Blood Pressure Flashcards
Mean blood pressure =
(systolic blood pressure +(2x diastolic blood pressure))/3
blood pressure basics
What type of flow in the aorta and large arteries?
pulsatile
What type of flow in the capillaries and veins?
laminar
If systemic arterial blood pressure is too low:
- faint (vaso-vagal attack)
- shock leading to tissue acidosis (pH<7.35)
If systemic arterial blood pressure is too high, leads to tissue damage
too high
Systemic arterial blood pressure is regulated to maintain
adequate tissue perfusion
Humans ideal blood pressure
120/80 mmHg
State the determinants of blood pressure:
- cardiac output
- vascular resistance
State the determinants of blood pressure: Cardiac Output:
- amount of blood pumped by the heart: c. 5L/min
- under hormonal and neurological control
State the determinants of blood pressure: Vascular Resistance:
- predominantly determined by the level of constriction of arterioles
- under hormonal and neurological control
Blood pressure Equation:
cardiac output x stroke volume
Ohm’s Law
V=IR
State 3 physical factors that affect blood pressure:
- gravity
- arterial compliance
- blood viscosity
Physical factors that affect blood pressure: Gravity:
- blood pressure is higher in feet, lower in head when standing upright….
Physical factors that affect blood pressure: arterial compliance:
- arteries stretch and store elastic potential energy in systole
- release energy to maintain flow in diastole
- stiff arteries (eg old age) reduces
compliance and increases systolic blood
pressure
Physical factors that affect blood pressure: blood viscosity:
- contributes to resistance to flow
- high protein/hypercellular blood has high
viscosity - higher pressure to maintain flow
Factors affecting CO and SVR
Cardiac output equation
CO = HR x SV
heart rate is per min
stroke volume is Liters
Usual cardiac output is
c.5L/min
Starling’s Law
- the mechanical energy set free in the
passage from the resting to the active state
is a function of the length of the fiber - fiber length is determined by end diastolic
volume (determined by venous return) - force contraction is translated into stroke
volume
Cardiac pressure volume
Preload is
venous return