5AD Flashcards
what is electricity?
movement of a charge from positive to negative
what is an example of chemical charge
batteries
what is an example of physical charge
friction from socks and carpet
what is an example of biological charge
movement of discharge
what is Ohm’s law?
the potential difference in an electrical conductor is proportional to the current in the conductor
what is Ohm’s law used to do
used to calculate electrical values so that we can design circuits and use electricity to suit our needs
what is voltage
a measurement of the work required to move a unit charge between two points
what is current
the measurement of the flow of charge in a circuit
what is resistance
the measure of the amount of current repulsion in a circuit
what is the equation for Ohm’s Law?
V = I x R
what is capacitance?
the ability of a body to store an electrical charge
what is the relationship between capacitance and electrical charge
a material with a large capacitance holds more electrical charge at a given voltage, than one with low capacitance.
how does the electric activity in living tissue work?
- dependent on cell membrane
- the cell membrane acts like a capacitor, storing energy as electrically charged ions on opposite sides of the membrane
amplifiers
modulates the output of the power supply to make the output signal stronger than the input signal
why was a Wheatstone bridge created?
to measure unknown resistance values
can be used to measure very low values of resistance
what are some currents that we measure within living organisms
- active cells
- muscle contractions (ex heart)
- nerve impulses (ex brain)
what does the electrocardiogram (ECG/EKG) record?
records the electrical activity of the heart, providing a record of cardiac electrical activity as well as valuable info about the heart’s function and structure
the electrodes on the skin used in medical tests measure voltages of ____ mv
< 1 mv
what is electroencephalogram (EEG)
a test that detects electrical activity in your brain using small, flat metal discs attached to your scalp
-brain cells communicate via electrical impulses and are active all the time, this activity shows up as wavy lines on an EEG
transduction
the action or process of converting energy or a message into another form
what is the measure of real-world physical conditions and converting the resulting samples into digital numeric values is known as
signal/data acquisition
what is an example of signal/data acquisition?
EKG and mechanical transducers
where are electrons placed?
brain, chest, muscles
mechanical transducers
are the mechanical elements that are used for converting one form of energy into another form that can be measured easily
pressure transducers
convert fluid/air pressure into an electrical signal
what is the operation principle behind the electromagnetic blood flow meters
Faraday’s law which states that if electrical current carrying conductor moves at right angle through a magnetic field, an electromotive force is induced in the conductor
what produces a flow in the elctromagnetic flow meter
voltage induced in the conductor gives you the velocity of the conductor
what is the pro/con on the electromagnetic flow meter
more precise but invasive and large
what type of flow meter is an ultrasonic flow meter
measure the velocity of a fluid with ultrasound to calculate volume flow
what is the pros/cons to the ultrasonic flow meter
- smaller and non-invasive and can now be used in conjunction with a bubble detector
- most commonly used
- It gives you an average and does not measure the highest velocity of flow (laminar flow)
how can electrostatic potentials be generated?
can be generated during bypass procedures using PVC tubing in a roller pump
electrostatic potentials can produce in excess of ___ DC V
600 DC V
what are the risks of electrostatic potentials
- can lead to a misdiagnosis of arrhythmias
- misinterpreted as real heart activity during CPV leading a physician to give more anesthetic agents or administer more cardioplegia
what are some prevention methods to electrostatic potentials?
- be aware of the problem as to prevent misdiagnosis
- ground the pump properly to discharge electrostatic potential
- make sure the patient is properly cleaned, electrodes placed accurately and OR table grounded
what is digital signal processing (DSP)
the numerical manipulation of signals, usually with the intention
what is the process of how all those transducers, pressure, and electrode sensors turn the measure outputs into a Digital reading on the monitor
analog signal
ADC (analog digital convertor)
digital signal processing
DAC (digital analog convertor)
analog signal
what is the biophysical transport phenomenon
how a fluid (blood) reacts in a studied environment in relation to momentum, mass, energy such as fluid dynamics and thermodynamics
what do biophysical transport phenomenon help us understand?
understand how blood is reacting within our circuit, and how these principles are being used to further develop better perfusion technology
ideal blood will have ____ flow through the circuit with little ___, little ____, and minimal ___ ____.
ideal blood will have laminar flow through the circuit with little resistance, little turbulence, and minimal shear forces
adverse effects on flow and blood
- increasing speed
- pressure drops
- changing in circuit dimension
- changing in patient temperature
what law do we use as a reference to calculate current and translate it into flow
Ohm’s Law
I = delta V / R
under ideal conditions, what kind of flow is within the vessel (and/or tubing)
laminar flow
what is laminar flow
when a fluid flow in parallel layers, with no disruption between the layers
at low velocities, where is the highest and lowest velocities
highest velocity in the centerline
lower velocities towards the wall of the vessel
an increase in resistance will do what to the flow and pressure
increase in resistance will decrease in flow and increase in pressure
decrease in resistance will do what to the flow and pressure
decrease in resistance will cause an increase in flow and decrease in pressure
what is the determining factor of fluid dynamics
resistance
what will change the resistance in the vessel
change in size (diameter) of the vessel or obstruction
what will change the resistance in the circuit
tubing changes and different filters and the oxygenator
could create a pressure drop
to understand resistance, what equation is used
Poiseuille’s equation
Q = pie Pr^4 /8nl
there are three primary factors that determine the resistance of blood flow within a single vessel. They are…
vessel diameter
vessel length
viscosity
what is the take home regarding the Bernoulli equation?
blood flowing at higher velocities has a higher ratio of kinetic energy to potential (pressure) energy
what is an example of Bernoulli equation
when you put your finger over a hose
how does blood flow in nature?
chaotic, which increases the energy to drive blood flow
where can turbulent flows occur?
aorta, branch points, stenotic vessels, and on the circuit at connector change
when does turbulence flow begin to occur?
does not begin to occur until the velocity of flow becomes high enough that the flow lamina break apart
what is the breaking point number that indicates the point at which turbulence flow will occur?
Reynolds number
what RE indicates turbulent flow?
RE of 4000 and above
Poiseuille’s law is only applicable in conditions of _____ flow.
laminar
where can significant turbulence be found on the circuit?
oxygenator
dimples in the hollow fiber can cause ____ _____.
eddy currents
what do eddy currents in the oxygenator allow for?
allows for greater dwell time for oxygen transfer to occur
viscosity definition
a property of fluid related to the internal friction of adjacent fluid layer sliding past one another as well as the friction generated between the fluid and wall of the vessel
viscosity has a direct link to
shear stress
changes in viscosity can be due to
- hematocrit
- temperature
- shear rate
as hematocrit increases, there is an _____ in viscosity
as hematocrit increases, there is an increase in viscosity
as temperature increases, viscosity ____
increases
for every 1 c decrease there is a 2% viscosity increase
what is the relationship between shear rate and viscosity
at very low shear rates in the blood, blood viscosity can increase significantly
conduction
transfer of heat between substances that are in direct contact with each other
convection
movement cause within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity
radiation
electromagnetic waves come in contact with an object the waves transfer heat to the object
heat exchangers use all three forms of heart transfer but mainly through
conduction and convection
what is a good conductive material?
plastics or stainless steel
how does the pump use forced convection?
by actively pumping the fluid through the exchanger in a counter current movement
leakage current
current that flow through the protective ground conductor to ground
what happens when the machine is not properly grounded?
leakage current
what is line isolation system
gives you a reading of how much connection there is between the supposedly isolated wall power wires, and earth ground
what is equipotential grounding system
bonding of all conductive surfaces in the room together and to earth.
what shuts off a circuit if a break in the current is detected?
ground fault circuit interrupters (GFCI)
what is radiology
a branch of medicine concerned with the use of radiant energy or radioactive material in the diagnosis and treatment of disease
what is the oldest and one of the most common clinical test used in hospitals?
xray
what is fluoroscopy?
imaging technique that uses X-rays to obtain real time moving images of the interior of an object
-picks up contrasts, barium, iodine, and air to help pin point internal structures
angiography
a medical imaging technique used to visualize the inside, or lumen, of blood vessels and organs of the body, with particular interest in the arteries, veins, and the heart chambers
ex: left heart Cath
what is digital subtraction angiography (DSA)
type of fluoroscopy technique used in interventional radiology (IR) to clearly visualize blood vessels in a bony or dense soft tissue environment
what is the process of digital subtraction angiography?
takes a picture of the tissue
takes a second picture with contrast injected
then the first picture is subtracted to visualize the vessels
what does CT stand for
computed tomography
how does CT differ from X-ray
like X-ray but the multiple images (slices) can be placed together to create a 3D picture of the organ in question
what is nuclear medicine?
medical imaging that uses small amounts of radioactive material to diagnose and determine the severity of or treat a variety of diseases
what radioactive materials are used in nuclear medicine?
radoopharmaceuticals or radio tracers
what is a nuclear stress test?
a nuclear stress test is a diagnostic test used to evaluate blood flow to the heart
what radioactive material is used in a nuclear stress test
Tc-99 (radioactive isotope)
what is multiple gated acquisition scan? (MUGA)
designed to evaluate the function of the right and left ventricles of the heart
produces a moving picture of beating heart to evaluate EF
what radioactive isotope is used in MUGA scans?
Tc-99
what is a V/Q scan
two tests that measures air and blood flow in your lungs
why are V/Q scans mainly done?
to see if pulmonary embolisms or atelectasis
During the ventilation phase of the test, what gaseous radionuclide is inhaled in an aerosol form by the patient?
xenon or technetium DTPA
Perfusion scans are doing by injecting _____ and then takin pictures of the ____ to see if _______
Perfusion scans are doing by injecting Tc-99 and then taking pictures of the lungs to see if a PE is present
Pictures of a V/Q scan are taken with what kind of camera?
gamma camera
what does PET scan stand for
Positron Emission Tomography
what does PET scans show that CT or MRI doesn’t
shows problems at the cellular level
what does PET scan measure
blood flow, oxygen use, glucose metabolism (how your body uses sugar)
PET scans are most commonly used to detect
- cancer
- heart problems
- brain disorders
- problems with the CNS
radionuclides used (7)
- carbon-11
- nitrogen-13
- oxygen-15
- fluorine-18
- gallum-68
- zirconium-89
- rubidium-82
what is echocardiography
sonogram of the heart by using standard 2D, 3D, and doppler US to create images of the heart
is ECG an abbreviation for echocardiography
NO
how can echocardiography be done?
transthoracic (TTE)
or
transesophageal (TEE)
what is echocardiography used to asses
wall motion
valve movements
blood flow
and other structural assessments of the heart
what is the color on echocardiography used for
to see the direction of blood flow, laminar flow, and turbulent flows
what is MRI
test that uses a magnetic field and pulses of radio wave energy to make pictures of organs and structures inside the body
in MRI, the transfer of electric energy to magnetic energy is govern by what law
Faraday’s Law of induction
what’s special about MRI
does not use radiation
what problems does MRI detect
tumors, bleeding, injury, blood vessel disease, infection
