Blood Pressure Lab Write-up Part I: Due 5PM Friday April 3 For Part I (which does not require you to complete the lab or use any data) produce the introduction and methods sections for a lab report for the how changes in body position affects blood pressure (see the lab manual posted on Canvas). Your report will only focus on the activity looking at the effect of body on blood pressure, not the entire lab activity. I am providing you an outline, but your report should be in nonnumeric, paragraph form. Next week, you will produce and submit the entire lab report, but do not worry about that right now. I will post the lab data you will use to complete the entire lab report Friday evening. The entire lab report will be due next week. 1. Write an Introduction Section (3-4 paragraphs). A brief overview of blood pressure should be included in this section. Make sure to include brief explanations of the physiology underlying the measurement of blood pressure and how to interpret the blood pressure reading. Make sure your reader can define key terms and understand key concepts. State the purpose of the activity. 2. Methods. Write 2-3 paragraphs which give an overview of how you did your experiment. Write a paragraph explaining the establishment of baseline blood pressure and heart rates. Write a paragraph which gives a general overview of how you used the methods and baseline data to study the effects of changes in body position on blood pressure and heart rate. EXERCISE 8: Blood Pressure Purpose: Blood pressure assessment (sphygmomanometry) is one of the most common physical tests performed in modern medical practice. This non-invasive procedure allows a health care professional to help determine the cardiovascular health of a patient by comparing recorded data against normal limits for a person’s age and sex. Today you will learn about the basic principles of sphygmomanometry and perform the procedure on your classmates. Introduction: Proper perfusion of vital organs is necessary for survival. The systemic arterial vessels must deliver blood to the peripheral capillaries in an efficient manner in order to meet the metabolic demands of the peripheral tissues. As the heart completes the ejection phase of ventricular systole the volume of blood ejected (the stroke volume) must be transmitted from the aorta to smaller arteries until this blood eventually reaches the capillary beds for gas exchange. This blood flow is directly proportional to the change in pressure along the vessel, and indirectly proportional to the resistance along the vessel. Resistance is determined by factors that would impeded or slow down blood flow. Blood viscosity, or thickness, and blood vessel diameter based on vasoconstriction and vasodilation are the key factors that determine resistance. The equation that expresses this relationship is F = ΔP. R Resistance is directly proportional to the viscosity of blood- therefore thicker blood will cause blood flow to decrease due to increased resistance. Resistance is indirectly proportional to the radius of the blood vessel raised to the fourth power (r4). Vasoconstriction, which decreases the vessel diameter, will increase resistance greatly and slow blood flow. Conversely, vasodilation, which increases the blood vessel diameter, will decrease resistance greatly and speed blood flow. The interplay between pressure changes and resistance determines the amount of stress a vessel wall is subjected to and the amount of work the left ventricle must due to open the aortic valve against aortic pressure. Blood pressure measurements are built on three physiologic principles: the cardiac cycle, aortic rebound, and elasticity of major blood vessels. Blood pressure is determined by applying pressure to the brachial artery and auscultating (listening to) the sounds of blood flow through the vessel. The sounds assessed through a stethoscope are called Korotkoff sounds and are based on how the blood is flowing through the compressed brachial artery. As pressure is applied to the brachial artery the blood flow through the vessel will be completely occluded, or blocked. As the pressure is slowly released from the sphygmomanometer the blood will slowly start to pass through the vessel, but it will be turbulent and make a lot of noise in the stethoscope. This first Korotkoff sound is the first “loud knock” heard in the stethoscope and is when the health care professional reads systolic pressure. Pressure is continually released from the cuff and blood flow will become “smoother” through the vessel because it is not squeezing through a small space. The blood flow sound will be more muffled (this is the second Korotkoff sound). When the blood finally flows smoothly through vessel the cuff is approximately equal to diastolic blood pressure. Most professionals read the diastolic pressure when the blood flow sounds disappear. (There are some variations in how health care professionals read diastolic pressure- some read at the last sound, others read at silence. This distinction makes a very small difference -a few mmHg- in diastolic pressure readings. As beginners, you will be reading at “silence” to make the procedure easier.) 60 The two values obtained directly from this process are the systolic and diastolic blood pressures. The systolic blood pressure reflects the pressure in the major arteries as blood moves through the vessel due to the contraction of the left ventricle. The diastolic pressure reflects the pressure in the major arteries while the left ventricle is relaxed. When these values are recorded in a file they are written with the systolic pressure in mmHg over the diastolic pressure in mmHg: systolic. diastolic Additional values can be calculated from the systolic and diastolic pressures that are also used to assess patient health are the pulse pressure and mean arterial pressure (MAP). The MAP must be high enough to supply tissues with sufficient oxygen, but a very high MAP may be indicative of cardiovascular stress and/or disease. The pulse pressure is calculated by subtracting the diastolic pressure from the systolic pressure (systolic-diastolic). (This number should be positive. If you calculate a negative pulse pressure check your original recordings and ensure that you have set up the equation properly). The MAP requires that you calculate the pulse pressure first. To calculate the MAP add the diastolic blood pressure to 1/3 of the pulse pressure: MAP = pulse pressure + diastolic blood pressure 3 The pulse pressure can help a physician determine the relative stroke volume (blood ejected by the left ventricle) and the resistance in the arteries. The MAP helps determine the average rate of blood flow in the systemic arterial circuit as well as the relative stress the blood vessels are heart are subjected to. The MAP must be a minimum of 60mmHg to keep organs properly perfused, and normally ranges from 70-110mmHg. High MAPs indicate that the cardiovascular system is stressed and may not function normally. The following table shows current AHA (American Heart Association) guidelines. Classification Normal/Healthy Systolic Diastolic 110 Prehypertension Stage 1 Hypertension Stage 2 Hypertension Hypertensive Crisis Materials Needed: 1. Automatic sphygmomanometer 2. Stethoscope 3. Yoga mat or towel 61 Experimental Methods: 1. Attach the blood pressure cuff to the left arm of your volunteer. 2. Press start on the cuff to read blood pressure and heart rate of the volunteer. 3. Read the blood pressure and heart rate twice, then average the values. Be sure to average the systolic and diastolic pressures separately! 4. Repeat steps 1-3 with the right arm. 5. Have the volunteer lay down and stay quiet for 3 minutes. 6. Attached the blood pressure cuff to the right arm of your volunteer. 7. Press start on the cuff to read blood pressure and heart rate of the volunteer. 8. Read the blood pressure and heart rate twice, then average the values 9. Repeat steps 6-8 on the left arm. 10. Have the patient exercise for 3-5 minutes, or until heart rate is significantly raised 25-50% above seated heart rate). 11. Once exercise is stopped, record blood pressure and heart rate from left arm twice and average the data. 12. Repeat readings five minutes after exercise has stopped. 13. After your data is gathered, calculate the pulse pressure and mean arterial pressures of the data. 62 Data Analysis: Blood Pressure Subject Name: ___________________________ Condition Left arm (seated) Trial Average Age:___________________ Heart Rate 1 2 Right arm (seated) 1 2 Right arm (laying down) 1 2 Left arm (laying down) 1 2 Post Exercise (Immediate) 1 2 Post Exercise (5 minutes) 1 2 63 Average M / F Table 2: Calculations (mmHg)- calculate off the averages from Table 1 Condition Left arm (seated) Right arm (seated) Right arm (laying down) Left arm (laying down) Left arm (post exercise) Left arm (5 minutes after exercise) Pulse Pressure MAP 64 PART II. CARDIOVASCULAR RESPONSES TO VARYING RESPIRATORY ACTIVITIES The cardiovascular system is extremely sensitive to the pressure changes in the thoracic cavity due to respiratory movements. Lower intrathoracic pressures can elicit stronger heart contraction. In addition, respiratory movements can also stimulate venous return to the heart, which serves to enhance stroke volume. The result is increased cardiac output, which then results in increased arterial blood pressure. Often, this elicits a carotid sinus or aortic reflex that results in a slowing of the heart. The opposite, elevated intrathoracic pressures may elicit other reflexes. The effects of some respiratory movements will be demonstrated in the present exercise. A. Basic Procedure 1. Use the automatic sphygmomanometer for this part of the exercise. 2. The subject’s heart rate and blood pressure should be monitored before, during and for 5 minutes after both of the following maneuvers. Use the same subject for each procedure. B. VALSALVA MANEUVER: Read all instructions for this maneuver before proceeding. 1. The subject will be seated and have two minutes of rest while heart rate is monitored and blood pressure is taken once every 30 seconds. The subject should try to limit extraneous movement. 2. The subject should then take a long, slow, deep inspiration, followed by strong forced expiration against a closed glottis (as in the strain of defecation), creating a positive intrathoracic pressure. Hold as long as possible. (This is the Valsalva Maneuver) a) During the maneuver, take pulse and pressure twice. b) Observe the subject’s color and make a note of it in the table on the next page. 3. Allow five minutes of rest while you continue recording the heart rate and blood pressure. a) Check heart rate and blood pressure. You will need these data for each 30 second period for five minutes. Continue to observe the subject’s color and make a note of it in the table. 65 b) Calculate MAP for each event, using the data from your BP readings, using: (MAP = Diastolic Pressure + 1/3 pulse pressure, where Pulse pressure = Systolic Pressure – Diastolic Pressure) Table 1: VALSALVA M ANEUVER Event Heart Rate (bpm) Blood Pressure (mm Hg) Calculated Pulse Pressure (mm Hg) Rest: Time 0 Time 0.5 min Time 1.0 min Time 1.5 min Time 2.0 min Valsalva Reading 1 Valsalva Reading 2 Rest: Time 0 Time 0.5 min Time 1.0 min Time 1.5 min Time 2.0 min Time 2.5 min Time 3.0 min Time 3.5 min Time 4.0 min Time 4.5 min Time 5.0 min 66 Calculated Mean Arterial Pressure (MAP) Subject’s Color C. MUELLER MANEUVER Following the rest period after the Valsalva Maneuver, the subject should then take a long, slow expiration, followed by a strong forced inspiration against a closed glottis, creating negative intrathoracic pressure (the sensation of breathing in against resistance). This is the Mueller Maneuver. Hold as long as possible. Record heart rate and blood pressure as you did in the previous maneuver. Calculate MAP. Enter your data into the table below. Continue taking readings for 5 minutes as the subject rests. Table 2: M UELLER M ANEUVER Event Heart Rate (bpm) Blood Pressure (mm Hg) Calculated Pulse Pressure (mm Hg) Mueller Reading 1 Mueller Reading 2 Rest: Time 0 Time 0.5 min Time 1.0 min Time 1.5 min Time 2.0 min Time 2.5 min Time 3.0 min Time 3.5 min Time 4.0 min Time 4.5 min Time 5.0 min 67 Calculated Mean Arterial Pressure (MAP) Subject’s Color Lab Summary and Review Questions Use your notes, data, and physiology textbook to answer these questions. DEFINITIONS: perfusion: pulse pressure: (total) peripheral resistance: mean arterial pressure: 1. Why is blood pressure traditionally read from the left arm rather than the right arm? Be sure to explain the anatomy and physiology of the blood flow to the brachial arteries. 2. Does your systolic and/or diastolic pressure change as your heart rate increases? If they do, which pressure changes the most? Can you explain the changes? 3. How do these changes affect the pulse pressure and MAP? Physiologically, why do these changes occur? 4. Why aren’t we reading systemic venous pressure? 68 5. Did your volunteer’s heart rate and blood pressure return to normal 5 minutes after exercise? If not, could you explain why? 6. Why is the MAP NOT equal to only (systolic pressure-diastolic pressure)? 2 7. Explain why the presence of atherosclerotic plaques along peripheral vessels may increase pressure in the systemic arterial system. 69 
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