Arterial Blood Pressure Flashcards
What is blood pressure?
Force exerted by the blood against the walls of the blood vessels
What is arterial pressure?
Pressure exerted by blood on the arterial walls
What is venous pressure?
Pressure exerted by blood in the veins
Blood flows from _ to _ pressure
high to low
Average of capillary blood pressure
25 mmHg
Pulmonary pressure
Pressure in pulmonary circulation
8-20 mmHg
What is systolic pressure?
Pressure generated during ventricular contraction
Relation between SBP and cardiac output
Directly proportional
What is diastolic pressure?
Pressure during cardiac relaxation
Relation between DBP and total peripheral resistance?
Directly proportional
What is the average range of blood pressure
Lower normal: 90/60 mmHg
Average: 120/80 mmHg
Upper normal: 140/90 mmHg
Hypertension
More than 140/90 mmHg
Must be for two or more days for a hypertension diagnosis
Hypotension
Less than 90/60 mmHg
How is pulse pressure calculated?
Systolic BP - Diastolic BP
What tool is used in measuring BP?
Sphygmomanometer
What is Mean Arterial Pressure and how is it calculated?
Average of arterial pressures for one cardiac cycle
MAP = Diastolic +1/3 pulse pressure
Normal range of MAP?
70 to 100 mmHg
What are the functions of arterial blood pressure?
Maintains tissue perfusion
Produces capillary hydrostatic pressure which determines the filtration pressure affecting tissue fluid formation
Diastolic blood pressure:
Maintain blood flow during diastole
Essential for normal coronary blood flow
Prevent blood stasis in the arteries
What physiological factors influence ABP?
Age: BP increases with age
Sex: Higher in males
Body build: Higher in obese people
Diurnal variation: Lowest during sleep due to decreased sympathetic tone and highest after waking up
Exercise and emotions: Increase arterial blood pressure
Temperature: Low temperature = vasoconstriction and increase ABP
Respiratory movement
Gravity
How does age affect arterial blood pressure?
Birth: 70/50 mmHg
At 20: 120/80 mmHg
At 60: 140/90 mmHg
How does respiratory movement affect arterial blood pressure?
ABP shows rhythmic fluctuations during respiration called Trabue-Hering waves
ABP increases during late inspiration
ABP decreases during late expiration
What factors maintain ABP?
Cardiac output
Total peripheral resistance
Elasticity of the aorta (compliance)
Blood volume
How can arterial blood pressure be calculated?
Cardiac output x Resistance
How can cardiac output be calculated?
Stroke volume x Heart rate
Why is TPR important for ABP?
Helps maintain DBP
Where is TPR produced?
Arteriole
What factors determine the TPR?
Diameter of the vessel (Inversely proportionate to TPR)
Blood viscosity (directedly proportionate).
The length of the vessel (directedly proportionate).
How does atherosclerosis affect compliance?
Makes arterial walls rigid
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Average volume of blood?
4.7-5.5L
How do changes in blood volume affect ABP?
Increase blood volume → increase systemic filling pressure (Psf) → increase ABP
Low blood volume as in haemorrhage → low blood pressure (hypotension)
Systemic filling pressure (Psf) is the pressure in the systemic circulation when the blood flow is zero
It is = 7 mmHg
