Lab 11: Circulatory System: Blood pressure, blood typing, and ECG
A. Blood pressure: With your lab partner, use a sphygmomanometer and stethoscope to
measure each other’s blood pressure:
1) Expose the upper arm and wrap the cuff of the sphygmomanometer above the bend
of the elbow; secure with the Velcro.
2) Close the valve on the bulb pump, and inflate the cuff to approximately160 mm Hg.
3) Place the stethoscope on the brachial artery. Slowly release the pressure in the cuff,
and listen while you watch the needle fall on the pressure gauge.
4) When you first hear the pulsations of blood squirting through the brachial artery,
note the pressure on the gauge. This is the systolic pressure.
5) When the sound disappears, this is the diastolic pressure.
6) Report both as a ratio (e.g. 120 / 80).
Your blood pressure:________________.
B. Heart (pulse) rate: Listen to your heart with the stethoscope, and count the number of
beats.
1) Place the stethoscope over your heart and count the number of beats for 15 seconds.
2) Likewise, measure your pulse rate at the carotid (neck) & radial (wrist) arteries for 15
seconds.
3) Convert all measurements (x4) to generate bpm (beats per minute).
Results
Stethoscope on heart:
_______ bpm.
At carotid artery:
_______ bpm.
At radial artery:
_______ bpm.
C. Blood typing: If you dare, use an autolancet to draw a bit of your blood and mix with
antibodies to determine your blood type (ABO, + or –).
1) Wash your hands with soap and water. Dry with clean paper towels.
2) After obtaining a test card, an autolancet with needle & guide, three toothpicks, and
two alcohol swabs, the instructor will place a drop of each antibody on the test card in
the labeled spots. (DO NOT TOUCH THE ANTIBODIES YOURSELF)
3) Swab the tip of your non-dominant ring finger with the alcohol swab, and
immediately prick with the autolancet.
4) Keep the pricked finger below your heart and squeeze it at the base of the finger
with your free hand to stimulate blood flow. (DO NOT TOUCH THE BLOOD)
5) Carefully place a drop of blood alongside each antibody in the designated spots on
the test card.
6) Using the appropriate color-coded toothpick, gently push the antibody and blood
together, and mix carefully to avoid contaminating the other drops. (DO NOT SCRAPE
THE TOOTHPICK ALONG THE SURFACE OF THE CARD. BLOOD WILL FLY OFF!)
7) Rock the card back and forth to mix further while observing for fine granules (occurs
when antibodies detect their antigens and cause them to clump).
RESULTS
Presence of granules (i.e.,clumps) (+/-):
A antibody:_____
B antibody:_____
Blood type:______________
Rh antibody:_____
D. The Electrocardiogram Recording ECG
The normal rhythm of the heart is established by a specialized bundle of neuromuscular tissue
called the Pacemaker, located in the SA (sinoatrial) Node. The SA Node is a small patch of
specialized tissue found in the wall of the right atrium, near the entrance of the superior vena
cava. The depolarization initiated by the SA Node spreads across the atrial muscle causing the
atrial contraction (atrial systole) which forces blood into the ventricles. The ventricular
contraction phase of the cardiac cycle is brought about by depolarization of the ventricles. The
Purkinje System is a conduction system of specialized fibers which carries the wave of
depolarization (or impulse) from the AV (atrioventricular) Node through the Left and Right
Bundle Branches and then to the Purkinje fibers which diffuses the impulse through the muscle
fibers of the ventricles. The sequence of events which results in a cardiac cycle are:
Electrical Stimulation of the Heart--Sequence of Events:
SA Node Fires → Impulse spreads through the atrial muscle → Atrial Systole → Blood forced into ventricles
Impulse reaches the AV Node → the impulse is “Delayed” then conducted by the L. & R. Bundle Branches to the
Purkinje Fibers → impulse spreads through the ventricular muscle → Ventricular Systole→ Ventricles “eject”
blood into the major vessels leaving the heart (Aorta & Pulmonary Trunk)
In this exercise we will be concerned with the electrical activity associated with the contraction
of the heart and with recording the Electrocardiogram (EKG). The electrocardiograph is the
instrument that monitors electrical activity of the heart. It amplifies the impulses so that they
are strong enough to activate a recording device. Electrodes attached to the surface of the
body receive impulses from the heart. The electrodes are usually of metal and made to make
close contact with the skin. The amplified impulse can be captured by a computer monitoring
system and display the electrical impulses as waves on the computer screen. The record
produced by the electrocardiograph is called an electrocardiogram (abbreviated ECG or EKG).
An EKG is often obtained with a polygraph, a recording instrument that operates on the
principle just described, but is capable of monitoring impulses from several different
physiological activities in addition to that of the heart.
The record is superimposed upon a standardized graph. The x-axis records time in seconds and
the y-axis the amplitude in millivolts (mV). The space between two vertical lines represents
0.04 seconds; the space between two horizontal lines represents 0.1 mV.
The procedure used in taking an EKG involves the application of a electrolyte jelly which forms a
low-resistance surface between the skin and electrode. This material aids the conduction of
electrical signals. Paper pads presaturated with an electrolyte solution can also be used in
place of the jelly. The electrodes are securely held in place by means of straps. The particular
arrangement of two electrodes is called a lead. The position of the electrodes on the body, the
manner in which they are wired to the recording system, and any and all extra movements of
the individual undergoing testing will influence the final record.
The component waves of a normal EKG are shown in Figure 5. The major components include
the following:
P wave:
impulse spreading through the atria (preceding atrial systole)
QRS wave:
depolarization of the ventricular muscle (preceding ventricular systole)
T wave:
repolarization of the ventricular muscle (preceding ventricular diastole)
Procedure: In this part you will be responsible for obtaining a EKG recording and to analyze
each tracing by: (1) Labeling P QRS T waves, (2) Measuring the amplitude of each wave, (3)
Measuring the time of each wave component, and (4) Determining the heart rate by using the
ECG recording.
1. Subject is prepared as directed by lab instructor--the subject should not touch the
electrocardiograph during the recording process. The black wire should be attached
to an electrode on the right ankle; the red wire should be attached to the left wrist;
and the green wire should be attached to the right wrist.
2. The EKG technician(s) should operate the instrument as directed by the lab instructor.
3. Obtain a sufficient length of recording so that heart rate can be determined.
4. Complete Part D WS by using the reference information below to analyze each of the 3
leads. Print your EKG and include it in Part D of the worksheet.
Reference Information: Typical EKG Ranges
Amplitude: (10 small squares = 1 mV; 1 small square = 0.1 mV)
Time: (1 small square = 0.04 sec; 1 large square = 0.20 sec; 5 large square = 1 sec.)
ECG Phase
P wave
P-R interval
P-R segment
QRS complex (R wave)
S-T segment
Q-T segment
T wave
Amplitude (mV)
0.2
0.8-1.2
0.3
Duration (sec)
0.04-0.08
0.12-0.20
0.08
0.04-0.10
0.12
0.40
0.16
Heart Rate based on EKG: _______________