BIO2350L_Lab_8

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California Polytechnic State University, Pomona *

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Apr 3, 2024

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CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Lab 8: Electrocardiogram Learning Outcomes By comple<on of this lab students will be able to: 1. List the parts of the conduc<on system and explain how the system func<ons. 2. Define cardiac cycle, systole, and diastole. 3. Iden<fy the events in a normal ECG. 4. Use Biopac electrodes to record an ECG. 5. Analyze an electrocardiogram to measure the dura<ons of ECG events. 6. Test the effects of different physical tasks on the electrical ac<vity of a human heart. 7. Iden<fy and correct examples of unclear communica<on in results tables. 8. Compare ECG results with predicted ranges. 9. Discuss the implica<ons of ECG test results. 10. Relate ECG events to atrial and ventricular depolariza<on and repolariza<on. 11. Relate ECG events with ventricular systole and diastole. 12. Explain the effects of the parasympathe<c and the sympathe<c nervous system on heart rate. 13. Explain the purpose of ECG tes<ng. Background An electrocardiogram is a graph of the electrical ac<vity, consis<ng of depolariza<ons and repolariza<ons, of the heart over <me. The elements of an electrocardiogram are waves and segments . Segments are parts of the electrocardiogram where there is no electrical ac<vity, thus segments are measured along the baseline, also called the isoelectric line . Waves are parts of the electrocardiogram where the heart is depolarizing or repolarizing. The electrocardiogram can also be divided into intervals , the sums of at least one wave and one segment. See the "EKG Introduc<on" handout for more informa<on. Note that this introduc<on provides predicted values for the parts of the electrocardiogram and will need to be referenced to compare results and conclude if a subject is healthy. The electrocardiogram is important because it can be used to diagnose heart disease, the leading cause of death in the US.

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Materials and Equipment Materials: 1. Electrode pads x3 Equipment: 1. BioPac Electric Lead Set 2. Yoga mat Lab Safety One condi<on for this lab is exercise. Do not par<cipate as the test subject for this lab if you have a heart condi<on that contraindicates exercise. Methods 1. For this ac<vity, students must work in groups of at least 2 people. One person will be the subject, and the other person can operate the computer system. 2. Obtain 3 electrodes for your subject and place them as seen in Figure 1 . Place one electrode slightly below your right wrist and connect it to a white electrode lead. Place the next two electrodes on the medial surface of each leg, right above the ankle for both legs. Abach the black electrode lead to the electrode on your right leg. Abach the red electrode lead to the electrode on your le2 leg. Figure 1 . Electrode Arrangement. 3. Each subject must conduct his/her own calibra<on in a supine posi<on (lying down relaxed and completely stretched out as seen in Figure 2 .

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Figure 2 . Supine Position. 4. Check that the BioPac soeware is opened to L05 Electrocardiography (ECG) I. If not, please ask your TA to help locate the correct lesson. 5. Begin calibra<on when your subject is fully relaxed with their eyes closed. Locate “Calibrate” on your screen and follow the direc<ons. Your screen will look like Figure 3 . Don’t worry if the wave paberns are diﬃcult to see. You can zoom in using the magnifying glass tool to visualize your ECG results more clearly. Figure 3 . Calibration Screen. a. Your calibra<on data should look like Figure 4 . You should see a consistent and recognizable ECG waveform with a baseline around 0 mV. Note that the T wave is oeen very subtle and some<mes can’t be differen<ated from noise. The P and RST waves are typically clearer.

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CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Figure 4 . ECG Wave Forms Recorded During Calibration. b. If the data is noisy or ﬂatline, check all connec<ons to the BioPac unit. If the ECG displays baseline drie verify that the electrodes are making good contact with the skin and that the leads are not pulling on the electrodes and make sure your subject is in a relaxed posi<on. Redo calibra<on if necessary. 6. Now you are ready to start the experiment. The subject should remain in a supine posi<on, as this will be the first condi<on to be tested. If the BioPac skips the supine condi<on, you can use the data collected during your calibra<on. When you are ready to record, click “Record” and record for about 20 seconds, then click “Suspend.” You should see a series of consistent ECG waveforms like Figure 5. Figure 5 . ECG waveforms recorded in the supine position. a. If you are not gelng clear P, QRS, and T waves check to see if your connec<ons are secure then click “Redo.” If you have a large amount of background noise on the recording you could use electrode gel to improve the signal. 7. The next recording is made with the subject seated. Have your subject sit relaxed in a chair, keeping their arms and legs uncrossed. The subject’s hands should be placed on their legs with the palms facing upward ( Figure 6 ). When the subject is ready, start recording by clicking on “Record,” and record for 20 seconds.

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Figure 6 . Subject seated with palms facing upward. 8. The next condi<on is the Deep Breathing condi<on. For this recording, the subject stays seated. They inhale and exhale slowly for 5 back-to-back breathing cycles. If possible, subject should breathe in and out through his/her nose. The subject should communicate with the person opera<ng the computer system to no<fy the operator when inhaling and exhaling. It is suggested that the subject raise their thumb at the start of inhale and lower their thumb at the start of exhale. The operator will press the F4 bubon at the start of each inhale, and press F5 at the start of each exhale. This creates a lible triangle icon above the data field to mark the breaths. a. You can repeat the recording if the waveforms are not clear, the recording has too much background noise, or the inhale and exhale markers were not recorded correctly. 9. The last condi<on is "Aeer Exercise." For this condi<on, the subject removes the electrode leads but keeps the electrodes s<ll abached to the skin. The subject needs to exercise for 1 minute. Have one person in your group <me your subject for 1 minute while they do jumping jacks / run on the spot / do pushups or any other exercise that increases the heart rate. 10. Immediately aeer 1 minute is over, abach all electrode leads in the appropriate designa<on as before (refer to step 2) and start recording! a. Note that the heart will quickly return to a relaxed state, so it is necessary to record as quickly as possible aeer exercise. It is recommended to begin recording 15-30 seconds aeer exercise. b. There may be some electromyographical signal associated with heavy breathing post-exercise that causes baseline drie in the recording. To minimize baseline

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA drie from heavy breathing, concentrate on taking shallow breaths rather than deep breaths. 11. Your recording should last for 60 seconds this <me! Click “Suspend” aeer 1 minute. Then click “Done.” 12. Analyze the data and complete your lab worksheet. To do this you will need to go back and use your I-bracket tool to measure either change in <me (Delta T), peak-to-peak (P- P), or beats-per-minute (BPM) values. It will be helpful for you to zoom in on your results using the magnifying glass tool, so the waveforms are easy to dis<nguish ( Figure 7 ). Figure 7 . ECG data after magnification with the magnifying glass tool. 13. Bracket one R-R interval from the supine recording condi<on and choose the "BPM" measurement. Enter this value in Table 1 . Then measure two other R-R intervals for this condi<on and calculate the mean. Move to the next recording condi<ons and measure R-R intervals. 14. Use the I-bracket tool to measure the <me (Delta T) required to complete ventricular systole and diastole and enter values in Table 2 . For Ventricular Systole and Diastole measurements, the T wave reference point for the selected area is 1/3 of the way down the descending por<on of the T wave ( Figure 8 ). Figure 8 . ECG related to the electrical and mechanical events of the cardiac cycle.

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CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA 15. Measure the dura<ons in seconds of the ECG components ( Figure 8 ) and enter values in Tables 3, 4, & 5 . While the computer operator is measuring these components, another group member should open the "EKG Introduc<on" file on Canvas and compare the measured values with the predicted values in Table 5.1 . Make note of any measured values with dura<ons that are outside the normal range ( QuesEon 5 ). Also, is the condi<on "Res<ng" one of the original recording condi<ons? If not, is this an example of unclear communica<on? If so, how can you clarify the communica<on of your results?

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Results Table 1 . Heart rate for five different physiological conditions. Table 2 . Ventricular systole and diastole for two physiological conditions. Table 3 . Waves of the ECG showing measurement of three resting cycles, one post-exercise cycle, and the mean of the resting cycles. Table 4 . Intervals of the ECG showing measurement of three resting cycles, one post-exercise cycle, and the mean of the resting cycles. Table 5. Intervals of the ECG showing measurement of three resting cycles, one post-exercise cycle, and the mean of the resting cycles. CondiEon Cycle 1 (BPM) Cycle 2 (BPM) Cycle 3 (BPM) Mean (BPM) Supine 63 67.8 61.5 151.3 Seated 67.9 64.3 65.2 154 Start of Inhale 84.7 75.6 66.4 182.4 Start of Exhale 66.4 60 57.9 145.7 ARer Exercise 80.5 85 89.8 195.4 CondiEon Systole (s) Diastole (s) Supine 0.321 0.60 ARer Exercise 0.28 0.49 Wave Supine 1 (s) Supine 2 (s) Supine Supine Mean (s) Post-Exercise (s) P 0.09 0.08 0.10 0.09 0.07 QRS 0.06 0.07 0.06 0.063 0.09 T 0.23 0.25 0.22 0.55 0.16 Interval Supine 1 (s) Supine 2 (s) Supine 3 (s) Supine Mean (s) Post-Exercise (s) P-R 0.13 0.13 0.13 0.30 0.12 Q-T 0.38 0.38 0.39 0.89 0.36 R-R 0.86 0.88 0.95 2.06 0.58 Segment Supine 1 (s) Supine Supine 3 (s) Supine Mean (s) Post-Exercise (s) P-R 0.02 0.02 0.02 0.047 0.04 S-T 0.11 0.11 0.12 0.26 0.20

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA Conclusion 1. What changes in heart rate did you see between the different condi<ons you tested in the lab today? Refer to your data from Table 1 . Describe the physiological mechanism(s) causing these changes. The changes in heart rate observed during the lab tests this week showed variaEons in the mean BPM values across different physiological condiEons. We found that the heart rate was highest aRer exercising, with a mean BPM of 195.4, which makes sense as the body needs more oxygen during exercise. On the other hand, the heart rate was lowest at the beginning of exhaling, with a mean BPM of 145.7. This is because when we exhale, the body is relaxed and doesn't need as much oxygen, leading to a momentary dip in heart rate. 2. Are there differences in the cardiac cycle with the respiratory cycle? Refer to the "start of inhale" and "start of exhale” data from Table 1 . Yes, there are differences in the cardiac cycle with the respiratory cycle. As the body prepares for increased oxygen intake during the "Start of Inhale," the heart rate increases. This increase in heart rate aligns with the body's anEcipaEon of the need for more oxygen during inhalaEon. On the other hand, at the "Start of Exhale," the heart rate decreases, which is a‘ributed to the body entering a relaxaEon state as it releases carbon dioxide during exhalaEon. The changes in heart rate during different breathing phases show that our breathing and heart funcEon are closely connected to ensure that our body has suﬃcient oxygen. 3. What changes occurred in the dura<on of systole and diastole between res<ng and post- exercise? Refer to Table 2 . The changes occurred in the duraEon of systole and diastole between resEng and post- exercise, where there is a decrease in the duraEon of systole aRer exercise compared to the supine state, indicaEng that the heart is pumping blood more eﬃciently and quickly post-exercise. AddiEonally, the duraEon of diastole also decreased aRer exercise compared to the supine state, suggesEng that the heart is taking less Eme to relax and refill with blood between beats due to the increased cardiovascular demand during exercise. These changes reﬂect the dynamic adjustments in the cardiac cycle in response to varying physiological demands. T-P 0.40 0.38 0.37 0.90 0.27 Segment Supine 1 (s) Supine Supine 3 (s) Supine Mean (s) Post-Exercise (s)

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CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA 4. Compared to the res<ng state, do the dura<ons of the ECG intervals and segments decrease during exercise? Why do you think this occurs? Yes, during exercise, the duraEons of ECG intervals and segments generally decrease compared to the resEng state. This happens because physical acEvity leads to an increase in heart rate (HR) and cardiac output. The higher HR causes the heart to beat more frequently, resulEng in shorter intervals between each heartbeat on the ECG. As the heart works harder during exercise to meet the body's oxygen demand, the intervals and segments on the ECG shorten to reﬂect the faster electrical acEvity and more eﬃcient funcEoning of the heart under increased workload. 5. Compare your ECG data ( Tables 3-5 ) to normal ranges (Introduc<on to the Electrocardiogram Reading, Table 5.1). Iden<fy any of your test subject's values that were outside the normal ranges. Upon comparing the ECG data from Tables 3-5 to normal ranges, there were several values from the post-exercise cycle outside the normal ranges. Specifically, the QRS duraEon of 0.09s in Table 3 exceeded the normal range. Also, in Table 4, the R-R interval of 0.58s in the post-exercise cycle was lower than the normal range, indicaEng a faster heart rate post-exercise. In Table 5, the S-T interval of 0.20s in the post- exercise cycle was also outside the normal range. These values suggest that the subject's heart underwent some changes during and aRer exercise that were not typical ECG measurements. 6. Did your test subject's cardiovascular system func<on normally? If any of your subject's ECG values were outside the normal range, list a few possible condi<ons that could cause these results and explain which condi<on you think is most likely. Based on the ECG data with values outside the normal ranges post-exercise, it suggests that the test subject's cardiovascular system may not have funcEoned enErely normally during and aRer exercise. Possible condiEons that could cause these results include myocardial ischemia, electrolyte imbalances, or cardiac arrhythmias. Among these, myocardial ischemia seems most likely as the S-T segment changes observed post-exercise can indicate insuﬃcient blood ﬂow to the heart muscle during physical exerEon, leading to abnormal ECG readings. 7. To beat, the heart needs three types of cells. Describe the cells and their func<on. a. The heart needs Rhythm generator, also known as the sinoatrial (SA) node. These cells are in charge of starEng the electrical signals that make the heart

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA beat in a steady rhythm. The SA node is like a natural pacemaker for the heart, making sure it beats at the right speed. b. The heart requires conducEng cells, such as the atrioventricular (AV) node and a bundle of His. These cells are responsible for conducEng electrical signals generated by the SA node throughout the heart to ensure that the atria and ventricles contract in sync. c. The heart's pumping acEon depends on contracEle cells (myocardial cells) that make up the heart's muscle Essue. These cells are responsible for contracEng and relaxing to pump blood throughout the body. The contracEle cells work together to help maintain healthy circulaEon and supply the body's Essues with oxygen and nutrients. 8. List the components of the cardiac conduc<on system in the correct order star<ng at the pacemaker cells. (Include the anatomical name for the pacemaker of the heart). a. Sinoatrial (SA) node (pacemaker cells) b. Atrioventricular (AV) node c. Bundle of His (atrioventricular bundle) d. LeR bundle branch e. Right bundle branch f. Purkinje fibers g. Ventricular contracEle cells 9. Describe three cardiac effects of increased sympathe<c ac<vity, and of increased parasympathe<c ac<vity. Increased sympatheEc acEvity 1. Faster heart rate: SympatheEc acEvity speeds up the heart rate to prepare the body for acEon. 2. Stronger heart contracEons: It increases the force of heart contracEons, pumping more blood with each beat. 3. DilaEon of blood vessels: SympatheEc acEvity can widen blood vessels, increasing blood ﬂow and oxygen delivery to Essues. Increased parasympatheEc acEvity 1. Slower heart rate: ParasympatheEc acEvity slows down the heart rate during rest and relaxaEon.

CALIFORNIA STATE POLYTECHNIC UNIVERSITY, POMONA 2. Weaker heart contracEons: It decreases the strength of heart contracEons, leading to a gentler heartbeat. 3. ConstricEon of blood vessels: ParasympatheEc acEvity can narrow blood vessels, reducing blood ﬂow and oxygen supply to Essues. 10. In the normal cardiac cycle, the atria contract before the ventricles. Where is this fact represented in the ECG? During a normal cardiac cycle, the atria contract before the ventricles. This is shown as a "P" wave on an ECG reading. The P wave represents the electrical acEvity responsible for the atria's contracEon. ARer the P wave, there's a li‘le pause at the atrioventricular (AV) node before the QRS complex. The QRS complex represents the ventricles contracEng. This shows that the ventricles contract aRer the atria. So the sequence of events in an ECG reﬂects the order in which the atria and ventricles contract during a heartbeat. 11. What is meant by “AV delay” and what purpose does the delay serve? The AV delay is the quick pause in the heart's electrical system at the atrioventricular (AV) node. This delay gives the atria some Eme to contract before the ventricles do so that the ventricles can fill up with blood before they start contracEng. This process makes sure that the heart pumps blood eﬃciently throughout the body by coordinaEng the Eming of atrial and ventricular contracEons. 12. What does the isoelectric line of the ECG represent? The isoelectric line on an ECG represents the baseline or zero voltage level when there is no electrical acEvity occurring in the heart. It serves as a reference point for interpreEng the electrical signals generated by the heart during the cardiac cycle. It also helps idenEfy deviaEons from the baseline, such as the presence of abnormal rhythms or changes in the heart's electrical acEvity. 13. What is the purpose of an electrocardiogram? An electrocardiogram (ECG) is a test that records the electrical acEvity of the heart. It helps healthcare providers diagnose heart condiEons such as arrhythmias, heart a‘acks, and abnormaliEes in the heart's rhythm and structure. Doctors analyze the pa‘erns and waveforms on the ECG to assess the heart's overall health, detect irregulariEes, and determine the best course of treatment for paEents with heart- related issues.

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BIO2350L_Lab_8

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