Hemodynamics I

Front 1

1. What is the study of the physical factors that determine blood flow and blood pressure in the body
2. What are the physical factors from 1?
3. Goal of low velocity in capillaries?

Back 1

1. Hemodynamics
2. force, velocity, flow, resistance, diameter, and viscosity
3. Increase time for exchange of substances

Front 2

1. What is defined as the mass movement of a volume of fluid (blood) per unit time
2. expression of conservation of mass for an incompressible, ideal fluid: since no fluid is created or destroyed, the total mass of the fluid must be constant.

Back 2

1. Flow (Q)
2. Continuity Principle

Front 3

An ideal fluid is incompressible, undergoes laminar flow, and lacks viscosity
1. expression of conservation of energy applied to ideal fluid flow.

Back 3

1. Bernoulli's principle

Continuity equation:
Q = A1V1 = A2V2 ==> an increase in A leads to a drop in velocity

Front 4

Total cross sectional area comprises all parallel vessels of that type
1. The driving force for blood flow through a blood vessel is dependent on what?

Back 4

1. Pressure differences rather than absolute pressure

Front 5

1. What is defined as a perpendicular force applied over an area?
2. What is a gauge pressure?

Back 5

1. Pressure units: mmHg or CmH20
2. A pressure measured over the atmospheric pressure over 760 (i.e. zero is set to actual 760 mmHg)

Front 6

Transmural vs Hydrostatic vs Perfusion Pressure
1. difference between arterial (Pa) and venous (Pv) pressures across individual organs or across systemic (aorta to vena cava) or pulmonary (pulmonary artery to pulmonary vein) circulations
2. because of gravity, fluid (blood in the vascular system) has weight that generates force. The force is proportional to the vertical height of the fluid exposed to gravitational conditions and is determined by the equation: Ph= ρgh

Back 6

1. Perfusion (driving) pressure delta P
2. Hydrostatic pressure (Ph)
ρ = density of fluid (g/cm^3)
g = gravitational constant
h = ht of fluid column above reference level

Front 7

Transmural vs Hydrostatic vs Perfusion Pressure
difference between intravascular pressure (inside vessel, Pi) and extravascular (outside vessel, Po) pressure. In many organs under resting conditions, extravascular pressure, Po, is 0; but this will
be more important under conditions leading to edema. Since vessels are distensible rather than rigid tubes, transmural pressure can help regulate vessel
diameter

Back 7

Transmural pressure

Front 8

1. What is the baseline reference level in the CV sys?
2. is intravascular pressure below the hrt increased or decreased?

Reference level for mean arterial pressure for a. and v. is 95 mmHg; and 2 mmHg in the vena cava near the hrt

Back 8

1. The heart
2. Increased - above the heart is decreased

Front 9

1. What position of the body eliminates the hydrostatic effect?
2. a cm of water = how many mmHg?
3. What is the perfusion pressure in the foot standing? lying down? artery pressure = 90, vein pressure = 5

Back 9

1. Supine/recumbent
2. 1.36
3. 85 mmHg

Gravity has an equal effect on arterial and venous pressures and doesn't change A-V pressure difference

Front 10

1. Measuring BP at the zero reference is imp b/c?
2. Which vessels can Bernoulli's equation be applied?

Total energy = P1 + density * velocity^2 / 2
P1 = PE ;; and density* velocity^2/2 = KE

Back 10

1. it eliminates the hydrostatic effect
2. Large a. b/c energy loss due to viscosity is low and velocity is relatively high

KE causes the impact pressure; = the amount of pressure required to make flow stop

Front 11

1. PE is due to what?
2. Is KE or PE measured with the BP cuff?
3. What is the baseline arteriolar pressure in heart and feet? (venous?)

Back 11

1. the work of the contracting heart (lateral pressure x volume)
2. PE - the lateral pressure - pressure that distends vessels
3. 90 (5) mmHg

Front 12

Bernoulli's clinical applications:
1. Arterial narrowing - decrease radius -> increase velocity -> decrease pressure which leads to narrowing further of the lumen
2. Aneurysm - ballooning out, increase radius -> decrease velocity -> increase lateral pressure, ballooning gets worse

Back 12

KE = mass * velocity^2 / 2
PE = pressure x volume = work/volume

Front 13

1. Resistance in a vessel is equal to what?
2. Which vessel has the greatest resistance to blood fow

Q = dP * pi * r^4 / (8 * viscosity * length)
Q = dP / R

Back 13

1. 8 * viscosity * length / (pi * r^4)
2. Arterioles

Front 14

Dilation vs Constriction of arterioles
1. increases local resistance and intravascular pressure above XXX site; decreases pressure downstream in capillaries & local blood flow
2. decreases local resistance and intravascular pressure above XXX site; increases pressure downstream in capillaries & local blood flow

Back 14

1. Constriction
2. Dilation

Series resistance - add
Parallel resistance - total resistance is always less than the individual resistance

Front 15

1. What is the major factor that changes the viscosity of the blood?

Back 15

1. hematocrit - can be due to polycythemia, dehydration, loss of plasma from burns, loss of water through renal sys.

Front 16

1. What are 3 situations in which reynolds number predicts turbulence?

Back 16

1. Anemia - decreases viscosity and increases velocity
2. Atherosclerotic plaque - decrease cross-sectional area and increases v
3. Korotkoff sounds: blood pressure cuff measurements