Blood Pressure Basics

Blood Pressure

• Defined as the pressure of blood in the arteries, a result of heart output and vascular resistance
• Consists of systolic pressure (pressure during heart contraction) and diastolic pressure (pressure when heart relaxes)
• Measured in millimeters of mercury (mmHg)
• Pulse pressure (PP) is calculated as: PP = Systolic Pressure (SP) - Diastolic Pressure (DP)

Normal, High, and Low Blood Pressure

• Normotension (normal blood pressure): 120/80 mmHg
• Hypertension (high blood pressure): >140/90 mmHg
• Hypotension (low blood pressure): <100/60 mmHg
• Optimal BP: <120/80 mmHg
• Normal high BP: 130-139/85-89 mmHg

Factors Affecting Blood Pressure

• Age: Blood pressure generally increases with age, starting lower in childhood
• Gender: Women tend to have lower blood pressure than men, but this changes after menopause
• Diurnal Rhythm: Blood pressure naturally fluctuates throughout the day, decreasing during sleep and increasing in the morning.
• Exercise: Temporarily increases blood pressure. Normal levels return after exertion.
• Emotions: Emotions can cause vasoconstriction and stimulate the sympathetic nervous system, which increases blood pressure. Severe pain might lower blood pressure.
• Fever: Blood pressure increases due to increased metabolism.
• Bleeding: Blood pressure typically decreases.
• Heat/Cold: Heat generally lowers blood pressure, while cold tends to increase it
• Obesity: Blood pressure may increase with obesity.

Lifestyle Factors Affecting Blood Pressure

• Smoking: Increases blood pressure, returning to baseline after 15 minutes
• Alcohol: Increases blood pressure through vasoconstriction
• Excessive sodium intake: Increases blood pressure

Medication

• Intravenous fluids can increase blood pressure
• Some medications lower blood pressure.

Diseases

• Various diseases can affect blood pressure

Blood Pressure Measurement Sites

• Brachial artery: Most common measurement site
• Popliteal artery: Used when brachial artery access is not possible
• Radial/Humeral artery: Used for measuring one-sided readings

BP Measurement Methods

• Direct (Invasive): Catheter with electronic sensor inserted in an artery
• Indirect (Non-invasive):
  • Palpation: Measuring only systolic pressure, used in emergency situations
  • Auscultation: Standard method using a stethoscope and sphygmomanometer to detect Korotkoff sounds
  • Oscillometric: Measures BP by detecting oscillations in artery walls using a digital device
  • Ultrasound: Measures systolic pressure when Korotkoff sounds are difficult to detect; uses Doppler effect

Blood Pressure Devices

• Aneroid sphygmomanometer: Manual measurement device that measures blood pressure
• Digital BP monitor: Automated devices with automatic or manual cuff inflation.
• Automated-auscultatory/hybrid sphygmomanometer: Combines auscultatory and oscillometric methods
• Portable Doppler ultrasound: For situations where Korotkoff sounds aren't easily heard