Blood Pressure Key Concepts and Measurement Techniques

Blood Pressure Overview

• Blood pressure (BP) refers to the pressure of circulating blood on the walls of blood vessels.
• Blood flow is initiated and regulated by the rhythmic contractions of the heart, which leads to a pulsating nature of blood pressure.
• BP varies between two key phases of the cardiac cycle:
• Diastole: The relaxation phase of the ventricles where a minimum blood pressure is recorded.
• Systole: The contraction phase of the ventricles where a maximum blood pressure is recorded.

Blood Pressure Measurement

• BP is commonly measured in millimeters of mercury (mmHg).
• Normal ranges:
• Diastolic Blood Pressure (DBP): 60-89 mmHg
• Systolic Blood Pressure (SBP): 100-139 mmHg
• Table 7.1 illustrates categories of blood pressure:

Variability in Blood Pressure

• BP can fluctuate significantly in short time frames, with changes of up to 30 mmHg observed within a minute.
• Mean Arterial Pressure (MAP) calculation:
• MAP = \frac{SBP + 2 \cdot DBP}{3}
• Pulse Pressure: The difference between systolic and diastolic pressures, useful for assessing BP status.
• Multiple readings are necessary for accurate BP assessment due to the variability of measurements.

Methods of Measuring Blood Pressure

• Blood pressure is typically measured using a sphygmomanometer and stethoscope:
• An inflatable cuff is placed on the upper arm and inflated.
• Once the cuff pressure exceeds SBP, it collapses the artery.
• As pressure is released, blood flow resumes, producing sounds known as Korotkoff sounds:
  • First Sound: Represents SBP; marking the point where blood flow just begins.
  • Second Sound: Represents DBP; marked by the sound's muffling or disappearance.

Automated Devices

• Modern automated devices have simplified this process, allowing for easy readings.
• They may utilize auscultatory or oscillometric methods to determine BP.
• Wrist devices are more convenient but less reliable compared to traditional methods.

Cardiovascular Reactivity

• Individual differences in cardiovascular responses can affect health outcomes; high levels of reactivity are linked to greater risk of cardiovascular diseases.
• Patients often do not recognize when they have elevated BP due to inaccurate assessments based on feelings rather than accurate readings.

Clinical Application

• Understanding BP measurement is crucial for both personal health monitoring and clinical practices.
• Goal of the Class: To learn BP recording techniques and understand the sounds of Korotkoff and automated device measurements.
• Using accurate, reliable methods is essential to avoid mismanagement of hypertension, particularly in self-treatment scenarios where patients might adjust medication based on inaccurate perceptions of their BP.