EE3810_Lab1_Morales

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M o r a l e s | 1 Lab 1: Blood Pressure and the Sympathetic Nervous System Amy Morales EE 3810-01 California State University, Los Angeles Dr. Won, Professor Diaz, Professor Giang Lab Conducted: January 31, 2024 Lab Due Date: February 7, 2024

M o r a l e s | 2 Objective The purpose of this laboratory exercise is to first introduce how blood pressure sensing works by taking a baseline record of our blood pressure. After doing so and familiarizing ourselves with the electronic sensor used by the arm cuff, we will observe how the body prepares itself for any changes (when in danger) that may occur to the body, through the representation of our blood pressure. To achieve this response from the body, we will be simulating a threat (or “fight or flight” response) by submerging our hand into an ice water bath to then immediately measure the changes in our blood pressure. By doing so, we will then be able to observe the changes in our blood circulation through the different blood pressure quantities that include the following: Systolic Pressure, Diastolic Pressure, Mean arterial pressure, and Pulse. Background/Theory The following information is adapted from the EE 3810 Lab Manual and other resources Blood Pressure Blood pressure is a measurement that represents the changing fluid pressure that is within the circulatory system. In other words, it is the force that your heart uses to pump blood around the body. Blood pressure is measured in millimeters of mercury (mm Hg) and given by the ratio of systolic pressure over diastolic pressure. The systolic pressure is a result of a peak pressure that is produced by the contraction of the left ventricle. While the diastolic pressure is the result of when the left ventricle is relaxing. In general, an ideal blood pressure is between 90/60 mm Hg and 120/80 mm Hg. Anything higher than that is considered to be high blood pressure and anything lower than is considered to be low blood pressure. High blood pressure is often a result of unhealthy lifestyle habits, such as being overweight and not exercising enough. If left untreated, the chances of developing long term health conditions, such as damaging the blood vessels in your kidneys, increases over time. Low blood pressure on the other hand, tends to be less common. This can arise from side effects caused by medication, or it could be caused by something far more serious like heart failure. When getting your blood pressure taken, you might notice a number in parentheses or besides the reading. This number is what is known as the mean arterial pressure (MAP) and it is crucial to doctors because this allows them asses the blood flow through your body (such as the brain, heart, and kidneys). It can be seen as the average pressure in your arteries throughout one cardiac cycle. A normal MAP tends to be between 70 mm Hg and 100 mm Hg. Anything higher than 100 mm Hg alerts doctors that there’s a lot of pressure in your arteries and that can lead to your heart muscle getting damaged due to how it has to work harder. On the other hand, anything under 60 mm Hg is considered to be a low MAP and that tells doctors that not enough blood is reaching your major organs, which could lead to them failing/dying. Sympathetic Nervous System

M o r a l e s | 3 The sympathetic nervous system is a network of nerves that helps our bodies activate what is know as the “fight or flight” response. The activity of this system increases whenever the body is under any stress or danger, or physically active. The effects of this lead to increased heart rate, increased breathing, sharp eyesight, and even a slowed down digestive system. In this lab exercise, the changes that occur to activate the sympathetic nervous system will be examined through a cold stimulation. Oscillo metric method of blood pressure measurement For this lab exercise, the blood pressure will be measured using what is known as the Oscillo metric method. It is solely based on the idea that arterials walls flex when the blood is pumped through the arteries by the heart. To acquire this measurement, the cuff is first wrapped around the arm (2cm above the elbow) to obstruct the brachial artery. When the cuff is inflated and then slowly deflated, this results in an arterial pressure pulse forming. Once the cuff is inflated to a point where the artery is completely obstructed, this stops the blood’s pulsations. As the pressure is slowly released from the cuff, the blood pressure will increase until a maximum “peak” is reached. Once that “peak” is reached, the pulses will begin to decrease due to how the cuff itself is becoming lose. Methods The following lab procedure is adapted from the EE 3810 Lab Manual Part 1: Baseline Blood Pressure 1. Connect the Blood Pressure Sensor (arm cuff) to the Vernier computer interface (Lab Quest). After doing so, connect the computer interface to a computer that has Logger Pro installed. 2. Attach the Blood Pressure cuff around the upper arm of the subject and about 2 cm above the elbow as show in Figure 2.1 3. Have the subject sit still in a chair with their forearm resting on the table throughout the start and end of the measurement recording. 4. Start to collect the data through Logger Pro and then immediately pump the cuff to at least 160 mm Hg (meter shown in Logger Pro). Stop pumping once you have reach at least 160mm Hg and watch as the meter goes down because once it has drop below 50 mm Hg you may stop recording the data. * 5. Record the data shown and store your data. *Note: Do not remove the cuff from the subject* Figure 2.1: Represents how to properly attach blood pressure cuff around your arm Part 2: Cold Stimulation Response Blood Pressure

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M o r a l e s | 4 1. Before beginning the second part of the lab exercise wait approximately 10 minutes. While waiting, one person from the group should start preparing the ice water bath for the subject. 2. Once the 10 minutes have passed, have the subject place their opposite hand (the one which the arm cuffed is not attached to) in the ice water bath for 15 seconds. 3. As soon as the subject’s hand enters the ice water bath, begin to collect the data and pumping the cuff to at least 160 mm Hg. (Once the meter has reached at least 160 mm Hg, you may stop pumping.) 4. After 15 seconds, the subject may remove their hand from the ice water bath and allow the blood pressure to drop to50 mm Hg (or lower) to then stop collecting the data. 5. Remove the arm cuff from the subject 6. Record the data shown and store your data. Data Analysis/Results Graphs below have been computed by Logger Pro Baseline Blood Pressure Graphs Figure 3.1- Graph shows the DC component and AC component of the baseline blood pressure recorded. The graph on the top corresponds to the DC component but only from the moment the cuff is not pumped anymore, which creates the blue decreasing line. The graph on the bottom corresponds to the AC component, which forms an oscillatory waveform. Both graphs are with respect to time (s). Cold Stimulation Response Blood Pressure Graphs (Figure 3.2)

M o r a l e s | 5 Figure 3.2- Graph shows the DC component and AC component of the cold stimulation response blood pressure recorded. The graph on the top corresponds to the DC component but only from the moment the cuff is not pumped anymore, which creates the blue decreasing line. The graph on the bottom corresponds to the AC component, which forms an oscillatory waveform. Both graphs are with respect to time (s). Blood Pressure Data Table 1 -- Blood Pressure Data Condition Systolic Pressure (mm Hg) Diastolic Pressure (mm Hg) Mean Arterial Pressure (mm Hg) Pulse (beats/minute) Baseline 136 mm Hg 57 mm Hg 81 mm Hg 79 BPM Cold Stimulus 119 mm Hg 68 mm Hg 88 mm Hg 124 BPM Table 1- Represents the Data taken from my lab partner, who was the subject for this lab exercise. The table shows the data for both the baseline blood pressure measurements and the cold stimulus blood pressure measurements. These recording were taken by the blood pressure cuff that was connected to the vernier computer interface. From there, the data was presented to me on Logger Pro. Question and Answers Following questions are from the 3810 Lab Manual 1. Think about how the blood pressure is measured in this lab. Watch the meter as the cuff pressure falls. Write your observations. What physiological events or behavior correspond to these observations? a. When first pumping the cuff, the pressure skyrocketed and continued to go up as I continued to pump the cuff. However, as soon as I let go and the pressure of the cuff started to go down, I noticed how the line of the blood pressure began to slowly decline. The DC component of the top graph doesn’t really show with much detail the Oscillo metric method, but I was able to somewhat tell when it was occurring by the shape of the line. If you look closely at the line, you can tell that around the middle, there are very small changes in direction and that is exactly where the oscillation of the blood flow started. After the data was stopped and I was paying much more attention, I realized that Logger Pro generated a close up of the oscillating waveforms which

M o r a l e s | 6 in fact is the AC component of my lab partner’s blood pressure. I observed how the AC component increased in amplitude, reached a peak, and then started to decrease in amplitude again until it just stopped generating the waveform. With what I had learned in the lectures, I was able to connect the points I had learned by visualizing it happen in real time. The waveform began to increase in amplitude slowly due to how that is when the blood starts flowing sufficiently, which goes back to the idea of the water hose. When the water hose at first is slowly let go of, the water starts to flow at a sufficient rate, but just like in the waveforms generated, there comes a time in which a peak is hit. That peak is hit around the middle and that is when more blood, or water in the case of the hose analogy, starts to flow. After hitting its peak, the amplitude of the waves started to decrease and that is when the cuff started to become more and more loose, reaching a point at which there was no more pressure to release. 2. Provide two graphs from the blood pressure measurements at baseline, showing A) the AC component and B) the DC component of the blood pressure measurement. Explain what each one shows and represents. a. The AC and DC components of the blood pressure measurements at baseline are shown in Figure 3.1. The AC component (bottom graph of Figure 3.1) represents the pulsed blood flow in the artery, which is created when the heart is contracting and relaxing. These waveforms similarly compare to Korotkoff sounds. The difference is that instead of sound waveforms, the Oscillo metric method uses the pressure pulses to form the waveforms. These are produced between the systolic (SBP) and diastolic blood pressures (DBP) because this is when the artery is collapsing completely and then reopening with each heartbeat. The first pressure pulse is the beginning of the waveforms being created, and this so happens to determine the systolic blood pressure as well. As more blood starts to flow and the cuff starts to slowly depressurize, the amplitude of the waveforms increases with respect to time. A peak is hit as more and more blood flow goes through the artery, which is when the pulses are the strongest. Once that peak is hit, the amplitude of the waveforms starts to decrease and that is due to how the cuff starts to become more and more loose with respect to time as well. When this occurs, the pulses get softer and then there comes a time in which all pulses cease, which is when the diastolic blood pressure is determined. As for the DC component (top graph of Figure 3.1), the graph represents the static blood flow in the artery, vein, and tissue. In the graph you are able to tell when the cuff is being pumped by the skyrocketing line in the beginning. Once it is let go off, the graph begins to decrease with respect to time and that decreasing line is the DC component due to how it keeps decreasing in the same direction. 3. Describe the trends that occurred in the systolic pressure, diastolic pressure, mean arterial pressure, and pulse with cold stimulus. How might these be useful in a “fight or flight” response? a. The diastolic pressure, mean arterial pressure, and pulse increased during the cold stimulus. The only thing that did not increase was the systolic pressure, but that might have been

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M o r a l e s | 7 caused due to how the cuff was pumped to over 200 mm Hg during the first part and not for the second part. The increase, however, on the other 3 recordings, show how much harder the heart had to work to pump the blood. Due to this, the pulse begins to quicken. While all this happens, the body as well gets in the “fight or flight” response that causes blood vessels to constrict and the body releases stress hormones, which as a result increases a person’s blood pressure. If the blood pressure increases, and the body reacts as explained, that would indicate that the other three measured quantities would increase as well. Conclusion All in all, it was found that the body’s “fight or flight” response causes an increases in the different blood pressure quantities: Systolic Pressure (not in my lab partner), Diastolic Pressure, Mean Arterial Pressure, and Pulse. The increase of my lab partner’s three out of the four blood pressure quantities shows how the sympathetic nervous system was affected by the cold stimulation by his increased heart rate. Science and data says that one should expect an increase on all four blood pressure quantities upon the introduction of the cold stimulus. However, the data collected showed that my lab partner’s systolic pressure dropped instead. Despite that only discrepancy, everything else had positive trends and correlated with the idea of how there would be an increase in the measured quantities. The discrepancy could have been caused by the different occasions in which we stopped pumping the cuff. For the baseline blood pressure, we pumped the cuff up to over 200 mm Hg and did not do the same for the cold stimulus reaction blood pressure. Another issue could have been that for the cold stimulus procedure, we repeated the procedure 3 times and stuck to the last set of recordings. It may even be that my lab partner was not entirely in a truly relaxed state when the recordings where taken. References

M o r a l e s | 8 [1] P. S. Lewis, “Oscillometric measurement of blood pressure: a simplified explanation. A technical note on behalf of the British and Irish Hypertension Society,” Journal of Human Hypertension , vol. 33, no. 5, pp. 349–351, May 2019, doi: https://doi.org/10.1038/s41371-019-0196-9 . [2] A. Chandrasekhar et al. , “Formulas to Explain Popular Oscillometric Blood Pressure Estimation Algorithms,” Frontiers in Physiology , vol. 10, Nov. 2019, doi: https://doi.org/10.3389/fphys.2019.01415 . [3] NHS, “What is blood pressure?,” NHS , Sep. 17, 2019. https://www.nhs.uk/common-health-questions/lifestyle/what-is-blood-pressure/ [4] D. DeMers and D. Wachs, “Physiology, Mean Arterial Pressure,” PubMed , 2020. https://pubmed.ncbi.nlm.nih.gov/30855814/ [5] “Mean Arterial Pressure: Normal, Low, High Readings Plus Treatment,” Healthline , Apr. 10, 2018. https://www.healthline.com/health/mean-arterial- pressure#treatment [6] Cleveland Clinic, “Sympathetic Nervous System (SNS),” Cleveland Clinic , Jun. 06, 2022. https://my.clevelandclinic.org/health/body/23262-sympathetic- nervous-system-sns-fight-or-flight