Download Electrocardiography, Blood Pressure

LABORATORY
Week 5
Electrocardiography, Blood Pressure
Objectives
1.
Record an electrocardiogram and analyze the ECG tracings as follows:
a. Correlate the waves, intervals and segments with the electrical activities taking
place in the heart
b. Identify the P wave, P-R interval, P-R segment, QRS complex, S-T segment, and
the T wave.
c. Determine the heart rate, the duration of the P wave, P-R interval, QRS complex,
S-T segment, and the T wave.
d. Compare ECG tracings recorded for a subject at rest, after running in place
(moderate exercise); explain, in physiological terms, the differences observed.
e. Record the ECG and the heart sounds, and with the aid of a stethoscope, listen
to the characteristic sounds of the heartbeat.
2.
Define the following terms: systole, diastole, sounds of Korotkoff, pulse pressure,
mean arterial pressure, stroke volume, and heart rate.
Accurately measure a subject’s systolic arterial pressure and diastolic arterial
pressure using a sphygmomanometer and determine a subject’s pulse rate. Using
these values, determine pulse pressure and mean arterial pressure.
The heart is a pump that pushes blood around the body. Blood enters the heart at a low
pressure and leaves at a higher pressure, and this high pressure provides the force to propel
the blood through the circulatory system. Blood returning from the body is sent to the right side
of the heart and then to the lungs to pick up oxygen and release carbon dioxide. This
oxygenated blood is sent to the left side of the heart and back to the body, where oxygen is
released and carbon dioxide is collected. The complete division of the heart insures that there is
no mixing of deoxygenated blood (in the right side) with oxygenated blood (in the left side).
The mammalian heart is autorhythmic, since it will continue to beat if removed from the body
(and kept in an appropriate solution). Heart contractions are, therefore, not dependent upon the
brain, rather the rhythm comes from within the heart itself. The heart is composed almost
entirely of large, strong muscle fibers (myocardium), which are responsible for the pumping
action of the heart. Other cardiac muscle cells are weakly contractile and produce or conduct
the rhythm for the rest of the heart. A group of these weak muscle cells is located in the
sinoatrial (SA) node and acts as the pacemaker for the heart. These cells rhythmically produce
action potentials, which spread via gap junctions to fibers of both atria. The resulting contraction
5.1
pushes blood into the ventricles. While adjacent atrial fibers are connected by gap junctions, the
only electrical connection between the atria and the ventricles is via the atrioventricular (AV)
node. The action potential spreads slowly through the AV node and then rapidly through the
Bundle of His and Purkinje fibers to excite both ventricles.
The cardiac cycle involves the sequential contractions of the atria and the ventricles which are
triggered by action potentials in the myocardial cells. The combined electrical activity of the
myocardial cells produces electrical currents that spread through the body fluids. These currents
are large and detectable by recording through electrodes placed on the skin. The regular
pattern of signals produced by the heart is called the electrocardiogram or ECG
In this laboratory you will record the electrocardiogram and the finger pulse from a (healthy)
subject. These parameters will be recorded when the subject is at rest and immediately after
exercise.
.
Warning: This experiment involves exercise and an elevation of heart rate. It should not be
performed by anyone who is not healthy or has a personal or family history of
cardiovascular or respiratory problems.
Equipment Required
PC Computer
IWX/214 data acquisition unit
USB cable
IWX/214 power supply
C-AAMI-504 ECG cable and electrode lead wires
PT-104 Pulse plethysmograph
Alcohol swabs
Disposable ECG electrodes
Start the Software
1 Click on the LabScribe shortcut on the computer’s desktop to open the program.
2. On the Main window, pull down the Settings menu and select Load Group.
5.2
3. Locate the folder that contains the settings group, complete IPLMv4.iwxgrp. Select the group
and click Open.
4. Pull down the Settings menu again. Select Human Heart and select the Exercise-ECGCirculation-LS2 settings file in the submenu
ECG Cable and Pulse Transducer Setup
1. Plug the DIN8 connector to the PT-104 into the Channel 3 input
2. Insert the black AAMI connector on the end of the ECG cable into the isolated inputs of
Channels 1 and 2 input
3. Insert the connectors on the red, black, and green electrode lead wires into the matching
sockets on the lead pedestal of the ECG cable..
4. Instruct the subject to remove all jewelry from their wrists and ankles.
5. Use an alcohol swab to clean and scrub a region with little or no hair, on the inside of the
subject’s right wrist. Let the area dry.
6. Remove a disposable ECG electrode from its plastic shield, and apply the electrode to the
scrubbed area on the wrist.
7. Repeat Steps 5 and 6 for the inside of the left wrist and the inside of the right ankle.
8. Snap the lead wires onto the electrodes, so that:
• the red (+1) lead is attached to the right wrist,
• the black (-1) lead is connected to the left wrist,
• the green (C or ground) lead is connected to the right leg.
9. Place the plethysmograph on the volar surface (where the fingerprints are located) of the
distal segment of the subject’s middle finger, and wrap the Velcro strap around the end of the
finger to attach the unit firmly in place.
5.3
10. Instruct the subject to sit quietly with their hands in their lap. If the subject moves, the ECG
trace will move off the top or bottom of the screen. If the subject moves any muscles in the
arms or upper body, electromyograms(EMGs) from the muscles will appear on the ECG
recording as noise.
Activity 1 a: The ECG and the Pulse in a Resting Subject
Aim: To measure and correlate the ECG and the pulse in a resting individual.
Procedure
1. Click on the Record button, located on the upper right side of the LabScribe Main window on
page. The signal should begin scrolling across the screen.
.
2. Click on the AutoScale button at the upper margin of the ECG, Pulse, and Heart Rate
channels. Your recording should look like the figure below
• If the signal on either the ECG or the Pulse channel is upside down when compared to
trace in the above figure , click on the downward arrow to the left of the channel title and
select the Invert function. The trace should now look similar to the one in the figure
• If a larger ECG signal is required, the electrodes should be moved from the wrists to the
skin below each clavicle.
• If the pulse signal is small or noisy, adjust the tension on the strap holding the pulse
plethysmograph to the finger.
3.
5.4
When you have a suitable trace, type <Subject’s Name> Resting ECG/Pulse in the Mark
box to the right of the Mark button. Press the Enter key on the keyboard to attach the
comment to the data. Record for a minute or two.
4.
Click Stop to halt recording.
5.
Select Save As in the File menu, type a name for the file. Choose a destination on the
computer in which to save the file, like your lab group folder). Designate the file type as
*.iwxdata. Click on the Save button to save the data file.
Activity1 b: The ECG and Pulse After Exercise
Aim: To measure and correlate the ECG and the pulse immediately after exercise.
Procedure
1 While the subject is resting, disconnect the C-AAMI-504 cable and the pulse plethysmograph
cable from the IWX/214 unit.
2 Coil up the C-AAMI-504 and the PT-104 cables so the subject can hold the cables in his or
her hand while exercising with the leg muscles, like walking stairs or gently jogging in place or
bench stepping . Remember that the lead wires are still attached to the electrodes, so the
free portion of the cables need to be long enough to allow the subject to move easily, yet
short enough that the subject does not trip.
3 Instruct the subject to exercise for five minutes. Immediately after the exercise period is over,
have the subject sit down and relax next to the recording equipment.
4 Quickly reconnect the C-AAMI-504 and the PT-104 cables to the IWX/214 unit.
5 Click on the Record button. Click AutoScale on all three channels. While recording, type
ECG/Pulse-Recovery from Exercise in the Mark box to the right of the Mark button. Press
the Enter key on the keyboard to attach the comment to the data.
6 Continue recording until the subject’s heart and breathing rates have returned to normal. This
may take less than 2 minutes, or longer than 10 minutes, depending on the fitness of the
subject. Enter marks and comments on the recording at 30 second intervals by typing
comments on the Mark line and clicking on the Mark button or pressing
the Enter key on the keyboard.
7 Click Stop to halt recording.
8 Select Save in the File menu on the LabScribe window.
Data Analysis
Use the following techniques to analyze the data from Exercises 1 and 2. The information
extracted from these exercises will demonstrate the effects of exercise and recovery on heart or
pulse rate.
1 Scroll through the recording and find a section of data with four or five exemplary ECG/Pulse
cycles recorded in succession while the subject was resting.
5.5
2 Place the cursors on either side of a group of four complete ECG/Pulse cycles.
• You can also click the Zoom between Cursors button on the LabScribe toolbar to expand
the segment with the four selected ECG/Pulse cycles to the width of the Main window.
3 Click on the Analysis window icon in the toolbar
4. Look at the Function Table that is above the uppermost channel displayed in the Analysis
window. The names of the mathematical functions used in the analysis, V2-V1 and T2-T1,
appear in this table.
5 Once the cursors are placed in the correct positions for determining the time intervals on
each ECG/Pulse cycle, the values of these time intervals can be recorded( either in the
online journal or on a separate table)
6
Use the mouse to click on and drag the cursors to specific points on the ECG/Pulse
recording to measure the following:
• The beat period, which is the time interval between two adjacent R waves . To measure
the beat period, place one cursor on the peak of a R wave and the second cursor on the
peak of the adjacent R wave. The value for T2-T1 on the ECG channel is the beat period.
Measure the beat period for two additional pairs of R waves.
• The P-R interval. To measure this time interval, place one cursor at the beginning of the P
wave and the second cursor at the beginning of the QRS complex. The value for T2-T1 on
the ECG channel is the P-R interval. Measure this time interval for two additional ECG
cycles.
• The Q-T interval. To measure this time interval, place one cursor at the beginning of the
QRS complex and the second cursor at end of the T wave. The value for T2-T1 on the ECG
channel is the Q-T interval. Measure this time interval for two additional ECG cycles.
5.6
. Calculate the duration of P wave, QRS complex, T wave and the ST segment by placing the
cursors at the appropriate places
• The heart rate, which is expressed in beats per minute and calculated from the average beat
period by using the following equation:
Heart Rate (beats/minute) = 60 seconds/minute
# seconds/beat
Note: Heart Rate can also be determined by looking at the Mean function on the Heart Rate
Channel. The more data on screen - the more accurate the Mean heart rate.
.
7 Scroll through the recording and find a section of data with four or five exemplary ECG/Pulse
cycles recorded in succession when the subject just stopped exercising(Recovery time = 0
seconds). Repeat Steps 2 through 6 for this section of data.
8. Move to the sections of data marked at 30 second intervals throughout the recovery period
began and repeat the measurements performed in Steps 2 through 6.
Activity 1 c:
ECG and Heart Sounds
When the ventricles contract, the pressure of the blood inside the ventricles increases to close
the atrio ventricular valves. Further contraction increases the ventricular pressure until it
exceeds the arterial pressure. At this point, when the arterial pressure is at its lowest point
during the cardiac cycle (called diastolic pressure) the semilunar valves are forced open, and
blood flows into the artery. Blood entering the arterial system inflates the arteries a little and
increases blood pressure to a maximum, which is the systolic pressure.
In this lab activity you will record the ECG and heart sounds from a subject and, with the aid of a
stethoscope, hear those characteristic sounds of the heartbeat, typically described as a "lubdub." These sounds are produced by the closure of the heart valves. The first heart sound or
"lub" results from closure of the tricuspid and mitral valves. It is a rather low-pitched and a
relatively long sound which represents the beginning of ventricular systole. The second heart
sound, or "dub," marks the beginning of ventricular diastole. It is produced by closure of the
aortic and pulmonary (pulmonic) semilunar valves when the intra ventricular pressure begins to
fall. This "dub" sound is typically heard as a sharp snap because the semilunar valves tend to
close much more rapidly than the AV valves. Because diastole occupies more time than systole,
a brief pause occurs after the second heart sound when the heart is beating at a normal rate.
Therefore, the pattern that one hears is one of: "lub-dub" pause, "lub-dub" pause, and so on.
Heart auscultation and ECG are two important tools for cardiovascular disease diagnosis.
Physicians perform diagnoses from listening to heart sounds and by a visual examination of the
ECG waveforms. It has been shown that patients with the same disease tend to have similar
looking ECG shapes with comparable heart sounds.
Equipment Required
PC Computer
IWX/214 data acquisition unit
USB cable
IWX/214 power supply
C-AAMI-504 ECG cable and electrode lead wires
ES-100 electronic stethoscope
Alcohol swabs; Disposable ECG electrodes
5.7
Click on the LabScribe shortcut on the computer’s desktop to open the program.
1 On the Main window, pull down the Settings menu and select Load Group.
2 Locate the folder that contains the settings group,IPLMv4.iwxgrp. Select this group and click
Open.
3 Pull down the Settings menu again. Select Human Heart and select the ECGStethoscopeLS2 settings file in the submenu.
4, Insert the black AAMI connector on the end of the ECG cable into the isolated inputs of
Channels 1 and 2 of the IWX/214 and the electronic stethoscope on Channel 3 input.
5 Repeat steps 3 through 8 in the ECG and pulse transducer set up in page 5.3
.
6. Instruct the subject to sit quietly with their hands in their lap. If the subject moves, the ECG
trace will move off the top or bottom of the screen. If the subject moves any muscles in the
arms or upper body, electromyograms (EMGs) from the muscles will appear on the ECG
recording as noise.
7 Press the Power button on the ES-100 electronic stethoscope so that the blue power light on
the bell of the stethoscope is lit.
Procedure
1 Click on the Record button, located on the upper right side of the LabScribe Main window.
The signal should begin scrolling across the screen.
2. Click on the AutoScale button at the upper margin of the ECG channel.
• If the signal on the ECG channel is upside down when compared to trace, click on
the downward arrow to the left of the channel title and select the Invert function.
• If a larger signal is required, the electrodes should be moved from the wrists to the
skin just below each clavicle.
3. Press the Power button of the ES-100 electronic stethoscope to power it on. The blue
power light should be lit.
Note: The ES-100 electronic stethoscope automatically shuts off after 2 minutes. Push the
Power button to turn the stethoscope back on.
5.8
4
Place the bell of the EM-100 electronic stethoscope on the upper margin of the left side of
the chest.
• Use firm pressure to hold the bell against the skin. Listen for the heartbeat.
• If the “lub dub” sound of the heart beat is not heard clearly, move the stethoscope slightly
until you can hear audible heart sounds.
5. Click on the AutoScale button at the upper margin of the Stethoscope channel.
6. When you have a suitable trace, type <Subject’s Name> Resting ECG in the Mark box to
the right of the Mark button. Press the Enter key on the keyboard to attach the comment to
the data. Record for a minute or two.
7 Click Stop to halt recording.
8 Select Save As in the File menu, type a name for the file. Choose a destination on the
computer in which to save the file, like your lab group folder. Designate the file type as
*.iwxdata. Click on the Save button to save the data file.
5.9
Data Analysis
1. Scroll through the recording and find a section of data with four to six good ECG cycles and
heart sounds in succession. Four adjacent ECG-heart sounds cycles can also be selected
by:
• Placing the cursors on either side of a group of four complete ECG cycles.
• Click the Zoom between Cursors button on the LabScribe toolbar to expand the segment
with the four selected ECG cycles to the width of the Main window. Click on the
Analysis window icon in the toolbar
2
Look at the Function Table that is above the uppermost channel displayed in the Analysis
window. The names of the mathematical functions used in the analysis, V2-V1 and T2-T1,
appear in this table. The values for V2-V1 and T2-T1 from each channel are seen in the
table across the top margin of each channel.
3 Once the cursors are placed in the correct positions for determining the amplitudes and the
beat period on each ECG cycle, the values of these amplitudes and the time interval can be
recorded in LabScribe by typing their names and values directly into the Journal.
4
Place the cursors at the locations used to measure the amplitudes and period of the ECG
cycle and the heart sounds intervals.
5 Use the mouse to click on and drag the cursors to specific points on the ECG recording to
measure the following:
• The average durations of the P wave, the R wave, the T wave, PQ interval, ST segment,
average beat period in seconds/beat, heart rate in beats/minute.
Heart Rate (beats/minute) = 60 seconds/minute
# seconds/beat
• The R-Lub Interval, which is the time interval between the peak of a R wave and the
onset of the first heart sound or “lub”
• The T-Dub Interval, which is the time interval between the peak of a T wave and the
onset of the second heart sound or “dub”. Record the value for T2-T1 of either channel.
Measure this time interval for two additional ECG cycles.
There are several methods that you can use to determine the heart rate(using the graph
Paper)
Method #1:
 Examine the distance between QRS complexes and determine if the peaks
(RR intervals) are regularly spaced. If so, count the number of small squares from one
R wave to the next R wave. Divide that number into 1500 to determine the heart
rate(bpm).
Heart Rate (bpm)
=
# small squares
1500
5.10
Method #2
 Locate an R wave on a bold line. If the next R wave (to the right) is separated
from it by:




one large squares (= 5 small squares), the heart rate is 300 BPM (300/1)
two large squares, the heart rate is 150 BPM (300/2)
three large squares, the heart rate is 100 BPM (300/3)
four large squares, the heart rate is 75 BPM (300/4) and so on
Heart Rate = 72 bpm
Activity 2
Heart Rate = 37 bpm
Measuring Arterial Pressure
When the ventricle ejects a stroke volume into the elastic arteries, the arteries stretch and
pressure (pulse) waves are created. Blood pressure is defined as the pressure that blood
exerts against any unit area of the walls of blood vessels or a chamber of the heart.
Physiologists measure the pressure of body fluids, including blood, in units called millimeters
of mercury (mmHg), and they use a measuring device called a manometer. A
sphygmomanometer is a manometer with an air cuff attached to the reservoir; it can be used
to measure the changing blood pressure associated with the pulse.
You will learn to measure the systolic arterial pressure (the pressure in the arteries at the
peak of ventricular contraction), the diastolic arterial pressure (the pressure in arteries during
ventricular relaxation) and the pulse rate (the number of pulses, or heart beats, per minute).
5.11
Materials
Stethoscope
Sphygmomanometer
Felt tipped pen
Watch or clock with a second hand
Resources:
Textbook:
Interactive Physiology:
page 710-711
Measuring Arterial Pressure
Proper Use of a Stethoscope:
1.
2.
3.
Clean the earpieces of the stethoscope with alcohol swabs and allow the alcohol to
dry.
Notice that the earpieces of the stethoscope are angled. The earpieces should be
angled ion a forward direction when placed into the ears for best auscultation.
Place the diaphragm of the stethoscope over the pulse point.
Proper Use of the Sphygmomanometer
1. Wash your hands. The subject should roll up their sleeves is necessary. The subject sits
down and rests their forearm on a table so that their brachial artery is level with the heart.
This is important when monitoring blood pressure, as blood pressure is proportional to
height.
2. Check the cuff of the stethoscope for trapped air by compressing it against the laboratory
table.
3. Wrap the cuff around the subject’s arm, just above the elbow, with the inflatable area on
the medial arm surface. If the cuff is marked with an arrow, the arrow should be
positioned over the brachial artery. Secure the cuff by tucking the distal end under the
wrapped portion or by bringing the Velcro pieces together. Leave enough room to slide
two fingers between the arm and the cuff.
4. Palpate the brachial pulse and mark its position with a felt tipped pen.
5. Put on a stethoscope and place the diaphragm over the brachial pulse point.
5.12
6. Listen to the brachial pulse and inflate the cuff to about 10 mmHg above where you heard
the last sound (160 mmHg maximum). Slowly release the pressure valve (at about a
5mmHg/sec rate). As the pressure in the cuff gradually drops to levels between systolic
and diastolic pressures of the artery, the blood is pushed through the compressed artery in
a turbulent flow pattern. Under these conditions, the blood is mixed, and the turbulence
sets up vibrations in the artery that are heard as sound in the stethoscope. These sounds
are known as the sounds of Korotkoff.
The sounds are divided into five phases, based on the loudness and the quality of
the sounds:
5.13
Phase 1:
a loud, clear tapping sound is evident; it increases in intensity as the cuff is
deflated
Phase 2:
A succession of murmurs can be heard. Sometimes the sounds seem to
disappear during this time, which may be the result of inflating or deflating the
cuff too slowly.
Phase 3:
A loud, thumping sound similar to that of Phase 1, but less clear, replaces the
murmurs.
Phase 4
A muffled sounds abruptly replaces the thumping sounds of Phase 3.
Phase 5
All sounds disappear.
7. Watch the pressure gauge as you listen for the first soft, clear sounds of blood
squirting through the partially occluded artery. Note the pressure at which you hear these
sounds – this is the systolic arterial pressure.
8. As you continue to deflate the cuff, you will hear an increase in the intensity of the sounds,
then a muffling of the sound. The pressure at which the sound becomes muffled is
referred to as the first diastolic end point and the pressure reading at which the sound
disappears is referred to as the second diastolic end point. Which point to use if
controversial – select one of these points and be consistent in your use during these
experiments. You may also record both points (eg, 115/76/74 would mean that the
systolic pressure is 155, the first diastolic end point is 76 and the second diastolic end
point is 74).
Note:
1. Never keep the cuff inflated for more than one minute. If you have trouble getting a
blood pressure reading, deflate the cuff and wait one or two minutes before trying again.
5.14
Checklist
1.
2.
5.15
____
Electrocardiography
Measuring Baseline Arterial Pressure and Pulse Rate
______
Baseline Arterial Pressure
_______
Pulse Rate
PreLab Questions
Score:
_____________________
1. List the structures of the cardiac conduction system starting with the SA node:
SA node
___________________
_________________
_____________________
_______________________
2. Match the following with its description:
a.
b.
P wave
P-R interval d.
c.
T wave
QRS complex
f.
e.
S-T segment
Q-T interval
_____ represents ventricular repolarization
_____ time from the onset of atrial depolarization to the onset of ventricular depolarization
_____ represents atrial depolarization
_____ time from the end of ventricular depolarization to the onset of ventricular repolarization
_____ represents ventricular depolarization
_____ time from the onset of ventricular depolarization to the end of ventricular repolarization
3.
How many small blocks on the horizontal axis ECG tracing represent 1 second (assume that
the chart speed is 25 mm/second)?
____________________
4.
Why is it important to remain still while ECG recordings are made? _________________
______________________________________________________________________
______________________________________________________________________
5.
Why isn’t there a wave on a normal ECG tracing that represents atrial repolarization?
______________________________________________________________________
______________________________________________________________________
______________________________________________________________________
6.
What might a longer than normal P-R interval indicate?
_______________________
______________________________________________________________________
______________________________________________________________________
7.
5.16
What variable does a plethysmograph measure?
_____________________________
Lab Activities Worksheet
Name:
_____________________
Week 5 Lab
1.
Attach the ECG tracings that you recorded during the laboratory using a glue stick. Select
the best lead and label a P wave, a QRS complex, the P=R interval;, the Q-T interval and
the T wave. Also, note any unusual findings.
a.
Baseline recording:
Indicate the:
P wave duration:
______
P-R (P-Q) interval duration: _______
QRS complex duration: ______
Q-T interval duration: _______
T wave duration:
Heart rate:
______
_______
Indicate any abnormal values; what should these values be?
________________________________________________________________
________________________________________________________________
________________________________________________________________
5.17
b.
After Exercise/Recording
Indicate the:
P wave duration:
______
P-R(P-Q) interval duration: _______
QRS complex duration: ______
Q-T interval duration: _______
T wave duration:
Heart rate:
______
_______
What changes were observed (compared to the baseline recording)? Explain why these
changes occurred, in physiological terms.
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
___________________________________________________________________
18
5.18
Attach a trace of the ECG and heart sounds
Data Tables
2.
Proper Use of the Sphygmomanometer (include units of measurement):
Subject #1:
__________________________________
Systolic Pressure
Diastolic Pressure
Pulse Rate
Trial 1
Trial 2
3.
5.19
Show your homework assignment for IWORX to your lab instructor and obtain their
signature: __________