Ch. 18 Physics: Hemodynamics Flashcards
THE STUDY OF BLOOD MOVING THROUGH THE CIRCULATORY SYSTEM
Hemodynamics
Volume of blood at a particular time
Flow (volume flow rate)
Speed of fluid from one location to another
Velocity
How is flow rate measured?
volume/time
How is velocity measured?
distance/ time
Looking at the monitor what the is peak velocity abreviation?
PS
Looking at the monitor what is the velocity flow rate located?
Bottom where it says VolFlow
What are the 3 type of flow?
Pulsatile
Phasic
Steady
What is pulsatile flow rate?
Variable velocity
Changes with cardiac contractions
Usually, arterial
What is phasic flow rate?
ariable velocity
Changes with respiration
Usually, venous
What is steady flow rate?
Constant velocity
Often in venous flow when holding respiration
(or upstream obstruction)
The way blood flows through vessels can be described as _________ or __________
laminar or turbulent.
predicts whether flow is laminar or turbulent.
Reynolds number
“Silent flow”, Flow streamlines are aligned and parallel, and Layers of blood in a vessel travel at individual speeds all describe what?
Laminar flow
What are the 2 forms of laminar flow?
PLUG FLOW
PARABOLIC FLOW
What is plug flow?
all layers travel at the same speed
What is parabolic flow?
highest velocities in the center, decreases closer to the vessel wall
Chaotic flow pattern traveling in many different directions and speeds, Eddy current (vortex) – hurricane-like, swirling, rotational patterns, Often associated with pathology, is all describing what kind of flow?
Turbulent
Which flow converts flow energy into sound and vibrational energy?
Turbulent
When turbulent flow is present how is the sound described? how is the vibration described?
bruit
thrill
What is it called Blood moves from higher energy to lower energy and Energy is imparted onto the blood stream by the left ventricle?
Energy gradient
What are the 3 different forms of blood energy?
Kinetic
pressure
gravitational
What is it called when all 3 forms of blood energy are combined?
Total energy
True or false:
Energy gradient Cannot be created or destroyed, only transferred.
true
MOVING OBJECTS and DETERMINED BY MASS and SPEED describes what kind of blood enery?
Kinetic
STORED (POTENTIAL) ENERGY, ABILITY TO PERFORM WORK, MAJOR FORM OF ENERGY FOR BLOOD CIRCULATION, all describes what kind of blood energy?
Pressure
STORED (POTENTIAL) ENERGY, ASSOCIATED WITH ANY ELEVATED OBJECT, IDENTICAL OBJECTS AT THE SAME HEIGHT HAVE THE SAME GRAVITATIONAL ENERGY, all describes what kind of blood energy?
Gravitational
What is another term when we say that energy is lost?
transferred
What are the 3 ways energy is lost?
Viscous
Frictional
Intertial
THICKNESS OF FLUID (HONEY VS WATER) and is Measured in units of Poise
Viscosity
Amount of energy loss in blood is measured by
hematocrit
What is hematocrit?
% of blood made up of RBC’s
True or false:
MORE ENERGY IS LOST WITH HIGH VISCOSITY LIQUIDS
True
FLOW ENERGY IS CONVERTED TO HEAT AS OBJECTS RUB AGAINST EACH OTHER is what kind of loss of energy?
Frictional
ENERGY IS LOST WHEN SPEED CHANGES and OCCURS DURING 3 EVENTS; PULSATILE FLOW, PHASIC FLOW, STENOSIS, describes what kind of loss of energy?
intertial
NARROWING IN THE LUMEN OF A VESSEL
stenosis
How does stenosis affect blood flow?
CHANGES IN DIRECTION
INCREASED VELOCITY WITHIN STENOSIS (HIGHEST WHERE NARROWEST)
POST-STENOTIC TURBULENCE
What kind of currents fill the vessel when the lumen expands after stenosis?
Eddy
High pressure pre-stenosis, low pressure post-stenosis, describes what?
pressure gradient across stenosis
Where is velocity highest in stenosis?
At the most narrow segment
Where is turbulent blood flow seen in stenosis?
Distal to the narrowing
What happens post stenosis?
loss of pulsatility
DESCRIBES THE RELATIONSHIP BETWEEN VELOCITY AND PRESSURE IN A MOVING FLUID and IS DERIVED FROM THE LAW OF CONSERVATION OF ENERGY
BERNOULLI’S PRINCIPLE
AS PRESSURE ___________, VELOCITY DECREASES
INCREASES
they are inversely related
what is the formula for when THE PRESSURE GRADIENT INCREASES IF FLOW OR RESISTANCE INCREASES?
PRESSURE GRADIENT = FLOW (Q) X RESISTANCE (R)
What is the formula for when THE FLOW INCREASES WHEN THE PRESSURE GRADIENT INCREASES OR RESISTANCE DECREASES?
FLOW (Q) = PRESSURE GRADIENT/ RESISTANCE (R)
RESISTANCE INCREASES WITH
THE LENGTH OF THE TUBE
VISCOSITY
RESISTANCE DECREASES WITH:
DECREASED RADIUS
DESCRIBES THE WAY ELECTRICITY FLOWS THROUGH A WIRE.
SIMILAR TO HOW BLOOD FLOWS THROUGH A VESSEL
Ohm’s law
OHM’S LAW STATES THAT:
VOLTAGE = CURRENT X RESISTANCE
(PRESSURE = FLOW X RESISTANCE)
VEINS HAVE THIN, COLLAPSIBLE WALLS THAT CHANGE SHAPE WITH __________.
PRESSURE
In venous hemodynamics, IN A LOW-PRESSURE SETTING, THE WALLS WILL ____________.
collapase
In venous hemodynamics, IN A HIGH-PRESSURE SETTING, THE WALLS WILL _________.
expand
DURING EXERCISE, THE VEINS EXPAND creating what?
LOWER RESISTANCE AND INCREASE IN VESSEL DIAMETER
INCREASE IN VESSEL DIAMETER means what?
INCREASE IN FLOW TOWARD THE HEART
what is the formula for hydrostatic pressure?
Hydrostatic pressure (P)= height (h) x gravity (g) x density of blood (p)
PRESSURE RELATED TO THE WEIGHT OF BLOOD PRESSING ON A VESSEL, MEASURED AT A HEIGHT ABOVE OR BELOW THE HEART
Hydrostatic pressure
BLOOD PRESSURE IS ACCURATELY ASSESSED AT THE LEVEL OF THE ___________.
heart
what is the measurements of hydrostatic pressure?
units of mmHg
What is the level of hydrostatic pressure at heart level?
0
True or false:
If the body is in supine position, hydrostatic pressure will be 0 through out the body regardless of where it is taken.
True
If the patient is standing, hydrostatic pressure below the heart is what? positive or negative?
Positive, it will be higher than actual circulatory pressure
If the patient is standing, hydrostatic pressure above the heart is what? positive or negative?
Negative, it will be lower than actual circulatory pressure
Venous flow is affected by
respiration
What are the two reasons venous flow is affected by respiration?
Venous system is low pressure
Muscles responsible for respiration (diaphragm) alter pressures in the thorax and the abdomen
Two venous flows affected by respiration
Venous flow in the legs
Venous flow returning to the heart from the head, arms, and IVC
Decreased thoracic pressure
Increased upper extremity venous flow
Increased abdominal pressure
Decreased lower extremity flow
This describes inspiration or expiration in venous hemodynamics?
Inspiration
Increased thoracic pressure
Decreased upper extremity venous flow
Decreased abdominal pressure
Increased lower extremity flow
This describes inspiration or expiration in venous hemodynamics?
Expiration