This document discusses various measurement and analysis techniques used in medical diagnostics, including blood flow meters, cardiac output measurement, blood gas analyzers, and electrophoresis. It provides detailed descriptions of the principles and procedures for three types of blood flow meters (ultrasonic and electromagnetic), three methods for measuring cardiac output (Fick's method, indicator dilution, and thermodilution), blood gas analyzer components and measurements, principles of electrophoresis using cellulose acetate, and analysis of electrophoresis results.

1. UNIT II
MEASUREMENT AND
ANALYSIS TECHNIQUES
• BLooD fLow METERS
• CARDIAC oUTpUT MEASUREMENT
• BLooD gAS ANALYzERS
• ELECTRopHoRESIS
• pULMoNARY fUNCTIoN ANALYzERS
Prepared by,
A.Johny Renoald M.E., (Ph.D.,)

2. Blood flow meters
Three types:
(i)Transit Time Ultrasonic Blood Flow Meter (ii) Doppler Shift Ultrasonic Blood
Flow Meter. (iii) Electromagnetic Blood flow meter
BFM is the equipment used to measure the flow of the blood in the vessels
for the purpose of easy way to diagnosis.
(i) Transit Time Ultrasonic Blood Flow Meter:
Two ultrasonic transducers (piezoelectric crystals)
are placed on either side of the blood vessel at an
oblique angle to the flow axis and at a distance D
from each other.

3. Up- & downstream transit times are measured with B as transmitter and A as
receiver and vice versa, respectively. They are given by

4. The difference in up- & downstream transit times is
(ii) Doppler Shift Ultrasonic Blood Flow Meter:
Two ultrasonic transducers (piezoelectric crystals) are placed on the same side
of the blood vessel with one transducer acting as transmitter and the other as
receiver.

5. Principle:
The principal is, as the name itself implies, the Doppler effect i.e.,
The following figure shows the schematic diagram of the process.

6. iii.Electromagnetic Blood flow meter:
Principle: ( Faradays law of Induction)
A voltage is created when a moving conductor “cuts” the flux of a magnetic field. If that
conductor is a blood carrying vessel of diameter ‘a’, then the voltage generated is given by
E=(QB)/(50πa) μV

7. Block diagram of Blood flow meter

8. •The oscillator which drives the magnet and provides a control signal for the gate
operates at a frequency between 60 and 400Hz.
•The use of gated detector makes the polarity of the output signal reverse when the
flow direction reverses.
• The frequency response of this type of system is usually high enough to allow the
recording of the flow pulses while mean or average flow can be derived by use of
a LOW PASS FILTER.
• Blood flow is made to pass in magnetic field and the magnetic current is provided
by an oscillator.
• Whenever blood is flowing, amplifier senses the difference, amplifies and is given
to gate.
• The output of the gate is in the form of pulses with respect to blood flow.
• Finally the signal is filtered to give average value of blood flow through that blood
vessel.

9. •Cardiac output is the amount of blood delivered by the heart to the aorta per minute
•For adult the cardiac o/p is about 4-6 litters / minute.
•CARDIAC O/P = Stroke Volume X Heartbeat rate/Min
There are three types
1.FICK`S Method
2.INDICATOR DILUTION Method
3.THERMO DILUTION Method
• Using this method the cardiac o/p is determined by the analysis of the gas
keeping of the organism.
• It is calculated by continuously infusing oxygen into the blood or removing it from
the blood and measuring the amount of the oxygen in the blood before and after
its passage.

10. O2
VENA CAVA
Oxygen uptake by ventilation
HEART
&
LUNGS
QHeart Catheter
Arterial Blood
Aorta

11. Let I be the amount of infused or removed oxygen per unit time and is equal to
the difference between the amounts of blood arriving at and Departing from the
site of measurement.
I = CA Q - CV Q
Q = I/ CA – CV
Q = Cardiac o/p Lit/Min
CA = Concentration of Oxygen of outgoing Blood (Arterial Blood)
CV = Concentration of Oxygen of incoming Blood ( Mixed Venus Blood)
I = Volume of Oxygen uptake by Ventilation
CA – Samples taken from an artery in the fore arm.
CV – Samples taken from Central vein through a cardiac catheter
I – Determined by analyzing the exhaled air collected in a bag during 10 min

12. We introduce a known amount of dye or radio isotope as an indicator in the blood
circulation and then measuring the concentration of the indicator w.r.t. time at the
measurement site, we can estimate the volume of the blood.
 Let M mg of an indicator injected in to the large vein (right Heart itself).
 After passing through the right heart, lungs and left heart the indicator appears
in the arterial circulation.
 The presence of indicator in the artery is detected by detector. The O/p of the
detector is directly proportional to the concentration of the indicator.
 The detector is displayed on a chart recorder w.r.t. time.
 dv – Incremental Volume dt – Sampling site time dM – Mass of indicator
Then dV=dM
 Therefore Concentration of the indicator C = dM/dv
Now dM /dt = C dv/dt
but we know dv/dt = Cardiac output Q. Therefore dM = Q Cdt.

13. Integration over the time
t
M = ∫ Q Cdt
0
Consider the flow as constant
t
M =Q ∫ Cdt
0
M
Or Q = ------------------
t
∫ Cdt
0
C is the function of time. By drawing a curve b/w Concentration and time the area
under the curve Gives directly the value of ∫ Cdt.
i.e Q = M / area of the curve
Disadvantage:
The foreign substances is injected into the blood is also taken out for analysis

14. Principle:
Thermal indicator of known volume introduced in to either right or left atrium will
produce a resultant temperature change in the pulmonary artery or in the Aorta
respectively. The integral of which is inversely proportional to the Cardiac output.
“a constant” X (Blood temp – Injectate Temp)
Cardiac O/P = -----------------------------------------------------------
Area under the dilution curve
PROCEDURE:
• 10 milliliters of 5% dextrose in water at room temperature is injected as a thermal
indicator in to the right atrium.
• After mixing it is detected in the pulmonary artery by a thermistor, placed at the
tip of a miniature catheter probe.

15. Thermistor for
Blood temp
Thermistor for
Temp of thermal
indicator
Amplifier
Amplifier
Integrator
circuit
Micro
controller
Preset
adjustment
control
Output
Display Unit
Timer / Control
Unit
To the output of
microcontroller
dM/dt = C dv/dt
Block Diagram

16. • The temperature difference between the injectate temperature and the
circulating blood temperature in the pulmonary artery is measured.
• The reduction in temperature is integrated with respect to time. It is
displayed in the output unit.After applying corrections ,the cardiac
output is displayed in litres per minute.
• Amplifier block is used to remove the non linearity of the thermistor.

17. ELECTROPHORESIS
BASIC PRINCIPLE:
• Electrophoresis is defined as the movement of solid phase with respect
to a liquid (buffer solution).
• The buffer solution is used to carry current Sand to maintain the pH
value of the solution as a constant one during migration.
FACTORS THAT AFFECT THE SPEED OF
MIGRATION.
• Magnitude of charge.
• Ionic strength of buffer.
• Temperature
• Time
• Type of support media.

18. CELLULOSE ACETATE ELECTROPHORESIS
• Cellulose acetate is the most commonly used solid medium.
• Other possible mediums are paper, starch gel, agar gel, sucrose,
etc.
• Buffer solution is taken in two beakers. Electrodes are placed in the
buffer solutions as anode and cathode.
• A strip of cellulose acetate is placed as a bridge between the buffer
solutions.
• A voltage of 250V with an initial current of 4-6mA is applied across
the medium through the buffer solution for 15-20 min. Then the
electric voltage is removed.

19. CELLULOSE ACETATE ELECTROPHORESIS

20. • A fixative and a dye are used to fix and stain the migrated particles on
the medium.
• Finally a densitometer is used to measure the densities of the
migrated particles on the medium. A plot of density versus migration
distance is made from this measurement.

21. BLOOD GAS ANALYZERS
BGA are used to measure the pH, Partial pressure of carbon dioxide
(pCO2 ) and Partial pressure of Oxygen (pO2 ) of the body fluids with
special reference to the human blood.
(i) pO2:
• Normal range: 80-100 mm Hg.
• Hypoxemia: Lack of O2 i.e., reduction in pO2 due to bronchial
obstruction, blood vessel and hemoglobin abnormalities.
(ii) pCO2:
• Normal range: 35-45 mm Hg.
• Hypercapnia: Increase in pCO2 due to cardiac arrest, chronic
obstructive lung disease, chronic metabolic acid-base disturbances.
(iii) pH:
• Normal range: 7.35-7.45
• Alkalosis: Increase in pH due to increase in bicarbonates (HCO3)
• Acidosis: Decrease in pH due to decrease in bicarbonates (HCO3)

22. BASic pRiNcipLE:
• The blood gas analyzer consists of three types of electrode
systems for the measurement of pH, pO2 and pCO2
respectively and a sample chamber.
• The electrode systems and the sample chamber are located
inside a temperature-controlled block maintained at 37oC
(human body temperature).
• The blood sample is first injected into the sample chamber
where it undergoes a temperature equilibration before
measurement.

23. pH MEASUREMENT

24. pH MEASUREMENT
• Two electrodes are used:
(i) a calomel or Ag/AgCl reference electrode immersed in a Kcl
solution and closed by a leaky membrane that permits a current
flow from the reference electrode via the sample in the sample
chamber to the measuring electrode.
(ii) a Ag/AgCl measuring electrode immersed in a solution of constant
pH and closed by a glass membrane that is sensitive to H+.
 As the sample passes through the chamber, the difference in H+
ion concentration on either side of the glass membrane changes
the potential at the measuring electrode.

25.  The reference electrode produces a constant potential
irrespective of H+ concentration in the sample.
 The change in the potential at the measuring electrode is
detected by a voltmeter, which has been calibrated in pH units.
So the pH is defined as logarithmic of the reciprocal value of H+
ion concentration. The pH equation is given as
pH = - log10[H+
] = log10 x 1/[H+
]
pH is the acid base balance in a fluid.

26. pO2 MEASUREMENT
• A polar graphic electrode system consisting of (i) a Ag/Agcl
reference electrode (anode) and (ii) a thin platinum wire (cathode)
both immersed in an electrolyte (H2O) and separated from the
sample by a O2 permeable membrane.
• A potential of 0.7V is applied between these electrodes. The
current generated by the system is the measure of pO2 in that
sample.
• The partial pressure of a gas is proportional to the quantity of that
gas present in that blood. There are two types
• Vitro – Blood sample is taken for measurement
• Vivo – Meaurement is done while the blood is flowing

27. pO2 MEASUREMENT

28. pCO2 MEASUREMENT
• A Severinghans pCO2 electrode consisting of
• (i) a Ag/Agcl reference electrode and
(ii) a glass pH electrode both immersed in an electrolyte and
separated from the sample by a CO2 permeable membrane and
a spacer which acts as a support for the aqueous HCO3 layer.
• Diffusion of CO2 alters the pH of the electrolyte thereby changing
potential output of this modified pH electrode. This gives the
pCO2 in the sample.
H2O + CO2 ® H+
+ HCO3

29. pCO2 MEASUREMENT

30. pULMONARY FUNCTION ANALYZERS
There are three types of measurements. 1.Ventilation 2.Distribution 3.Diffusion
Ventilation: This is performed using devices called Spiro meters that measure
Volume displacement and the amount of gas moved in a specific time.
Distribution: Measurements quantify degrees of lung obstructions and also
determine the residual volume, which is the amount of air that can not be
removed from the lungs by the patient effort.
Diffusion: Measurements identify the rates at which gas is exchanged with the
blood stream.
So the pulmonary function analyzers provide the means for automated
clinical procedures and analysis techniques for carrying out a complete
evaluation of the lung function or the respiratory process.

31. SpIRO METER
•The instrument used to measure lung capacity and volume is called Spiro
meter.
•Basically the record obtained from this device is called spirogram.
•Spirometers are calibrated containers that collect gas and make
measurements of lung volume or capacity that can be expired.
•By adding a time base, flow dependent quantities can be measured.

32.  The spirometer consists of a water tank, a bell-jar immersed upside down
into the water and a tube extending into the air space inside the bell-jar.
 One end of a string is attached to the bell-jar and the other to a weight via
two bulleys. The subject is asked to breathe into the tube via the mouth piece.
 During every cycle of inspiration and expiration, the bell-jar moves up and
down depending on the volume of air inspired or expired into or from the air
space inside the jar.
 The weight attached to the other end of the string moves up and down
accordingly. A pen may be attached to the weight to make a graph on a paper
attached to a rotating drum.
 Otherwise the third arm of a potentiometer may be attached to the weight to
obtain an electrical signal corresponding to the movement of the weight.
 The resultant graph is called the Kymograph.

33. 1.LUNG VOLUMES AND CpACITIES
2.COMpLETE GAS ANALYZER
3.COMpLETE pULMONARY ANALYZER

34. V.SARAVANAN B.E,M.TECh
ASSISTANT pROFESSOR / ECE
VIVEkANANDhA COLLEGE OF ENGINEERING FOR WOMEN
ELAYAMpALAYAM
TIRUChENGODE.