Download EKG

Wayne_sp2017
EKG and Arterial Pulse Pressure
EKG
Purpose: This exercise is designed to familiarize the student with taking an EKG and observing the
phenomenon known as the Mammalian Diving Reflex.
Performance Objectives: At the end of this exercise the student should be able to:
1.
Take an EKG of another person using the stand limb leads and IWORX equipment.
2.
Explain and demonstrate the Mammalian Diving Reflex.
3.
Calculate heart rate given the duration of the cardiac cycle.
4.
Identify the P, QRS, T wave forms of an EKG.
5.
Describe what each wave form of the EKG represents.
6.
Calculate a cardiovascular index.
Background
Activity stimulates the heart to contract more vigorously than it does when the body is at rest. The EKG
(electrocardiogram) sensor measures cardiac electrical potential waveforms (voltages) produced by the
heart as its chambers contract. The EKG does not directly measure of heart muscle activity. A
comparison of the EKG measured during rest and the EKG measured after mild exercise show the
changes that take place in the heart cycle due to activity.
The Electrocardiogram
R
P Wave
T Wave
Q
S
QRS Complex
The part of the EKG (electrocardiogram) before any measurement is taken is called the baseline.
The first deviation from the baseline (isoelectric point) in a typical EKG is an upward pulse following by
a return to the base line. This is called the P wave and it lasts about 0.04 seconds.
1
Wayne_sp2017
After a return to the baseline there is a short delay while the heart’s AV node depolarizes and sends a
signal along the atrioventricular bundle of conducting fibers (Bundle of His) to the Purkinje fibers,
which bring depolarization to all parts of the ventricles in a wave that is almost simultaneous.
When the AV node depolarizes there is a downward pulse called the Q wave. Shortly after the Q wave
there is a rapid upswing of the line called the R wave followed by a strong downswing of the line called
the S wave and then a return to the baseline. These three waves together are called the QRS complex.
This complex is caused by the depolarization of the ventricles and is associated with the contraction of
the ventricles.
Next there is an upward wave that then returns to the base line. This upward pulse is called the T wave
and indicates repolarization of the ventricles.
The sequence from P wave to T wave represents one heart cycle. The number of such cycles in a minute
is called the heart rate and is typically 70-80 cycles (beats) per minute at rest.
P-R interval... 120-200 milliseconds (0.120 to 0.200 seconds)
QRS interval... under 100 milliseconds (under 0.100 seconds)
Q-T interval... under 380 milliseconds (under 0.380 seconds)
A.
Activity: EKG and Finger Pulse: Baseline Recordings
The IWorx system will be used to record individual EKG’s and finger pulses. Each student
should make a baseline recording of their own EKG and finger pulse.
Each student should only use ONE set of electrodes for EKG, do not remove
them until you are finished with this exercise
1.
The equipment should be set up and preprogrammed for you.
2.
Prepare the subject for recording by having them remove all jewelry from wrists and
ankles. Then swab the ventral surface of each wrist and an area on the left leg just above
the ankle with an alcohol swab. You will only be using three of the leads.
3.
Place the plethysmograph (PPG) on the volar surface (area of fingerprint) of the distal
segment of the index or thumb finger and wrap the Velcro to attach the unit firmly to the
end of the finger.
Plethysmograph can be used to record changes in blood volume as the arterial
pulse expands and contracts the microvasculature.
4.
Have the subject to sit quietly with hands in their lap
5.
Click <Record> and, if needed, <AutoScale> in the channel two title area
2
Wayne_sp2017
6.
You should see a rhythmic EKG tracing and pulse appear on the screen if the trace is
upside down, click <Stop> and switch the positive and negative electrode leads or right
click and <invert>. If a cleaner signal is required, the electrodes should be moved
from the wrists to the area immediately below each clavicle and the ground next to
the umbilicus.
7.
When you are getting a suitable trace, type the “’subjects name’ and ‘resting’” and press
Enter on the keyboard.
8.
Click <stop> to halt recording
9.
Proceed to the data analysis section of the exercise
8.
Proceed to the data analysis section of the exercise
9.
Each student should print a copy of their resting EKG, label the major waves on their
EKG and paste one in the indicated space.
10.
To save a picture of the EKG: Go to file, export and save as Jpeg on a flash drive or
desktop. Email the picture to yourself and then print at home or on the lab printer. If the
picture is placed in a word document, it can be resized to fit the indicated space.
Place Tracings Here
3
Wayne_sp2017
B.
Determining heart rate.
1.
Determine the heart rate as follows:
Heart rate
=
(beats / minute)
60 sec./min.
time interval between successive
intervals in seconds. (R-R interval)*
*This is the heart rate at one moment in time, for a more reliable
estimation of heart rate take the average of 10, R-R intervals.
Heart Rate (EKG) using 1, R-R interval: ________________
Heart Rate (EKG) using 10, R-R intervals: ______________
Using the formula above, calculate heart rate using two peaks from the
pressure waves of the PPG, or again for a better estimate use the average
of 10 wave forms.
Heart Rate (PPG) using 1, R-R interval: _______________
Heart Rate (PPG) using 10, R-R intervals: ______________
2.
Pick one complete cycle (Heart Beat) and calculate the time difference
between the generation of a heart beat and the actual pulse (PPG).
1.
Press the 2-cursor icon and place one cursor on the peak of the
QRS wave in channel1
2.
Place the other curser in the peak of the finger pulse in window #2
3.
Find the time difference in the T2-T1 window; this is a rough
estimate of the time it took for the pressure pulse generated by the
heart to reach the artery in your finger
Time Difference: _________________
3.
Let the EKG run for approximately 10 seconds and watch for a normal
rhythm (If an arrhythmia is present, call your instructor to verify). Also
observe the relationship between atrial and ventricular rhythms.
_____________________________________________________________
4
Wayne_sp2017
4.
_____________________________________________________________
Record the EKG and pulse of a student lying down after resting quietly for a few
minutes. Then have the student stand quickly. Observe differences in the heart
rate. Explain.
HR (Lying Down): _____________ HR (Standing): ________________
__________________________________________________________________
__________________________________________________________________
__________________________________________________________________
5.
Describe the effect of exercise on the EKG. Make sure the electrodes are
securely placed, disconnect the leads from the at the limb electrodes and allow
the subject to engage in several minutes of vigorous exercise, preferably by
placing one foot on a chair and raising and lowering the body repeatedly.
Rapidly return the subject to the supine position; reconnect the limb leads. Why
is speed essential in re-connecting the subject to the EKG?
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
C.
Calculating Intervals from the EKG
1.
Determine the P-Q interval from your EKG and record the time.
2.
Determine the Q-T interval from your EKG and record the time.
3.
Determine the R-R interval and record the time in the table below.
Item
P - Q interval
Q -T interval
R -R interval
Rest (sec)
Exercise (sec)
Compare your values for the P-Q, and Q-T intervals for the EKG at rest to the values for the P-Q,
and Q-T intervals for the EKG after mild exercise. How do the time intervals for the EKG after
mild exercise compare to the time intervals for the EKG at rest? Explain the differences.
5
Wayne_sp2017
_______________________________________________________________
_______________________________________________________________
_______________________________________________________________
What percent of the time are the ventricles contracting? Use the QT interval to help you with the
calculation.
______________________________________
6
Wayne_sp2017
Part III: The Mammalian Diving Reflex
Using a student volunteer, the instructor will demonstrate the Mammalian Diving Reflex
A sphygmomanometer, stethoscope, IWORX System alcohol swabs, and volunteer are needed for the
test. A pan of ice water, pan of room temperature water and towels are needed, along with all the
previously mentioned materials, to demonstrate the diving reflex.
Initially, a three lead EKG is performed on a subject that is sitting and resting with their arms resting on
their thighs breathing normally. For the diving reflex, the subject is asked to hold their breath and then
immerse their entire face (including forehead) into the pan of ice water while continuing to hold their
breath as long as possible. The EKG and blood pressure “before and after” results are recorded.
Heart Rate at end of breath holding in warm water: _____________
Heart Rate at end of breath holding in cold water: ______________
Part IV: Harvard Step Test
INTRODUCTION
The Harvard Step Test was developed in the Harvard Fatigue Laboratory in World War II
to screen men for physical fitness and to evaluate the progress of physical training programs. The
Harvard Step Test measures general endurance or physical condition.
The test consists of having the subject step up and down on a bench 20" high (16" for
women) for 5 minutes, if possible and then measuring heart rate recovery during a post-exercise period.
Subjects should stop if they feel that they cannot continue1. This exercise should only be done by those
individuals who are in good physical health.
PROCEDURE
1.
The subject stands in front of a bench of appropriate height. An observer stands behind
the subject. The subject steps up and down on the bench at a rate of 30 steps (all the way
up and down constitutes one step) per minute for a maximum of 5 minutes. The observer
should watch the subject to insure the subject maintains the correct pace. The observer
should also watch the subject to prevent accidental falls.
2.
When the subject stops at the end of 5 minutes or sooner if the subject cannot keep pace,
the subject should relax while the observer gets ready to take the subject's pulse. The
duration of the exercise should also be noted.
7
Wayne_sp2017
3.
Taking the Pulse:
A.
One minute after finishing the test take your pulse rate (bpm)- Pulse 1
B.
Two minutes after finishing the test take your pulse rate (bpm) - Pulse 2
C.
Three minutes after finishing the test take your pulse rate (bpm) - Pulse 3
4.
The physical fitness index is computed from the following formula:
Index =
5.
duration of the exercise in seconds x 100
--------------------------------------------------2 (Sum of Pulse 1, Pulse 2, Pulse 3)
Interpretation of Scores:
Gender
Excellent
Above Average
Average
Below Average
Poor
Male
>90
80-90
65-79
55-64
<55
Female >86
76-86
61-75
50-60
Table Reference: McArdle W.D. et al; Essential of Exercise Physiology; 2000
6.
<50
Record your result or that of someone from the class________________.
The Harvard Step Test can be modified to equalize the work for persons of different height. If
the equipment is available, use the following adjusted bench heights:
HEIGHT
BENCH HEIGHT
less than 5'
5' to 5' 3"
5' 3" to 5' 9"
5' 9" to 6'
greater than 6'
12"
14"
16"
18"
20"
Useful References:
1. D. F. Speck, D. S. Bruce, Undersea Biomed. Res. 5(1), 9-14 (1978).
2. C. D. Moyes, P. M. Schulte, Principles of Animal Physiology. (Benjamin Cummings, 2007).
3. S. Colberg, Against all odds, toddler Gore Otteson survives a near-drowning and an hour with no heartbeat (2010). Available
at http://newsok.com/against-all-odds-toddler-gore-otteson-survives-a-near-drowning-and-an-hour-with-no-heartbeat/article/3496460 (September 2010).
4. When breathing stopped, the miracle began: 21-month-old Gore Otteson defies odds with recovery from near-drowning (2010). Available
at: http://www.gunnisontimes.com/index.php?content=C_news&newsid=6715 (September 2010).
5. J. Blevins, Watery tragedy averted as Lakewood toddler’s life “miraculously” revived (December 2010). Available
at: http://www.denverpost.com/news/ci_16852219
8