Lab 5 - Cardio ECG and PFT

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California State University, Los Angeles *

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Mechanical Engineering

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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.

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°

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