Hemodynamics and BP Flashcards
What is the equation for cardiac output?
CO = HR x SV
What is the typical volume of blood contained in the vena cavae?
64%
What is the approximately cross-sectional area of the capillary system?
2500 cm^2
What is the site of highest resistance in the CVS?
Arterioles
What are the equations for flow?
F = V x A
F = V x r^2
F = deltaP/R
What is the definition of flow?
Volume of liquid or gas that is moving per unit of time
Why is peak velocity method not a good way to estimate flow?
It overestimates
Why is mean velocity method not a good way to estimate flow?
It underestimates
What is the most accurate way to determine flow?
Time-domain correlation method using doppler
Where is blood velocity the highest?
Aorta
Where is blood velocity the lowest?
Capillaries
What is the relationship between velocity and radius?
Inversely proportional
V = 1/r^2
What is the relationship between flow and resistance?
Inversely proportional
What is the equation for resistance?
R = deltaP/F
What are the general values of total peripheral resistance in systemic and pulmonary circulations?
Systemic - 1 peripheral resistance unit
Pulmonary - 0.14 PRU or 1/7 of systemic
What is the equation for conductance?
C = 1/R = F/deltaP
What is the definition of conductance?
Blood flow through a vessel for a given pressure difference
What is the relationship between temperature and velocity?
Inversely proportionate
What is Poiseuille’s equation for resistance?
R = (8 x eta x L)/(pi x r^4)
eta = viscosity
What is the equation for distensibility?
C = deltaV/deltaP
What is another name for capacitance?
Compliance
What can be the result of AV fistula in a major artery on resistance?
Decrease in peripheral resistance
What are the factors affecting vascular resistance?
Size of vessels
Organization of vascular network
Physical characteristics of blood
Extravascular mechanical forces
What is the affect of histamine and bradykinin on blood flow?
Arteriolar dilation and venoconstriction increase blood flow to the site of secretion
What is the affect of serotonin on blood flow?
Arteriolar constriction
What is the effect of thromboxane A2 on blood flow?
Vasoconstrictor
What is the effect of prostacyclin on blood flow?
Vasodilator
What is Reynold’s number used to predict?
Type of blood flow
If <2000 always laminar
Between 2000-3000 increased likelihood of turbulent
>3000 always turbulent
What increases Reynold’s number?
Increased velocity
Decreased viscosity –> anemia or decreased plasma proteins
Increased density
What is the equation for BP?
BP = CO x TPR
What is the relationship between systolic BP and CO?
Directly proportional
What is the relationship between systolic BP and arterial compliance?
Inversely proportional
What is the main determining factor in diastolic BP?
TPR
What is the equation pulse pressure?
PP = SBP - DBP
What is the normal range for pulse pressure?
20-50 mmHg
What are the most important determining factors pulse pressure and their relationship?
SV - directly proportional
Arterial compliance - inversely proportional
What factors can increase pulse pressure?
Aortic regurgitation
Hyperthyroidism
Arteriosclerosis
OSA
Exercise
What factors can decrease pulse pressure?
Aortic stenosis
Cardiogenic shock
Cardiac tamponade
Advanced HF
Hypovolemic shock
What is the equation for mean arterial pressure?
MAP = 2/3 DBP + 1/3 SBP
What is the equation for SVR?
SVR = (MAP - RAP)/CO
What is the equation for velocity?
V = P/R x A
What is the normal range for MAP?
75 - 105 mmHg
Why does the pressure decrease in arterioles?
Decreased velocity and increased resistance
How does gravity effect pressure below the level of the heart?
An increase by 0.77 mmHg per cm
How does gravity effect pressure above the level of the heart?
A decrease of 0.77 mmHg per cm
