PAM2HP2 workshop 3_online

Cardiovascular (Blood Pressure) High blood pressure has no symptoms but is a major risk factor for heart attack and stroke Before Class: As part of your preparation for this workshop: 1. Review this week’s online content before coming to your workshop 2. Read this week’s workshop notes and bring a copy to your workshop 3. Watch the demonstration on the LMS on how to measure blood pressure 1 Week THREE Workshop Semester 2 / 2022 PAM2HP2 – Human Physiology 2 La Trobe University

Workshop Overview: The effect of posture on blood pressure: During this part of the workshop, you will be measuring the blood pressure of one (or more) of your group members. You will be using an automated blood pressure monitoring device for this prac and examining the effect of different postures on mean arterial pressure. Short answer questions: You will complete a number of short-answer questions based on the practical activity and this week’s content. You should work through these answers and discuss them with your peers/facilitator as you go. These questions are only for your own learning – they are not formally assessed but will give you valuable practice at answering the style of questions that you will encounter in your end-of-module assessments. After you have completed these questions, your tutors will discuss the answers with the class. Menti questions : In the last part of today’s workshop you will participate in a class menti session where we will use the polling program Mentimeter. The purpose of this MCQ session is to give you a feel for how well you understand this week’s content and is for your own feedback on your learning – it is not a formal assessment and does NOT contribute to your mark for the subject. 2 WARNING: if you have any medical condition which might influence your ability to perform any of the activities in this workshop, or put you or someone else at risk, DO NOT volunteer for those activities as a subject. It is your responsibility to assess your suitability, otherwise do not participate. If necessary, please make your facilitator aware of your condition.

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Experimental Protocol The auscultatory method Please watch the video on the LMS demonstrating the auscultatory method for measure blood pressure. You will not be performing this but you will use an automated device to measure blood pressure using the same technique. A description of the technique is given below. 1. It is conventional to reference all arterial blood pressure measurements to the position of the heart. Choose one subject and have them in a seated position with the elbow slightly flexed (as shown in Figure 1); the flexed elbow should be at the level of the heart. If the subject feels anxious, wait a few minutes before taking the pressure. Figure 1. Subject position when measuring blood pressure. 2. Remove any tight-fitting clothing from the upper left arm and wrap the cuff around the upper arm with the cuff’s lower edge ~2cm above the antecubital fossa. Lightly press the stethoscope's bell over the brachial artery just below the cuff's edge. 3. Rapidly inflate the cuff to 180mmHg. Release air from the cuff at a moderate rate (~3mmHg/sec). This will require some practice. If you find that the air is released too quickly, release all the air immediately, wait a few seconds and start again. DO NOT KEEP THE CUFF INFLATED FOR LONG PERIODS. 4. Listen with the stethoscope and simultaneously observe the sphygmomanometer. The first knocking sound (Korotkoff) is the subject's systolic pressure. When the knocking sound disappears, that is the diastolic pressure (such as 120/80mmHg). 5. Repeat the procedure on the same subject and record your results in Table 1 below. Table 1. Record your results for Part A here 5 Subject Systolic Pressure(mmHg) Diastolic Pressure (mmHg)

Individuals with high blood pressure are at a higher risk of haemorrhagic stroke. This is due to a number of factors, included the damage caused to the blood vessels by high bloody pressure so that they are weaker and blockages cause in your artery. Part B: Effects of posture on blood pressure Aims & Objectives At the end of this workshop, students should be able to: 1. describe the impact of various postures on blood pressure Supine position: Standing position: Due to gravity the blood pressure Sitting position: You will be able to achieve these aims by actively participating in the experimental procedures that follow. Safety considerations Blood pressure measurement is a standard clinical procedure and carries no risk if it is correctly carried out. The equipment used is built to clinical safety standards. The tissues supplied by the brachial artery (resting muscle, connective tissue, skin, fat, bone) are tolerant to brief periods of ischaemia (absence of blood flow) and are not injured during blood pressure measurements. However never leave the cuff inflated on the subject’s limb for extended periods of time (ie., over 30sec) . Background Details Gravity is a constant force that influences nearly every aspect of biological activity, to some extent. The gravitational force on organisms follows physical laws that are well-known; thus, the gravity can have predictable effects. Any fluid columns, like blood vessels, are subjected to large pressure 7

gradients when subjected to sudden changes in body posture, especially in humans which are designed for upright posture. There are physiological adaptations in the human cardiovascular system designed to counteract the effects of gravity on the circulatory system under postural changes such as when in a standing, sitting, or lying down (supine) position. Some of the things that occur in the body in response to changes in posture are heart rate and blood pressure. When you lie down in the supine position, your heart is at the same gravitational level as the blood vessels in our head and limbs. Therefore, when lying down your blood pressure is similar along your entire body and blood return to the heart is less influenced by the pull of gravity. However, when you stand for a long period of time without moving, or when you have laid down for a long time and stand up suddenly, you might experience a feeling of faintness or dizziness that passes quickly. This slight dizziness is due to the effects of gravity on the cardiovascular system. This sudden posture change from a supine to an upright posture creates a strong vertical gradient of gravitational pull on the fluid (blood) in our circulatory column. The heart is now below the head and neck, and the heart is approximately 1m above the legs. Blood pressure decreases briefly in the head and neck while pressure increases in the legs. Furthermore, the increased blood pressure in our lower limbs causes blood to pool in our venous system because the veins are thin and compliant, unlike the elastic- walled arterial vessels. The venous system stores about 80% of your total blood volume while the arterial system stores about 10% at any one time. Thus, the venous system is a blood reservoir. Experimental Protocol – the oscillometric technique 1. Choose one subject within your group to perform the following protocol. 2. Remove any tight-fitting clothing from the upper left arm and wrap the cuff around the upper arm with the cuff’s lower edge ~2cm above the antecubital fossa. Make sure the air tube runs down the inside of the subject’s arm and the air plug is securely inserted in the main unit as shown below. 3. With the subject in a seated position (arm resting on the table, press the START/STOP button. The cuff starts to inflate automatically. As the cuff inflates, the monitor automatically determines the subject’s inflation level. The monitor will also detect the pulse during inflation. DO NOT MOVE YOUR ARM AND REMAIN STILL UNTIL THE ENTIRE MEASUREMENT PROCESS IS COMPLETED. 8

Table 3. Additional data set for analysis Seated Supine Supine (arm raised) Supine (arm lowered) Standing Supine (ankle) Standing (ankle) Subject SP DP SP DP SP DP SP DP SP DP SP DP SP DP 1 128 82 132 75 115 58 135 79 130 80 127 79 215 158 2 135 79 134 82 105 60 142 81 136 82 130 80 218 168 3 112 78 118 77 102 61 120 79 115 76 115 77 205 151 4 122 75 125 80 105 62 139 79 120 78 118 79 204 158 5 129 83 132 85 114 60 135 85 125 80 128 81 218 171 6 124 82 120 84 108 59 132 83 129 79 124 79 210 165 7 134 80 138 78 110 57 142 81 129 82 135 77 220 177 8 139 79 130 83 113 61 147 80 132 83 130 80 214 162 9 128 81 122 78 109 60 135 83 125 84 130 82 209 165 10 Mean SD Calculate mean arterial pressure in each condition using the data from your participant and the data from table 3. Calculate the mean  SD of the SBP, DBP and MAP for each condition. The excel spreadsheet with this data is available on the LMS. Which condition had the highest arterial pressure? The highest arterial pressure was standing at the ankle. Discussion Questions 1. In which circumstance will the pressure in the brachial artery be the same as the pressure in the aorta? 2. Calculate the hydrostatic pressure (in mmHg) in the dorsalis pedis artery (in the foot) with the subject standing up. How would the blood pressure in the dorsalis pedis artery (in the foot) differ to the pressure in the brachial artery in a person (a) standing up and (b) in supine position? 3. What do you think will happen to heart rate after you stand up after lying down for 5 minutes. Give a biological explanation, based on what you know about cardiovascular physiology. 4. Why would a jet pilot or astronaut wear a tight suit when embarking on a flight? 10

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