Circulatory Hemodynamics & Systemic and Pulmonary Circulation Flashcards
circulation can be divided in
Systemic circulation (greater circulation or peripheral circulation)
Pulmonary circulation or central circulation
percentage of circulation in the pulmonary circulation
9
percentage of circulation in the veins, venules and venous sinuses
64
percentage of circulation in the arteries
13
percentage of circulation in the heart
7
What is the path of blood flow?
systemic arteries-systemic capillaries-systemic veins
What is the function of systemic circulation?
Carries oxygenated blood from the left side of the heart through the systemic arteries to all the organs and tissues.
What happens after O2 is delivered to organs and tissues on the path of systemic circulation?
After delivering oxygen and receiving carbon dioxide in the systemic capillaries, returns deoxygenated blood through the systemic veins to the right atrium where the pulmonary circulation begins
What is the range of pressure in systemic circulation?
70-105 mmHg
relatively high pressure system
What are the methods used to measure systemic circulation?
a blood pressure cuff.
Invasive methods using telemetry and catheters
path of blood flow in pulmonary circulation
Right atrium-Right ventricle-Pulmonary arteries-Pulmonary capillaries Pulmonary veins-Left atrium- Left ventricle
function of pulmonary circulation
Carries deoxygenated blood from the right side of the heart through the pulmonary arteries to the lungs.
What happens after O2 is received and CO2 is delivered in the pulmonary capillaries during pulmonary circulation?
Returns oxygenated blood through the pulmonary veins to the left atrium where the systemic circulation begins.
pressure in the pulmonary circulation
relatively low-pressure system
10-22 mmHg
how is pulmonary circulation measured
using pulmonary artery catheters
arteries
transport blood at a high pressure to tissues -their walls are strong and blood flows rapidly.
arterioles
Control valves for capillary beds, through which blood is released into the capillaries.
Have strong muscular walls and the capacity to completely dilate or close, thereby altering the blood flow to the tissue.
capillaries
High surface area for maximum transfer between blood and interstitium.
This area is where nutrients are exchanged.
Its walls are thin, and it has numerous pores through which fluid and electrolytes are exchanged.
venules
drainage from capillaries
veins
Transport conduits back to the heart and storage reservoirs for blood.
The pressure in the venous system is low, so the walls are thin, but they can contract and expand, thereby acting as reservoirs to hold extra blood depending on the tissue’s needs.
% of blood distribution in circulation
Systemic circulation 84%
Pulmonary circulation 16%
3 factors that contribute to Hemodynamics of Circulation
Blood flow
Resistance to blood flow
Blood pressure
Define the Ohm’s law of circulation
Blood flow occurs only when there is a difference in the pressure between the two ends of the vessel.
Define blood flow
the quantity of blood that passes a given point in the circulation at a given period.
t/f The overall blood flow in the systemic circulation is different from the cardiac output
false
it is identical
2factors affecting blood flow
The pressure difference between the two ends of the vessel
Resistance (frictional force produced when blood flows through blood vessels)
Define blood pressure
the force exerted by the blood against any unit area of the vessel wall
t/f Blood pressure is the stored energy (potential energy)
true
What 3 factors account for the generation of blood pressure?
ventricular contraction
total peripheral resistance
mean circulatory filling pressure
define perfusion pressure
As the blood moves through different parts of the circulation, it encounters different degrees of friction, which uses up energy and reduces blood pressure in various parts of the circulation.
Blood circulation dissipates
heat
t/f The aorta and large arteries offer minimal resistance, so blood pressure decreases very little.
true
What is the role of arterioles in terms of blood pressure and resistance?
They are the resistance vessels, and they offer a greater degree of resistance, hence there is a maximal drop in blood pressure
what is a characteristic of the pressure in the systemic and pulmonary circulation?
it is pulsatile
pressure in systemic capillaries, arteriolar end
35 mmHg
pressure in systemic capillaries, venous end
10 mm Hg
Functional pressure in the vascular bed is 17 mm Hg, this is important because
prevents leakage of plasma out of the pores of the capillaries even though nutrients can pass easily.
Why is the pressure in the pulmonary capillaries lower?
Due to the need of the tissue, oxygen and nutrients are exchanged between the capillaries and pulmonary alveoli.
blood travels a shorter distance than in the systemic circulation
3 circulatory cardinal points
blood flow to the tissue
cardiac output
arterial pressure
What 2 factors control the blood flow to each tissue?
Microvessels monitoring nutrients
nervous system
What 2 factors control the cardiac output?
the sum of all the local tissue flows
Automation
help from the nervous system
What 3 factors control arterial pressure?
independently of flow or cardiac output control
Baroreceptor
nervous system
kidneys-long term
3 factors that affect the Interrelationship between Pressure, Flow and Resistance
blood flow pressure gradient ( pressure difference between 2 ends if the vessel
vascular resistance (impediment of blood flow)
Ohm’s law
resistance of blood flow
the impediment to the flow of blood in a vessel
How is blood flow resistance measured?
indirectly
How do you calculate resistance?
dividing pressure/flow
Define laminar flow - parabolic flow profile
streamlined flow when the interior of the blood vessel is smooth and equal in diameter.
the outermost layer moves the slowest, and the center moves the fastest.
Define turbulent flow - non streamline with eddys
Interrupted flow occurs when the interior of the blood vessel is constricted and or rough.
creates sounds that may be indicators of constriction
What does Reynold # measure and what 4 factors is it based on?
Measures tendency for turbulent flow.
Based on:
flow velocity (v)
vessel diameter (d)
fluid viscosity (η)
density(ρ)
3 forms of measuring blood flow?
milliliters / minute
liters / minute
volume / time
2 methods of measuring blood flow
electromagnetic
ultrasonic
blood pressure is the force exerted by the blood against a
unit area of the vessel
When we say the pressure is 100 mm Hg, what are we referring to?
The force exerted is sufficient to push a column of mercury against gravity up to a level of 100 millimeters
Arterial and venous pressure can be measured in 2 ways
centimeters of water
millimeters of mercury (specific gravity of mercury is 13.6 times that of water)
blood pressure can be measured in 2 ways
Steady-state blood pressure measurement (mercury manometer)
Telemetry (rapid minute-to-minute changes)
How does the auscultatory method of arterial blood measurement work?
The cuff occludes artery flow when inflated, up to 200 mmHg
when cuff pressure falls below systolic pressure, blood will jet through the artery, producing Korotkoff Sounds
when cuff pressure falls below diastolic pressure, blood jetting will stop and Korotkoff Sounds will disappear
what cuases the Kortkoff sound?
Blood jetting through the partly occluded vessel.
The jet causes turbulence in the vessel, which creates vibrations that are heard by a stethoscope.
In arterial pressure measurement via the auscultatory method, what is the first Kortkoff sound related to?
systolic pressure
In arterial pressure measurement via the auscultatory method, what is the last Kortkoff sound related to?
diastolic pressure
Mean arterial pressure takes into account
systolic
diastolic
arterial
What range of accuracy does the auscultatory method have?
10%
t/f arterial pressure remains closer to systolic pressure during the cardiac cycle
false
closer to diastolic
% of systolic and diastolic pressure that determine mean arterial pressure
60% D
40 % S
define Total peripheral resistance (TPR)
Resistance to the flow of blood when the vessels are arranged in series or parallel, the flow of blood through each blood vessel is the same.
Total periphery resistance permits
each tissue to regulate its own blood flow independently of the other tissues
The rate of blood flow through the circulatory system is equal to the
the rate of blood pumped by the heart
TPR is calculated by
pressure / flow
TPR increases when
Vessels are constricted
TPR decreases when
Vessels are dilated
Total pulmonary vascular resistance is calculated by subtracting
Mean arterial pressure 16 mmHg and mean pulmonary vein pressure or left atrial pressure 2 mmHg = 14 mmHg
How do you calculate TPR?
MEAN AORTIC PRESSURE - MEAN VENACAVAL PRESSURE / CARDIAC OUTPUT
How do you calculate PVR (Pulmonary vascular resistance)?
MEAN PULMONARY ARTERIAL PRESSURE - MEAN PULMONARY VEIN PRESSURE (LEFT ATRIAL) / CARDIAC OUTPUT
BLOOD FLOW IS CALCULATED
PRESSURE DIFFERENCE / RESISTANCE
Arterial pressure is calculated
CARDIAC OUTPUT * TPR
DEFINE CONDUCTANCE
A measure of the blood flows through a vessel for a given pressure difference.
CONDUCTANCE IS DIRECTLY PROPORTIONAL TO
The diameter of the vessel.
HOW is conductance calculated
1 / resistance
Poiseuille’s law: flow decreases when what increases?
resistance increases
and vice versa
4 Factors affecting blood flow
hematocrit
blood viscosity
fahraeus-lindqvist effect
rouleaux formation
hematocrit
percentage of cells in blood
Blood viscosity is related to
the amount of plasma protein [ ]
Fahraeus-Lindqvist effect
responsible for decreased viscosity in small vessels
Rouleaux formation
Red cell adherence produces blockage of the vessel
t/f all blood vessels are distensible
true
The distensible nature of the arteries accommodates for 2 factors
The pulsatile nature of the blood flow
provides a smooth blood flow
vascular compliance (capacitance)
The tendency for blood vessel volume to increase as blood pressure increases
the more easily the vessel wall stretches, the greater its compliance -the venous system has a significant compliance
veins are also called the
blood reservoirs
How do you measure the relationship of pressure and volume In a blood vessel?
volume loop measurement
Infusion of blood or fluid into the venous system without any adverse effects
With volume loop measurement, you stimulate the SNS; what happens if the SNS tone increases or is inhibited?
Increased SNS tone increases pressure at each volume of the arteries and veins.
Inhibition of SNS tone decreases the pressure at each volume of the vessels.
Define delayed compliance or stress relaxation
A vessel exposed to increased volume initially exhibits a significant increase in pressure, but progressive delayed stretching of the vessel wall allows the pressure to return to normal.
delayed compliance is a method that serves for what kind of procedure does it serve?
blood transfusion
circulation can accommodate a large amount of blood when necessary
difference between distensibility and compliance
distensability = ability to return to the original level after distending force or pressure is removed.
Compliance = measure of how much of force is required to achieve distension, eIt it requires a high level to distense an artery
t/f each heart beat result is a surge of blood
true
distensibility allows for blood to flow during
systole and diastole
Compliance reduces the pressure pulsation, needed for
blood flow in the capillaries with little pulsation
pulse pressure Is the same as
difference between systolic-diastolic pressure
pulse pressure is felt by
placing a finger tip in the artery
ex. femoral a. in dogs
4 factors affecting pulse pressure and mechanism
stroke volume - larger ejection of blood = increase in mean arterial pressure = increase in pulse pressure
heart rate = decrease in heart rate decrease mean arterial pressure and cardiac output
arterial compliance = vessels stiffness
arteriolar vasoconstriction = blood accumulation in large arteries , distension, and stiffness of arteries
pulse pressure propagation
The rising pressure pulse in the central aorta overcomes inertia and the wave form of distension spreads further and further away from the aorta
How does compliance affect the velocity of the propagation of the pulse?
greater compliance = slower velocity of pulse pressure
is less as it is moving towards the capillaries
Where is the pressure velocity higher, in the aorta or in general blood flow?
aorta
2 factors that cause the damping of the pressure pulse propagation
Resistance to blood movement in vessels.
Compliance of the vessel
how to calculate damping
resistance * compliance
veins can
contract or relax
functions of veins
propel blood by means of the venous pump
regulate cardiac output
blood return from capillaries
A storage site for blood
what organs also serve to store blood?
spleen and liver
t/f venous pressure is the same as right atria pressure
true
Venous pressure or right atrial pressure (RAP) is a balance between
venous return
cardiac output
how is RAP affected is If the heart pumps strongly?
RAP DECREASES
how is RAP affected is If the heart pumps WEAKLY?
RAP INCREASES
FACTORS THAT AFFECT THE INCREASE OF VENOUS RETURN OR RAP
Increased blood volume
Increased large vessel tone resulting in increased peripheral venous pressure
Dilatation of arterioles, which decreases peripheral resistance
large veins =
little resistance to blood flow
compression of large veins in the thoracic and abdominal cavity
in the arms= compressed by angulation of first rib
neck = atmospheric pressure causes them to collapse
abdomen = compressed by organs
2 factors that cause RAP to increase
Blood begins to back up in the large veins and open them up.
hydrostatic pressure refers to the venous system, it is a
Column of fluid that produces a fluid pressure in extremities but also extends above the right atrium where negative pressures can exist (cranium).
venous valves functions
counter gravitation pressure effect
unidirectional flow back to heart
venous pump function
isolate the lower extremities from the edematous effects of high venous hydrostatic pressures
how are venous valves damaged?
over stretching of the veins by excessive venous pressure lasting for months
valves do not close completely
t/f Venous pressure can be estimated by looking at the degree of the distension of the peripheral veins.
true
What % of blood is stored in veins?
60
What happens when arterial pressure falls due to blood loss?
SNS is activated and blood is moved from blood reservoirs such as:
Spleen
Liver
Abdominal veins
Venous plexus beneath the skin
Heart
Lung
