Lab 5 - Cardio ECG and PFT

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Dec 6, 2023

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© 2023 George Crocker 1 Lab 5: Cardiovascular Responses to Exercise, ECG and Pulmonary Function Tests There will be three stations in this lab : 1. Cardiovascular responses to acute exercise 2. Electrocardiography 3. Pulmonary function testing CARDIOVASCULAR RESPONSES TO ACUTE EXERCISE Heart rate (HR) is commonly measured during exercise to assess exercise intensity. HR is easily measured via commercial HR monitors. However, HR can also be assessed by palpation ( i.e., feeling ) of various pulse points. Another measure of cardiovascular function is arterial blood pressure. Arterial blood pressure is measured by auscultation ( i.e., listening ) using a stethoscope and a blood pressure cuff (also known as a sphygmomanometer ). Blood pressure represents the driving force for blood flow in the circulatory system. Blood pressure is the product of blood flow and total peripheral resistance (Pressure = Flow x Resistance). Much like a garden hose you can increase the pressure ( how far the water will shoot out the end of the hose ) by either increasing flow ( opening the valve ) or increasing resistance ( putting your thumb over the opening ). In the circulatory system, increases in heart rate (the number of beats per minute) and/or stroke volume (volume of blood pumped with each beat) will increase cardiac output and increase blood pressure. Relaxation of smooth muscle that surrounds arterioles ( vasodilation ) will lower resistance and decrease blood pressure. Systolic blood pressure (SBP) is the pressure required to keep an artery closed when the heart is contracting. Diastolic blood pressure (DBP) is the pressure required to keep an artery closed when the heart is not contracting. Rate pressure product (RPP) is: 1. An indication rate of power output for the heart 2. An indication of the oxygen demand of the heart 3. Calculated as heart rate (HR) multiplied by systolic blood pressure (SBP) . Procedure : Select a cycle ergometer protocol for your subject. Remember that the cycle ergometer measures absolute work and will be more difficult for smaller individuals regardless of fitness level. The subject will be measured at 4 exercise intensities and at rest. Assign roles to people in your group: subject, blood pressure technician, heart rate monitor, timer/supervisor, and recorder. Predetermine the protocol and calculate the power at each exercise intensity prior to beginning. Consult your lab instructor before proceeding.

Measure the subject at rest while sitting on the bike! Subjects will exercise for 4 minutes at each of 4 exercise intensities (plus another at rest). You will record HR and systolic blood pressure every 2 min. Make sure you understand how you will be getting each data point on the table below before proceeding. Subject: Raphael Mass: 167 kg Cadence: 50 rpm Resistance (kg) Power (W) Time (min) HR (bpm) SBP (mmHg) RPP (mm Hg min -1 ) 0 0 0 2 4 6 8 10 12 14 16

ELECTROCARDIOGRAPHY Electrocardiography (ECG) is the measurement of the electrical activity of the heart . You will place four electrodes on your subject - one on each wrist and one on each ankle. Place the electrodes over soft tissue not bones. Alternatively, the wrist electrodes may be placed between the clavicle, pectoralis muscle, and anterior deltoid and the ankle electrodes may be placed between the external oblique and rectus abdominis muscles levels with the navel. Make sure you shave (if needed) and clean their skin sites with an alcohol prep pad. You may also use fine grit sandpaper after letting the alcohol evaporate! Attach the ECG wires to these electrodes after the electrodes have been placed on the subject’s skin. These four electrodes will give you six leads (or views) of the heart in the coronal plane (you would need to put on the chest electrodes to view the heart in the transverse plane [leads V 1 -V 6 ]). Figure 5.1. An example ECG. Ignore leads V 1 - V 6 as we will not put on the chest electrodes. The rhythm strip is located on the bottom (“Rhythm II”). The six leads in the frontal plane are I, II, III, aVR, aVL and aVF.

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Basic ECG interpretation : Rate : ❏ Regular or irregular? ❏ Determine rate by: ❏ Estimating the heart rate from the distance between subsequent R waves using the rhythm strip and the formula: HR (bpm) = 300/(# of boxes between R waves) ❏ Counting the number of QRS complexes on your 10-second rhythm strip and multiply by 6 Rhythm : Look at the rhythm strip and go through the following checklist: ❏ Does each ECG trace look like the others? ❏ Is each QRS complex preceded by one P wave and followed by one T wave? ❏ Is the PR interval between 0.12-0.20 seconds? ❏ Is the QRS duration less than 0.12 seconds? ❏ Does the ST segment return to baseline? Your ECG has a normal sinus ( originating from the sinoatrial node ) rhythm if you answered “yes” to all of the above questions. If not, identify which aspect was not normal for the ECG tracings you recorded. QRS axis : A 12-lead ECG has 6 leads that look at the heart in a different direction but all in the frontal plane. These 6 leads are made up of from the four limb electrodes (3 active + 1 ground electrode on the right leg, RL). Therefore, all 6 leads are calculated from the same 3 electrodes (right arm, RA; left arm, LA; left leg, LL). ● Lead I = LA - RA positive direction = 0° ● Lead II = LL - LA positive direction = 60° ● Lead III = LL - LA positive direction = 120° ● Lead aVR = RA - ½ (LA + LL) positive direction = -30° ● Lead aVL = LA - ½ (RA + LL) positive direction = 150° ● Lead aVF = LL - ½ (RA + LA) positive direction = 90°

Figure 5.2. QRS axis determination in the frontal plane. Estimate the QRS axis by finding the lead in which the QRS complex has roughly the same positive and negative deflection ( i.e., isoelectric ). The subject’s QRS axis will be perpendicular to this lead. Therefore, find the lead that is perpendicular to (90° away from) the isoelectric lead (Fig. 7.2). The QRS deflection in this lead will either positive (above the baseline) or negative (below the baseline). If it’s positive then the QRS axis points in the direction of that lead (solid line in figure 7.2). If the QRS deflection is negative in that lead, then the QRS axis points in the opposite direction of that lead (dashed line in figure 7.2). There are many physiologic and pathologic causes of QRS axis deviation. One example is hypertrophy. Pulmonary hypertension will increase the size of the myocardium on the right side of heart (right ventricular hypertrophy) and may cause right axis deviation. Systemic hypertension will increase the size of the myocardium on the left side of the heart (left ventricular hypertrophy) and may cause left axis deviation. There is also evidence that changing body position will alter someone’s QRS axis. Therefore, the position (usually lying supine) of the subject is important to note. The normal QRS axis is between -30 to 90° (see figure 7.2). Left axis deviation would be angles less than -30° and right axis deviation would be angles greater than 90°.

PULMONARY FUNCTION TESTING Pulmonary function tests (PFTs) measure how well your lungs work. Spirometry is a PFT that measures the volume and flow rates as you inhale and exhale. Spirometry is a valuable tool for diagnosing diseases of the lungs [ e.g. , asthma and chronic obstructive pulmonary disease (COPD; includes emphysema & chronic bronchitis )]. Results from spirometry tests are usually displayed in two forms: volume vs. time ( Fig. 5.3 LEFT ) and flow vs. volume ( Fig. 5.3 RIGHT ). The volume vs. time graph shows two normal breaths followed by a maximal inspiration and then a maximal expiration and then two normal breaths. The flow vs. volume graph shows a single full inspiration (below the x axis) and a single maximal expiration (above the x axis). Figure 5.3. Volume vs. time (LEFT) and flow vs. volume (RIGHT) spirographs. Abbreviations used are listed in Table 5.1. Forced vital capacity (FVC) is the largest volume of air that you can forcefully exhale after a maximal inspiration. It is the same as vital capacity only the subject is instructed to exhale as fast and forcefully as possible . Forced expiratory volume in 1 second (FEV 1 ) is the maximum amount of air you can exhale from your lungs in the first second of expiration after a maximal inspiration. The ratio of FEV 1 /FVC is the percentage of your vital capacity that you can exhale in the first second. Healthy adults should have FEV 1 /FVC around 80% (between 70-90% is normal) .

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Table 5.1. Abbreviations used in pulmonary function testing. Abbrev.Term Definition IRV Inspiratory reserve volume The volume of air that can be inspired AFTER a passive inspiration TV Tidal volume The volume of air moved with each passive breath ERV Expiratory reserve volume The volume of air that can be expired AFTER a passive expiration RV Residual volume The volume of air in lung after maximal expiration TLC Total lung capacity The volume of air in lungs after maximal inspiration VC Vital capacity The difference in volume of air in lungs between a maximal inspiration and maximal expiration IC Inspiratory capacity The volume of air that can be inspired after a passive expiration FRC Functional residual capacity The volume of air in lungs after passive expiration. FVC Forced vital capacity The volume of air you can forcefully expire after a maximal inspiration FEV 1 Forced expiratory volume in 1 s The volume of air you can forcefully expire in the first second after a maximal inspiration PEF Peak expiratory flow The highest flow rate measured during expiration Obstructive lung diseases (FEV 1 /FVC below 70%) are groups of lung diseases that cause the patient to have difficulty exhaling at a normal rate, whereas, restrictive lung disease (FEV 1 /FVC above 90%) are groups of lung diseases that the patients have difficulty maximally inhaling ( i.e., fully expanding their lungs ). Both types of lung diseases share the same diagnostic symptom - shortness of breath on exertion . However, people with obstructive lung disease have shortness of breath due to difficulty exhaling all the air from their lungs, whereas, people with restrictive lung disease cannot fully fill their lungs with air. The most common causes of obstructive lung disease are chronic obstructive pulmonary disease (COPD; consists of emphysema and chronic bronchitis) and asthma. The most common causes of restrictive lung disease are stiffness of the chest wall, decreased compliance of the lung ( e.g. , pulmonary fibrosis), weak respiratory muscles or damaged respiratory nerves may cause the restriction in lung expansion. Obesity is another cause of restrictive lung disease.

Forced vital capacity . Have the subject do five forced vital capacity maneuvers using the digital handheld spirometer ( see image to the left ). Record their data in the table below. Select and circle their best trial as the trial with the highest peak expiratory flow (PEF) . Subject: Mohammad Hamideh Age: 20 Height: 1.75 m Mass: 75.75 kg Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Pred* % dif** FVC (L) 3.47 3.96 3.37 4.58 3.94 5.08 9.84 FEV 1 (L) 1.26 2.24 2.88 3.48 3.32 4.38 20.54 FEV 1 / FVC (%) .36 0.57 0.85 0.8 0.84 .86 1.2 PEF (L/s) 4.3 2.5 3.99 6.07 6.56 9.12 28 * Calculated and reported by the digital spirometer. This will be the same for all trials. ** % dif = [(Best - Pred)/Pred] x 100%

Post-lab questions for LAB 5 1. Make a graph ( XY scatter plot with straight lines connecting the dots ) of RPP vs . time for aerobic exercise. Make a caption and put it below your figure. Include pertinent information such as the mode of the exercises in the caption. 2. Print the rhythm strip from the ECG you recorded in class. Directly on the rhythm strip: a. Label the P wave, QRS complex, and T wave for one heartbeat b. Does the HR appear regular or irregular? What is the rate? Explain how you answered these questions. c. Label the PR interval and QRS complex and report their durations in seconds. Are they in the normal range? d. Label the ST segment. Is it normal, elevated or depressed relative to the baseline? 3. Report in a table the best trial, reference values, and % difference for FVC, FEV 1 , FEV 1 /FVC and PEF recorded with the digital spirometer for your subject. Make a caption noting subject demographic information and put it above the table. Post-discussion questions for LAB 5 4. Why are swimming, running, cycling, rowing called cardio exercises? Explain rate- pressure product and how it changes during dynamic, whole-body exercise. Refer to the graph in question 1 in your answer. 5. Print the 6 frontal leads (I, II, III, aVR, aVL, aVF): a. Put a rectangular box around the lead with the most isoelectric QRS complex b. Draw an arrow from the isoelectric lead to its perpendicular lead c. Put a circle around the lead perpendicular to the lead with the most isoelectric QRS complex d. Report the QRS axis in degrees e. Classify the QRS axis as normal, right-axis deviated or left-axis deviated 6. Does the subject you measured with the digital spirometer appear to have obstructive or restrictive lung disease? Refer the table from question 3 in your answer. 7. How would you expect FVC, FEV 1 , FEV 1 /FVC and PEF to change for individuals with obstructive and restrictive lung disease? Explain how ALL variables would change for each classification of lung disease.

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