Biomedical Instrumentation Unit 2 - Study Material for TE Instrumentation students, SPPU, Pune

1. By,
Navya Sethu,
Assistant Professor,
Instrumentation & Control Department
PDEA’s College of Engineering, Manjri
Affliated to SPPU, Pune
CARDIO VASCULAR SYSTEM

2. Functions of CVS
- Transport system of body.
- It carries :
1. O2 from lungs to tissues.
2. CO2 from tissues to lungs.
3. Foods from GIT to tissues.
4. Waste products from cells to kidney.
5. Hormones from endocrine glands to other organs.
6. Surplus heat from different parts of body to skin.

3. Blood travels through the heart twice
before returning to the body
The double circulatory system

4. • Pulmonary Circulation
– Carries blood to lungs and back to the heart
• Systemic Circulation
– Carries blood to body and back to the heart
Two Pathways

5. Circulatory System Structures
• Heart
• Blood Vessels
– Arteries
– Veins
– Capillaries
• Blood

6. Arteries:
carries blood away from heart
– Large
– Thick-walled, Muscular
– Elastic
– Oxygenated blood
• Exception Pulmonary Artery
– Carried under great pressure
– Steady pulsating
Arterioles: smaller vessels, enter tissue
• Small branches of arteries.
• Act as control valves through which blood supplies to
capillaries.

7. • Coronary artery
– Supply blood to heart
muscles.
– About 5-7% of blood flows
though the coronary
arteries.

8. Capillaries
– Smallest vessel
– Microscopic
– Walls one cell thick
– Nutrients and gases, hormones, electrolytes etc.
diffuse here

9. Veins:
Carries blood to heart
– Serves as reservoir of blood.
– Carries blood that contains waste and CO2
• Exception pulmonary vein
– Blood not under much pressure
– Valves to prevent much gravity pull
Venules: larger than capillaries
• Collect blood from capillaries .
• Gives deoxygenated blood to veins.

10. Structure of Heart
• Four chambers
– Two upper (Atria)
• Right Atria
• Left Atria
– Two lower (Ventricles)
• Right Ventricle
• Left Ventricle

11. • Two atria are seperated by inter-atrial septum.
• Two ventricles are seperated by inter-ventricular septum.
• Atria is seperated from ventricles by atrio-ventricular septum.
• Heart is enclosed in
pericardium, pericardial
fluid present in
pericardial cavity.
• Myocardium- muscular
wall of heart, Muscles are
arranged in circular and
spiral patterns
• Endocardium- Lines the
internal walls of the heart

12. Valves of Heart
4 sets of valves are present in heart.
A. Two Atrio-ventricular valves:
1. Rt. Atrio-ventricular valve
– Tricuspid valve
2. Lt. Atrio-ventricular valve
– Bicuspid valve (Mitral valve)
B. Two semilunar valves:
1. Aortic valve
2. Pulmonary valve

13. External view of the heart
pulmonary
artery
pulmonary
vein
coronary
artery
left
ventricle
right ventricle
inferior
vena cava
right atrium
pulmonary
vein
aorta
superior
vena cava

14. DIAGRAM

15. The vena cava carries deoxygenated
blood from the body to the right atrium
superior
vena cava
(transports blood
from the head)
inferior
vena cava
(transports blood
from rest of body)

16. The right atrium collects deoxygenated
blood and pumps it to the right ventricle
right atrium

17. The right ventricle pumps deoxygenated
blood to the lungs
right ventricle

18. The pulmonary artery carries deoxygenated blood
from the right ventricle to the lungs
aorta

19. The septum separates the left and right
sides of the heart
septum

20. The pulmonary veins carry oxygenated
blood from the lungs to the left atrium
Pulmonary
veins

21. The left atrium collects the oxygenated
blood and pumps it to the left ventricle
Left atrium

22. The left ventricle pumps oxygenated
blood to the body via the aorta
Left ventricle

23. The aorta carries the oxygenated from the
left ventricle to the rest of the body
Aorta
Aortic arch

24. Atrio-ventricular valves prevent backflow
of blood into the atria when ventricles
contract
Bicuspid valve
(mitral valve)
Tricuspid valves
Tendon

25. The semi-lunar valves prevent backflow of
blood from the arteries into the ventricles
Aortic semi-lunar
valve
Pulmonary
semi-lunar
valve

26. ORIGIN AND CONDUCTION OF
HEART BEAT
1. SA-NODE (SINO-ATRIAL NODE)
• Called pacemaker as it is first to originate the
cardiac impulses & determines the rate of heart
beat.
• Cardiac impulses conducted along the tract of
special cardiac muscle fibres over both the
auricles.
• Lies in the right atrium at the junction of superior
venacava.

27. 2. AV-NODE(ATRIO-VENTRICULAR NODE)
• Stimulated by the waves of contraction
initiated by SA-node.
• Generates cardiac impulses, which are
conducted to the muscles of ventricles
through BUNDLE OF HIS & PURKINJE FIBRES.
• Lies in right posterior of inter-atrial septum.

28. 3. BUNDLE OF HIS
• Arises from AV node, goes towards apex.
• At their terminal end, it give branches called
PURKINJE FIBRES.

32. CARDIAC CYCLE
• Sequence of coordinated events which take place during a
heartbeat.
• Cardiac cycle involves , the phase of contraction called systole &
the phase of relaxation called diastole.
• A complete heart beat consists of a systole & diastole of both atria
and that of both the ventricles.
• The two atria contract at the same time, then they relax while the
two ventricles simultaneously contract.
• The contraction phase of the ventricle chambers is called systole.
• The relaxation phase is called diastole.
• At a normal heart rate, one cardiac cycle last for 0.8 seconds!

33. STEPS INVOLVED IN A CARDIAC CYCLE
1. Atrial systole – contraction of atria
2. Ventricular filling
3. Ventricular systole – first heart sound ‘lubb’
produced with longer duration (0.1 – 0.90
sec.).
4. Ventricular diastole – second heart sound
‘dubb’with shorter duration (0.10 sec.)

37. ElectroCardioGraph – Instrument which records
the electrical activity of the heart.
ElectroCardioGram – The recorded graph from
electrocardiograph
Provides information about a wide range of
cardiac disorders.
Used in catheterization laboratories, coronary
care units and for routine diagnostic
applications in cardiology.

39. • Lead Selector
– The electrodes are selected two by two according to the lead program
• Pre-amplifier
– A three or four stage differential amplifier
– Have a large negative current feedback, from the end stage to the first
stage
• Power amplifier
– Generally push-pull differential type
• Frequency selective network
– Usually, an R-C network
– Provides necessary damping of the pen motor and is preset by the
manufacturer
• Auxillary Circuits
– Provide a 1mV calibration signal and automatic blocking of the
amplifier during a change in position of the lead switch.
– May include a speed control circuit for the chart drive motor

40. ECG Leads
The tracing of voltage difference at ant two
electrode sites due to electrical activity of the
heart is called a “LEAD”
ECG Lead Systems (12-lead system)
1. Bipolar Leads (3)
2. Unipolar Leads (3)
3. Unipolar Chest Leads (6)

42. ECG Electrode Placement

43. BIPOLAR LIMB LEAD SYSTEM
 Electrodes are placed in Right Arm, Left Arm and Left Leg
 Bipolar leads represent the potential difference between
two selected sites.
LEAD I : P.D between LA & RA
LEAD II : P.D between LL & RA
LEAD III : P.D between LL & LA
An electrode placed in Right Leg is earthed though the ECG
machine for
• For the electrical protection of the patient
• To eliminate electrical interference in the recordings

45. In each of these lead positions, QRS of normal
heart is such that
• R- wave is positive
• Lead II produces largest R-wave potential
When amplitudes of three limb leads are
measured, the R-wave amplitude of Lead II is
Lead II = Lead I + Lead III
This equation can be represented by the vector
relationship, as shown in the equilateral triangle.

46. EINTHOVEN TRIANGLE
The Einthoven vector contains all the information of
the three separate lead components and represents
the ‘electrical axis’ of the heart.

47. UNIPOLAR LIMB LEAD SYSTEM
(AUGMENTED LEAD SYSYTEM)
• Measures the electrical activity from one limb at a
time
• leads that take a composite potential from 3 limbs
simultaneously, where signal from 2 limbs are
summed in a resistor network and then applied to
an inverting amplifier input and remaining limb
electrode is applied to the non-inverting input

48. • Lead aVR - RA connected to non-inverting input
while LA and LL are summed at inverting input
augmented (amplified) Voltage for Right arm(aVR)
• Lead aVL - LA connected to non-inverting input while
RA and LL are summed at inverting input augmented
(amplified) Voltage for Left arm(aVL)
• Lead aVF - LL connected to non-inverting input while
RA and LA are summed at inverting input augmented
(amplified) Voltage for Foot(aVF)

50. BIPOLAR LEADS
• Lead I is the voltage difference between the LA and RA
electrodes (LA – RA), directed towards LA at 0°
• Lead II is the voltage difference between the LL and RA
electrodes (LL – RA), directed towards LL at +60°
• Lead III is the voltage difference between the LL and LA
electrodes (LL – LA), directed towards LL at +120°
AUGMENTED UNIPOLAR LEADS
• Lead aVR is directed towards the RA electrode (-150°),
calculated as follows: aVR = RA – (LA + LL)/2.
• Lead aVL is directed towards the LA electrode (-30°)
calculated as follows: aVL = LA – (RA+LL)/2
• Lead aVF is directed towards the LL electrode (+90°),
calculated as follows: aVF = LL – (LA + RA)/2

52. UNIPOLAR CHEST LEADS
Constituted by an indifferent electrode
resulting from a connection between all three
standard limb leads and an exploring electrode
placed on 6 points on the chest wall.
The indifferent electrode forms the negative
terminal and the exploring electrode forms the
positive terminal

53. Placement of precordial
leads– V1 - 4th intercostal space,
right of sternum
– V2, 4th ICS , left of sternum
– V3 - Midway between V2 &
V4
– V4 - 5th ICS , midclavicular
line
– V5 - 5th ICS anterior axillary
line
– V6 - 5th ICS mid axillary line

55. 12 LEAD ECG SYSTEM

56. ECG amplifier

59. Feature Description Duration
RR interval
The interval between an R wave and the next R wave; normal resting heart rate
is between 60 and 100bpm.
0.6 to 1.2 s
P wave
During normal atrial depolarization, the main electrical vector is directed from
the SA node towards the AV node and spreads from the right atrium to the
left atrium. This turns into the P wave on the ECG.
80ms
PR interval
The PR interval is measured from the beginning of the P wave to the beginning
of the QRS complex. The PR interval reflects the time the electrical impulse
takes to travel from the sinus node through the AV node and entering the
ventricles. The PR interval is, therefore, a good estimate of AV node function.
120 to 200 ms
PR segment
The PR segment connects the P wave and the QRS complex. The impulse
vector is from the AV node to the Bundle of His to the bundle branches and
then to the Purkinje fibers. This electrical activity does not produce a
contraction directly and is merely traveling down towards the ventricles, and
this shows up flat on the ECG. The PR interval is more clinically relevant.
50 to 120 ms
QRS complex
The QRS complex reflects the rapid depolarization of the right and left
ventricles. The ventricles have a large muscle mass compared to the atria, so
the QRS complex usually has a much larger amplitude than the P-wave.
80 to 100 ms
ST segment
The ST segment connects the QRS complex and the T wave. The ST segment
represents the period when the ventricles are depolarized. It is isoelectric.
80 to 120 ms

60. T wave
The T wave represents the repolarization (or recovery) of the ventricles. The
interval from the beginning of the QRS complex to the apex of the T wave is
referred to as the absolute refractory period. The last half of the T wave is
referred to as the relative refractory period (or vulnerable period).
160 ms
ST interval The ST interval is measured from the J point to the end of the T wave. 320 ms
QT interval
The QT interval is measured from the beginning of the QRS complex to the end
of the T wave. A prolonged QT interval is a risk factor for ventricular
tachyarrhythmias and sudden death. It varies with heart rate and, for clinical
relevance, requires a correction for this, giving the QTc.
Up to 420 ms in
heart rate of
60 bpm
U wave
The U wave is hypothesized to be caused by the repolarization of the
interventricular septum. It normally has a low amplitude, and even more often is
completely absent. It always follows the T wave, and also follows the same
direction in amplitude. If it is too prominent, suspect hypokalemia,
hypercalcemia or hyperthyroidism.