Physiology 1 electrocardiogram lab (ECG/EKG)



LAB 6A: ECG Electrocardiography (ECG)In this lab you will explore the response of the heart to a variety of stimuli. Begin this activity by setting up your subject to record a resting ECG. You will be looking for changes in the hearts’ activity in response to the different treatments. There are many features of the ECG that may vary, including the intervals between phases of the cardiac cycle, the amplitude of the recording corresponding to the contractility, and the frequency of beats (heart rate or pulse rate) (Figure 1).286448585725ECG WavesP Atrial depolarization (<110ms)QRS Ventricular depolarization (50-100ms)T Ventricular repolarization (around 160ms)ECG Intervals/SegmentP-R Atrial depolarization and systole; AV nodal delay (120-200ms). Sometimes referred to as P-Q interval. Beginning of P wave to beginning of QRS complex.Q-T Ventricular depolarization, systole, and repolarization (<350ms). Beginning of QRS to end of T wave.T-P Ventricular diastole (~250ms). TP segment is from the End of T wave to beginning of next P wave.00ECG WavesP Atrial depolarization (<110ms)QRS Ventricular depolarization (50-100ms)T Ventricular repolarization (around 160ms)ECG Intervals/SegmentP-R Atrial depolarization and systole; AV nodal delay (120-200ms). Sometimes referred to as P-Q interval. Beginning of P wave to beginning of QRS complex.Q-T Ventricular depolarization, systole, and repolarization (<350ms). Beginning of QRS to end of T wave.T-P Ventricular diastole (~250ms). TP segment is from the End of T wave to beginning of next P wave.Figure 1. ECG and the Cardiac CycleMany pathologies can be discerned from an ECG. An enlarged P wave is a sign that the atria are enlarged, usually as a result of constriction of the bicuspid valve. If the atria contract too frequently, a condition known as atrial flutter, many P waves will precede the QRS complex. The P wave will be absent when the sinoatrial (SA) node is not functional or during atrial fibrillation, a condition resulting in rapid, incomplete contractions of the atria. An abnormally long P-R interval indicates delayed conduction through the atrioventricular (AV) node, which can have many causes such as a history of atherosclerotic heart disease or rheumatic fever. An enlarged Q wave or elevation in the S-T segment between the S and T waves is often associated with a myocardial infarction, commonly referred to as a heart attack. An enlarged R wave generally indicates enlarged ventricles. The T wave may be flattened if there is an imbalance in K+ or if the heart is not receiving enough oxygen. During acute heart attacks or electrical shock, ventricular fibrillation can occur, which results in bizarre irregular ECG deflections.To record an ECG, follow these steps:Place disposable electrodes on clean skin as follows:WHITE electrode lead to Right WristBLACK electrode to Right AnkleRED electrode to Left Ankle Connect the SS2L electrode lead cable to the Biopac unit Channel 1.From the computer menu choose Lesson 5 from the BioPac menu and setup. With subject laying down in supine position, press the Record button and let the Biopac unit record for 20-60 seconds. If there is a problem during the recording press redo to record again. Set Channel 1 to ?T to measure the change in time. Use the I-beam tool to highlight and measure the various ECG intervals as follow:P-R by highlighting the beginning of P wave to the beginning of the QRS complexQ-T by highlighting from the beginning of QRS to the end of the T waveQRS by highlighting the QRS complex from the beginning of Q to the end of ST-P by highlighting the end of the T wave to the beginning of the following P waveSet another Channel to BPM to get the heart rate. Select one cardiac cycle (e.g. by highlighting the R peak of one QRS wave to the following R peak) and measuring the beats per minute. Record an ECG (~60 seconds each activity):Supine: Record the ECG while the test subject is laying down and relaxed.Biofeedback: Have the subject concentrate on lowering heart rate while watching the ECG recording; note any changes over that time interval.Exercise: Keep disposable electrodes attached but disconnect SS2L lead cable. Have the subject exercise for 5 minutes (e.g. jogging) then immediately reconnect the lead and record. Name: Frankie GuevaraGroup Members: Lisa Reyes, Alexandrea Ruiz, Anusara Thawpinit, and Christy Balderrama Measure the various parts of the ECG in seconds and enter in Table 1 below. Be sure to record the units for ?T (e.g. sec or msec) and convert all to seconds so values can be compared.Test Subject: FrankieTable 1: Electrocardiography Measurements ?T (seconds)ActivityP-R Q-T QRS complexT-PHeart rateSupine (resting)0.064000.365000.143000.5400067.26457Biofeedback0.127000.412000.111000.4920067.34006Exercise0.151000.258000.670000.3450084.26966Lab 6A Assignment: ECG AnalysisWhat was your hypothesis? Which part(s) of the ECG did you predict would change the most? Include your reasoning (justification) for this prediction.Based on the activity, the exercise will have the most change in the ECG. Since the heart rate will be faster because of physical activity there will be a smaller measurement for each section of the ECG resulting in change in seconds for the electrocardiography measurements. Looking at the data in Table 1, which part(s) of the ECG changed the most (P-R, Q-T, etc..)? Evaluate your hypothesis. Include a discussion of these various sections of the ECG to describe what is taking place within the heart (e.g. depolarization of ventricles, etc..) The greatest change in the ECG was in the QRS complex. Based on these changes, the hypothesis can be accepted. Results from the supine and the biofeedback are exceptionally lower than the exercise results of the QRS complex. The QRS complex is the section of the ECG where ventricular depolarization occurs. This quickly leads to the contraction of the ventricles and ejection of blood out of the heart and into the large arteries exiting the heart. Using the supine resting heart rate as a control baseline for normal heart rate, determine if the test subject was able to lower his or her HR using biofeedback? If so, explain what technique your test subject used to do this. If not, explain why you think he/she wasn’t able to do this.Using the supine resting heart rate as a control to compare it to the biofeedback the test subject was not able to lower his heart rate. The heart rate essentially stayed the same. Being that I was the subject it was difficult to raise my heart rate because I found that I could not get relaxed enough, plus I started to think about my school, work, and my personal life. Compare the supine ECG values to the post-exercise values. Which intervals and/or segments changed most significantly? Include a detailed discussion of specific changes (include numerical values) to support your findings and analysis. Discuss your group’s heart rate data and use your knowledge of physiology to explain how and why these changes were seen. Address your hypothesis and explain the overall significance of the changes seen in cardiac paring the supine ECG values to the post-exercise values the most change occurred in the PR and TP segment, and the QRS complex. The changes would be in numerical values. For example, the supine value for the PR segment is 0.06400 and the post-exercise value is 0.15100. Then, the supine value for the TP segment is 0.54000 which then dropped after the post-exercise to 0.34500. Finally, the supine value for the QRS complex is 0.14300, it then increased to 0.67000 after post-exercise. Discussing the heart rate for the supine value is 67.26457 and after exercising it is 84.26966. There is an increased heart rate due to the sympathetic agents. Catecholamine’s come in an increase ion flow through If and Ca2+ channels. This causes the SA node to undergo depolarization faster which eventually increases heart rate or cardiac output. Comment on the lab exercise. What did you learn? Were there any unusual findings or challenges with the ECG measurements or BioPac equipment while gathering data. Do you have any recommendations for improving the lab?In this lab exercise I learned vital elements to an ECG that will help me when I pursue my career as a registered nurse. But, overall I learned what a normal ECG looks like. For every P wave, there is a QRS complex and a T wave. There were not any challenges when reading the ECG because of prior instructor help and explanation before starting the lab. No recommendations for improving the lab. ................
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