Understanding Blood Pressure and Cardiac Output

Blood Pressure (BP)

• BP is the pressure exerted against vessel walls by blood
• Determined by cardiac output (CO) and vascular resistance
• Measured as systolic (maximum) over diastolic (minimum) pressure
• Typically reported in mmHg
• Normal resting BP is <120/<80 mmHg
• Recent changes to hypertension classifications: ≥130/80 mmHg

Cardiac Output (CO)

• CO = Heart Rate (HR) × Stroke Volume (SV)
• HR is the number of heart beats per minute
• SV is the amount of blood pumped per beat

Vascular Resistance

• Resistance exerted against blood flow
• Determined by vessel diameter; smaller diameter = greater resistance
• Exercise increases vascular resistance

Systolic Blood Pressure (SBP)

• Maximum pressure during ventricular contraction (systole)
• Usually higher than diastolic pressure

Diastolic Blood Pressure (DBP)

• Minimum pressure during ventricular relaxation (diastole)
• Usually lower than systolic pressure

Factors Affecting BP

• Body position (e.g., orthostatic hypotension)
• Hydration
• Stress
• Exercise
• Sex
• Age
• Muscle actions
• Disease

Measuring BP

• Indirect measurement using a sphygmomanometer and stethoscope
• Cuff size is critical to accuracy
• Clothing and environmental factors should be minimized
• Appropriate arm position and rest periods should be considered
• BP readings from both arms are initially compared
• Use the higher reading for assessment in a clinical setting

Hypertension

• Elevated BP readings considered hypertension
• Classifications have changed from ≥ 140/90 to ≥130/80 mmHg

Exercise Testing & BP

• BP can be an indicator of the heart's work
• BP measurement accuracy is vital in exercise physiology
• Preparation for BP measurements (e.g., avoiding stimulants, loose clothing)
• Measurements under standardized conditions are critical for accuracy in exercise settings