HAP Practical: How to Measure Blood Pressure (BP)?

Aim: To learn how to use a Sphygmomanometer and Stethoscope to measure blood pressure.

Reference: 

Smith, J. K., & Johnson, L. M. (2020). Cardiovascular Physiology: Principles and Practice. Medical Publishers Inc. (pp. 120-135).

Required Materials:

• Sphygmomanometer
• Stethoscope
• Blood pressure cuff
• Pen and paper for recording measurements

Theory:

Blood pressure is an important physiological parameter. Blood pressure refers to the force exerted by circulating blood against the walls of blood vessels, primarily arteries, as it is pumped by the heart around the body. Monitoring blood pressure is crucial for assessing cardiovascular health and diagnosing conditions such as hypertension.
It is typically expressed in millimeters of mercury (mmHg) and consists of two main components: systolic pressure and diastolic pressure.

Systolic Pressure: This is the higher number in a blood pressure reading and represents the pressure exerted against arterial walls during the contraction of the heart (systole). It reflects the maximum pressure reached in the arteries when the heart contracts and pushes blood out into the circulation.

Diastolic Pressure: This is the lower number in a blood pressure reading and represents the pressure in the arteries when the heart is at rest between contractions (diastole). It reflects the minimum pressure in the arteries when the heart relaxes and refills with blood.

Regulation of Blood Pressure:

Blood pressure is regulated by a complex interplay of various physiological mechanisms, including:

1. Cardiac Output: The volume of blood pumped by the heart per minute (cardiac output) and the force of each heartbeat (stroke volume) influence blood pressure. An increase in cardiac output or stroke volume typically leads to higher blood pressure.
2. Peripheral Resistance: Peripheral resistance refers to the resistance encountered by blood flow in the systemic circulation, primarily determined by the diameter of blood vessels and their elasticity. Narrowing of blood vessels increases resistance, resulting in higher blood pressure, while dilation of blood vessels decreases resistance, leading to lower blood pressure.
3. Blood Volume: The total volume of blood in the circulatory system affects blood pressure. An increase in blood volume, such as through fluid retention or excessive intake of fluids, tends to elevate blood pressure, while a decrease in blood volume leads to lower blood pressure.
4. Hormonal Regulation: Hormones such as adrenaline, aldosterone, and antidiuretic hormone (ADH) play crucial roles in regulating blood pressure. For example, adrenaline (epinephrine) released during stress or excitement can temporarily raise blood pressure by increasing heart rate and constricting blood vessels.
5. Autonomic Nervous System: The sympathetic and parasympathetic divisions of the autonomic nervous system exert opposing effects on blood pressure regulation. Sympathetic activation typically increases blood pressure through mechanisms such as vasoconstriction and increased heart rate, while parasympathetic activation tends to decrease blood pressure by promoting relaxation and vasodilation.

Clinical Significance:

Monitoring blood pressure is essential for assessing cardiovascular health and diagnosing conditions such as hypertension (high blood pressure) and hypotension (low blood pressure). Hypertension, if left untreated, can lead to serious complications such as heart disease, stroke, and kidney damage. Therefore, maintaining optimal blood pressure levels through lifestyle modifications and, if necessary, medical intervention is crucial for overall health and well-being.

Procedure

Preparation:

• Ensure the participant is seated comfortably with their back supported and feet flat on the floor.
• Rest the participant’s arm on a flat surface, palm facing upward, and position it at heart level.
• Allow the participant to relax for 5 minutes before starting the measurement.

Applying the Blood Pressure Cuff:

• Select the appropriate cuff size based on the participant’s arm circumference.
• Wrap the cuff snugly around the upper arm, ensuring the bottom edge of the cuff is about 1 inch above the elbow.
• The artery marker on the cuff should be positioned over the brachial artery.

Palpating the Radial Pulse:

• Using your fingers, locate the participant’s radial pulse on the same arm as the cuff.
• Inflate the cuff by closing the valve on the bulb and squeezing it until the pressure gauge reads about 30 mmHg above the point at which the radial pulse disappears.

Measuring Blood Pressure:

• Place the diaphragm of the stethoscope over the brachial artery marker on the cuff.
• Slowly deflate the cuff by opening the valve on the bulb at a rate of 2-3 mmHg per second while listening for the first Korotkoff sound (the tapping sound).
• Note the pressure reading on the manometer when you first hear the tapping sound; this is the systolic blood pressure.
• Continue to deflate the cuff and listen for the disappearance of the tapping sound; note the pressure reading when the sound disappears completely; this is the diastolic blood pressure.
• Record the systolic and diastolic blood pressure readings.

Repeat Measurements:

• Allow a 1-2 minute rest period between successive measurements.
• Repeat the measurement at least twice, preferably on both arms, and calculate the average of the readings.

Documentation:

• Record all measurements accurately, including the arm used for measurement, position of the participant, and any relevant observations.
• Safety Precautions
• Ensure the cuff is not applied too tightly, as this can cause discomfort or obstruct blood flow.
• Do not inflate the cuff excessively, as this can cause injury or discomfort to the participant.
• If the participant experiences any discomfort during the measurement, stop the procedure immediately.

Discussion Questions

1. Why is it important to measure blood pressure accurately?
2. What factors can influence blood pressure readings?
3. How does hypertension affect cardiovascular health?
4. How can lifestyle changes help manage hypertension?
5. What are some potential sources of error in blood pressure measurement, and how can they be minimized?

Conclusion

Monitoring blood pressure is a fundamental aspect of assessing cardiovascular health. By accurately measuring blood pressure and understanding its significance, healthcare professionals can diagnose and manage various cardiovascular conditions effectively. Through this lab, you have gained valuable experience in blood pressure measurement techniques, which will be beneficial in clinical practice.