exit slit, the narrower the
bandwidth of the light, but also the smaller its
intensity.
• A sensitive photodetector D (often a
photomultiplier) is therefore required, together withphotomultiplier) is therefore required, together with
an amplifier and a meter I, which is calibrated in
units of transmittance or absorbance.
• The wavelength of the light can be changed by
rotating the grating.
• A mirror M folds the light path to reduce the size of
the instrument.

56. • The spectrophotometer allows the determination
of the absorption of samples at various
wavelengths.
• The light output of the lamp, however, as well as
the sensitivity of the photodetector and the light
absorption of the cuvette and solvent, varies whenabsorption of the cuvette and solvent, varies when
the wavelength is changed.
• This situation requires that, for each wavelength
setting, the density reading be set to zero, with the
sample being replaced by a blank cuvette, usually
filled with the same solvent as used for the
sample.

57. • In double-beam spectrophotometers this
procedure is done automatically by switching the
beam between a sample light path and a reference
light path, generally with a mechanical shutter or
rotating mirror.
• By using a computing circuit, the readings from
both paths are compared and only the ratio of theboth paths are compared and only the ratio of the
absorbances (or the difference of the densities) is
indicated.

58. • Certain chemicals, when illuminated by light with a
short wavelength in the ultraviolet (UV) range, emit
light with a longer wavelength.
• This phenomenon is called fluorescence.
• Fluorescence can be used to determine the
concentration of such chemicals using a
fluorometer, which, like the photometer, can befluorometer, which, like the photometer, can be
either a filter-fluorometer or a spectro fluorometer,
depending on whether filters or monochromators
are used to select the excitation and emission
wavelengths.

59. Medical Instrument Electrical SafetyMedical Instrument Electrical Safety
Significance of safety
• Thousands of devices related patient injuries in
every year.
• Even a single harmful event can lead to significant
damage in terms of reputation and legal action.damage in terms of reputation and legal action.
• Different level of protection required as compared
to household equipment.
• Minimum performance standards introduced in
1980s –relatively new practice.

60. Physiological Effects ofPhysiological Effects of Electric CurrentElectric Current
• For a physiological effect the body must become part of
an electrical circuit
• Three phenomena occur when electric current flows
1. Electrical stimulation of excitable tissue (muscle, nerve)
2. Resistive heating of tissue2. Resistive heating of tissue
3. Electrochemical burns
• Further consideration are based on the following parameters
• Human body with contact to el. circuit at left and right hand
• Body weight: 70 kg
• Applied current time: 1 s to 3 s
• Current frequency: 60 Hz

62. Threshold of Perception
• Current density is just large enough to excite nerve
endings in the skin
• Subject feels tingling sensation
• Lowes values with moistered hands (decreases• Lowes values with moistered hands (decreases
contact resistance)
• 0.5 mA at 60 Hz
• 2 mA to 10 mA DC
• The subject might feel a slight warming

63. Let-go Current
• The let-go current is defined as the maximal current
at which the subject can withdraw voluntarily
• For higher current nerves and muscles are
vigorously stimulatedvigorously stimulated
• Involuntary contraction or reflex withdrawals may
cause secondary physical injuries (falling off the
ladder)
• The minimal threshold for the let-go current is 6 mA

64. Respiratory Paralysis, Pain, Fatigue
• Higher current causes involuntary contraction of
muscles and stimulation of nerves what can lead to
pain and cause fatigue
Example: stimulation of respiratory muscles lead to
involuntary contraction with the result ofinvoluntary contraction with the result of
asphyxiation if current is not interrupted

65. Ventricular Fibrillation
• The heart is especially susceptible to electric
current.
• Just 75 mA to 400 mA (AC) can rapidly disorganize
the cardiac rhythm and death occurs within
minutesminutes
• Only a brief high-current pulse from a defibrillator
can depolarize all the cells of the heart muscle
simultaneously
• Within the U.S. occur approximately 1,000 death
per year due to cord connected appliances

66. Sustained Myocardial Contraction
• When current is high enough to stimulate the
entire heart muscle, it stops beating
• Usually the heart-beat ensues when the
current is interruptedcurrent is interrupted
• Minimal currents range from 1 A to 6 A (AC),
like used in defibrillators

67. Burns and Physical Injury
• Resistive heating cause burns
• Current can puncture the skin
• Brain and nerve tissue may lose all functional
excitabilityexcitability
• Simultaneously stimulated muscles may contract
strong enough to pull the attachment away from
the bone or bread the bone

69. Susceptibility Parameters IntroductionSusceptibility Parameters Introduction
The current needed to produce each effect depends
on these parameters:-
• Threshold of Perception and Let-Go Variability
• Frequency
• Duration• Duration
• Body Weight (and gender)
• Points of Entry
Macroshock
Microshock

70. Threshold and Let-Go Variability
• For men the mean value for the threshold of
perception is 1.1mA;for women, the estimated mean
is 0.7mA.
• The minimal threshold of perception is 500µA.
• When the current was applied to ECG gel electrodes,• When the current was applied to ECG gel electrodes,
the threshold of perception averages 83µA with a
range of 30 to 200µA
• Let-go current for men is 16mA and 10.5mA for
women.
• The minimal threshold let-go current is 9.5mA for
men and 6mA for women

71. Variability of threshold and Let-go current
Figure : Distributions of
perception thresholds
and let-go currents
These data depend on
surface area of contactsurface area of contact
(moistened hand
grasping AWG No. 8
copper wire)

72. Frequency
Let-go current versus frequency
Minimal let-go currents occur for
commercial power-line frequencies (50
Hz to 60 Hz) For frequencies below 10
Hz let-go current rises again (muscle
can relax)
Figure : Let-go current versus frequency
Percentile values indicate variability of
let-go current among individuals. Let-go
currents for women are about two-thirds
the values for men.

73. Duration
• Geddes and Baker (1989) presented the
excitation behaviour of myocardial cells by a
lumped parallel RC circuit that represents the
resistance and capacitance of the cell membrane.
• This model determines the cell excitation• This model determines the cell excitation
thresholds that exceed about 20 mV for varying
rectangular pulse duration d by assigning the
current Ir and cell membrane time constant
τ=RC.
• The strength-duration equation

74. • For a short duration: Stimulation current I
d is inversely related to the pulse duration
d (Figure below)
Figure: Normalized
analytical strength–
duration curve for
current I, charge Q,
and energy U. The xand energy U. The x
axis shows the
normalized duration
of d/τ

75. Body weight
• Several studies (animals) show a
clear dependency of the
fibrillating current to the body
weight (Figure beside) 50 mA
rms for 6kg dogs to 130 mA rms
for 24 kg dogsfor 24 kg dogs
• Figure : Fibrillation current
versus shock duration.
Thresholds for ventricular
fibrillation in animals for 60 Hz
ac current. Duration of current
(0.2 to 5 s) and weight of animal
body were varied.

76. Points of Entry
• Macroshock: only a small fraction of the total current flows through
the heart. Magnitude to harm the heart is far greater
• Microshock: all the current applied flows through the heart
Figure: Effect of entry points on
current distribution (a)current distribution (a)
Macroshock, externally applied
current spreads throughout the
body, (b) Microshock, all the
current applied through an
intracardiac catheter flows through
the heart.

77. Shock Hazards from Electrical EquipmentShock Hazards from Electrical EquipmentShock Hazards from Electrical EquipmentShock Hazards from Electrical Equipment

78. Macroshock Hazards
Macroshock = current spreads through the body
Two factors reduce danger in case of an electric shock
1. High skin resistance (15kohm to 1 Mohm at 1 cm2)
2. Spatial distribution
Many medical devices
• Reduce the skin resistance with ionic gel (good electrode contact), or
•Bypass the natural protection by bypassing the skin (thermometer in the
mouth intravenous catheters, etc.)
• Many fluids conduct electricity (blood, urine, intravenous solution,etc.)
Result
• Patients in medical-care facilities are much more susceptible to
macroshocks

79. Macroshock Hazards Protection
• Ground fault with short circuit to a metal chassis
a. not grounded chassis ->macroshock
b. grounded chassis-> safe

80. Figure : Macroshock due to a ground fault from
hot line to equipment cases for (a)
ungrounded cases and (b) grounded chassis.

81. Microshock Hazards
Microshock = all current flows through the heart
• Microshock accidents generally result from
• leakage-currents in line-operated equipment
• differences in voltage between grounded
conductive surfaces due to large currents in theconductive surfaces due to large currents in the
grounding system
• Microshock currents can flow either into or out of the
electric connection to the heart
Result
• Patient is only in danger of microshock if there is
some electric connection to the heart

82. Microshock Hazards Protection
• Leakage-current flows
a. through the ground wire – no microshock occurs
b. through the patient if he touches the chassis and
has a grounded catheter etc.
c. through the patient if he is touching ground and
has a connected catheter etc.

83. Figure : Microshock leakage-
current pathways. Assume 100
μA of leakage current from the
power line to the instrument
chassis,
(a) Intact ground, and 99.8 μA(a) Intact ground, and 99.8 μA
flows through the ground,
(b) Broken ground, and 100
μA flows through the
heart,
(c) Broken ground, and 100
μA flows through the
heart in the opposite
direction.

84. METHOD OF ACCIDENT PREVENTIONMETHOD OF ACCIDENT PREVENTIONMETHOD OF ACCIDENT PREVENTIONMETHOD OF ACCIDENT PREVENTION

85. Basic Approaches to Protection against Shock
There are two fundamental methods of protecting patients
against shock
1. Complete isolation and insulation from all grounded objects
and all sources of electric current
2. Same potential of all conducting surfaces within reach of the
patients
2. Same potential of all conducting surfaces within reach of the
patients
• Neither approach can be fully achieved in most practical
environments, so some combination must usually suffice
• Protection must include patient, applicants and third party
persons

86. Protection: Power Distribution Grounding System
• Low-resistance grounding
system carry currents up to
circuit-breaker ratings by
keeping all conductive
surfaces on the same
potential
•Patient-equipment grounding
pointpoint
• Reference grounding point
• Connections for other
patient-equipment
Figure 14.14 Grounding system All the receptacle
grounds and conductive surfaces in the vicinity of
the patient are connected to the patient-
equipment grounding point. Each patient
equipment grounding point is connected to the
reference grounding point that makes a single
connection to the building ground.

87. Protection: Power Distribution Ground-
Fault Circuit Interrupter (GFCI)
• Ground-fault circuit interrupters disconnect the source
power when a ground fault greater than about 6 mA
occurs
• GFCI senses differences in the in- an outgoing current• GFCI senses differences in the in- an outgoing current
• Most GFCI use differential transformer and solid-state
circuitry
• Most GFCI are protectors against macroshocks as they
are usually not as sensitive as 10 µA or the medical
equipment has a fault current greater than that

88. Protection: Equipment Design
Introduction
Most failures of equipment ground occur at the ground contact or in the
plug and cable
• Moulded plugs should be avoided because of invisible breaks
• Strain-relief devices are recommended
• No use of three-prong-to-two-prong adapters (cheater adapters)
Reduction of leakage currentReduction of leakage current
• Special use of low-leakage power cords
• Capacitance-minimized design (special layout-design and usage of
insulation)
• Maximized impedance from patient leads to hot conductors and from
patient leads to chassis ground

89. Double-Insulated equipment
• Interconnection of all conducting surfaces
• Separate layer of insulation to prevent contact
with conductive surfaces (e.g. non conductive
chassis, switch levers, knobs, etc.)
• Operation at low voltages
• Electrical isolation

90. Telemedicine
Telemedicine is the remote communication of
information to facilitate clinical care.

91. Exchange of Information at a Distance
• Voice
• Image
• Video
• Graphics• Graphics
• Elements of Medical Records
• Commands to a surgical robot

93. Technologies Involved
• Medical Instrumentation
Sensing Bio-medical Signals,
Medical Imaging, Measurement of Physical
Parameters e.g. Body Temperature, Pressure etc.
• Telecommunication Technology• Telecommunication Technology
Trans-receiver on different communication
channels and network such as, on wired
network, wireless medium etc.
• Information Technology
Information representation, storage,
retrieval, processing, and presentation.

94. Early systems
• 1920 (USA): Transmission of ECGs and EEGs on
ordinary telephone lines.
• 1920 (USA): Medical advice services for sailors based
upon Morse code and voice radio.upon Morse code and voice radio.
• 1950’s (USA): Telepsychiatry between a state mental
hospital and the Nebraska Psychiatric Institue using
microwave link

95. Early systems
• 1950’s (USA): NASA and the US Public Health
Services developed a joint telemedicine programme
to serve the Papago Indian Reservation in Arizona.
• 1960’s (USA): Two-way closed-circuit television
systems to facilitate both the transmission of medicalsystems to facilitate both the transmission of medical
images such as radiographs as well as consultations
between doctors.
• 1970’s (USA): Paramedics in remote Alaskan and
Canadian Villages connected with hospitals in distant
towns and cities using the ATS-6 satellite systems

96. Early systems
• 1971, Japan: First time implemented in two areas:
Nakatsu-mura and Kozagawa-cho, Wakayama using
telephone line for voice and Fax transmission and CATV
system for image transmission.
• 1972, Japan: Between Aomori Teishin Hospital and• 1972, Japan: Between Aomori Teishin Hospital and
Tokyo Teishin Hospital over 4 Mhz TV channel and
several telephone lines.
Other systems came up for teleradiology
in several places in Japan like, Nagasaki, Tokai etc.

97. Applications in different forms
• Information exchange between Hospitals and
Physicians.
• Networking of group of hospitals, research centers.
• Linking rural health clinics to a central hospital.
• Videoconferencing between a patient and doctor,• Videoconferencing between a patient and doctor,
among members of healthcare teams.
• Training of healthcare professionals in widely
distributed or remote clinical settings.
• Instant access to medical knowledgebase, technical
papers etc.

98. Benefits of Telemedicine
• Improved Access
Covers previously unserved or underserved areas.
• Improved quality of care
Enhanced decision making through collaborative efforts.
• Reduced isolation of healthcare professionals• Reduced isolation of healthcare professionals
Peer and professional contacts for patient
consultations and continuing education.
• Reduced costs
Decreased necessity for travel and optimum uses
of resources.

99. Telemedicine
• Means "distance healing“.
• Derived from a Greek word "Tele" meaning
"distance" and a Latin word "mederi" meaning
"to heal“."to heal“.
• Is not one specific technology but a way of
providing healthcare services at a distance using
telecommunications technology, medical
expertise & computer science.
• Telemedicine is the future of global healthcare.

101. Types of Telemedicine
Realtime (synchronous)Realtime (synchronous)
Store and Forward
(asynchronous)

102. Realtime (synchronous)
• Could be as simple as a telephone call or as complex as
robotic surgery.
• Requires the presence of both parties at the same
time.
• E.g. : Video-conferencing equipment• E.g. : Video-conferencing equipment
• There are also peripheral devices which can be
attached to computers or the video-conferencing
equipment which can aid in an interactive examination.
• For instance, a tele-otoscope allows a remote physician
to 'see' inside a patient's ear; a tele-stethoscope allows
the consulting remote physician to hear the patient's
heartbeat

103. Store and Forward (asynchronous)
• Involves acquiring medical data (like medical images,
biosignals etc) and then transmitting this data to a doctor
or medical specialist at a convenient time for assessment
offline.
• Does not require the presence of both parties at the same
time.
• Dermatology, radiology, and pathology.• Dermatology, radiology, and pathology.
• A properly structured Medical Record preferably in
electronic form should be a component of this transfer.
• Teleradiology, the sending of x-rays, CT scans, or MRIs
(store-and-forward images).
• Many radiologists are installing appropriate computer
technology in their homes, so they can have images sent
directly to them for diagnosis, instead of making an off-
hours trip to a hospital or clinic.

104. Application Adopted
• Most beneficial for populations living in isolated
communities and remote regions and is currently being
applied in virtually all medical domains.
• Use a "tele-" prefix;
• Useful as a communication tool between a general
practitioner and a specialist available at a remote
• Useful as a communication tool between a general
practitioner and a specialist available at a remote
location.
– Telepathology
– Telecardiology
– Teleradiology
– Telesurgery
– Teleopthalmology

105. Telemedicine
Application
Home Care
and
Ambulatory
Remote
Consultation
and Critical
Care
Monitoring
Disaster
Management
Application
Medical
Education
and Public
Awareness
Second
Opinion
Telementored
Procedure/
Robotic
Surgery

106. Advantages of Telemedicine
• Resource utilization
• Early intervention
• Avoids unnecessary transportation
• Community based care• Community based care
• Medical education and research
• Cost saving
• Improved patient documentation
• Increased range of care and education.

107. Resource Utilization
• In India doctor population ratio is 1:15000 in
comparison to 1:500 in developed nations, and these
doctors are not distributed equally.
• 80% Indian population lives in rural and semi urban• 80% Indian population lives in rural and semi urban
areas.
• Telemedicine can help in cost effective utilization of
meager resources and of the same time can decrease
patient work load on few referral centers.

108. Early Intervention
• There are factors that inhibit the continuity of
care. Issues such as geographic location,
inclement weather, socioeconomic barriers.
• Patient apathy are significant factors that delay
and even prevent the specialty care.
• By providing these primary cure sites with the
ability to quickly access specialty consultation
services.
• Patients are able to reap the benefits of early
intervention while the health care system
maintains quality service and clinical efficiency.

109. Avoids Unnecessary transportation
• Patient can discuss the issues on Video
Conferencing with the consultant.
• Even the vital parameters and be captured with
the help of devices and sent to doctor.the help of devices and sent to doctor.
• Unnecessary referral and patient transport can
be definitely avoided.

110. Community base Care
• People like to receive high quality care in their
local community.
• This reduces travel time and related stresses
associate with many referrals.associate with many referrals.

111. Medical Education and Research
• When medical students are posted in rural area
they can be linked to medical college for grand
rounds and they can also do case presentation
to teachers in medical colleges.to teachers in medical colleges.
• Physicians living in different parts of the world
also use telemedicine in collaborative research,
they can also share data or can discuses current
trends.

112. Cost Saving
• Reduced physician’s fees and cost of medicine.
• Reduced visits to special hospitals.
• Reduced travel expenses.

116. Telemedicine Infrastructure
• This will include minimum standards for all the
hardware and software used in a telemedicine system.
• Under hardware it will include standards and
guidelines for basic telemedicine platform, servers,guidelines for basic telemedicine platform, servers,
clinical devices, video conferencing system,
communication hardware and power support.
• The software standards address operating system,
telemedicine software, and server software.

117. HardwareHardware
• Telemedicine platform
– This will include minimum standards for type of platform to be used,
processor/minimum speed, memory requirements, interfaces, and
peripherals.
• Clinical devices
– This will include minimum standards for all the clinical devices to be
interfaced or integrated with the telemedicine system, including
performance specifications for devices measuring diagnostic parameters,performance specifications for devices measuring diagnostic parameters,
imaging devices, compression, and their safety requirements.
• Video conferencing units
– This will include minimum standards for video conferencing system,
including data rate, picture resolution, frame rate, type of camera, audio
quality etc.
• Communication hardware
– This will include minimum standards for various hardware used for
interfacing the telemedicine system with the communication network,
including all types of terrestrial and satellite based networks.

118. Software
• An operating system
• Licensed telemedicine S/W with appropriate
User Interface(UI)
• Back-end Data Base with the mandatory• Back-end Data Base with the mandatory
tables/ fields (if applicable)

119. Connectivity
• Options for telemedicine services
– VSAT
– PSTN
– ISDN– ISDN
– Leased Line
– Wireless LAN /WAN

120. Telemedicine Tools

121. Barriers of Telecommunication
• Low or small bandwidth.
• Neither telephone lines nor electricity in rural and
remote areas.
• Satellite transmission can help but it is very costly.
• Unstable electricity supply.• Unstable electricity supply.
• Patient’s fear and unfamiliarity.
• Financial unavailability.
• Lack of basic amenities.
• Literacy rate and diversity in languages.
• Quality aspect.
• Government support.

122. Need of Telemedicine in India
• The advances in Medical science, biomedical
engineering on one side and Telecommunication and
Information Technology on the other side are offering
wide opportunities for improved health care.
• Health coverage to majority of our population is still a
distant dream.
• India is a vast country gifted with rich and ancient• India is a vast country gifted with rich and ancient
historic background and geographically the nature has
provided India with all the varieties like the mountain
regions like Ladakh, deserts, green planes and far flung
areas in the north east and offshore islands of
Andaman’s and Lakshadweep.
• 1 billion population.
• Predominantly rural and distributed in distant
geographical locations.

123. Need of Telemedicine in India
• Further this is compounded by the following
factors like:
– High cost of health care and lack of investment for– High cost of health care and lack of investment for
health care in rural areas.
– Inadequate medical facilities in rural &
inaccessible areas.
– Problem of retaining doctors in rural areas where
they are required to serve & propagate
widespread health awareness.

124. Need of Telemedicine in India
• A recent survey by the Indian Medical society has
found
• 75% of qualified consulting doctors practice in urban
centers and
• 23% in semi urban areas and
• only 2% from rural areas whereas majority of the
patients come from rural areas.
• only 2% from rural areas whereas majority of the
patients come from rural areas.
• Hospital beds / 1000 people is 0.19 in rural and
• 2.2 in urban areas.
• This calls for innovative methods of utilization of
science and technology for the benefit, of our society
and telemedicine assumes a great significance to
revolutionize the health care system in India.

125. Available today
• mHealth

128. Wi-Fi Smart
Scale
Otoscope Blood Pressure
Monitor
Bluetooth
Stethoscope
Blood Glucose
Meter
Digital
Thermometer

129. Robotics
Remote Surgery
Live Monitoring
via Cell Phones

130. At Home, at the Office,
on the Go, at a Kiosk