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Monitoring of CV Patient I > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

Conventional Current

A

Flows in opposite direction of electrons (positive to negative); direction does not affect what current does

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2
Q

Electricity

A

Invisible force that can produce heart, light, motion by attraction or repulsion, and many other physical effects; flow of electrons around a circuit form (-) to (+)

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3
Q

Coulomb (C)

A

derived unit of electric charge (Q) defined as charge transported by a constant current of one ampere in one second

6.25 X 10^18 electrons= 1 coulomb (-) charge
1 electron has charge 0.16 x 10^-18 C

6.25 X 10^18 protons = 1 coulomb (+) charge
1 proton has a charge of 0.16 x 10^-18 C

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4
Q

Charge Movement Units

A

Joule- passing electric current of one ampere (A) through a resistance of one ohm for one second (1 Nm)

Watt- 1 J/second energy rate of transfer

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5
Q

Voltage (V)

A

Work per unit charge against a static electrical field; potential difference found in any field (gravitational, magnetic, electric). Units for electric: V; Units for gravity: J/kg; measures difference between 2 circuit points; can be positive or negative

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6
Q

Voltage Drop

A

describes how supplied energy of a voltage source is reduced as electric current moves through the passive elements (elements that do not supply voltage) of an electrical circuit

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7
Q

Current (I)

A

movement of charge (charge/sec)/ electrons; flow of charge; how much charge flows past a given point in a given period of time; occurs most easily in good conductors

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8
Q

Resistance (R)

A

opposition to the movement of electrons; describes how much difficulty electrons feel as they are forced to move in a net direction through the material

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9
Q

Conductors

A

electrons move easily from atom to atom; allows electrons to move (current) with minimal opposition; low resistance

Ex. silver/copper/ 0.9% saline, electrolyte solutions

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10
Q

Insulators

A

electrons tend to stay in own orbits- cannot conduct electricity; high resistance; able to store or hold electrons better than conductor (capacitor)

Ex. glass/ plastic/ rubber/ paper/ air

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11
Q

Semiconductor

A

pass more electronics than insulator but less than conductor

Ex. carbon/ germanium/ silicon

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12
Q

Direct Current Voltage (DC)

A

flow of charge in one direction and the fixed polarity of the applied voltage; can be steady or vary in magnitude; electricity loses power within about a mile of release from power station

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13
Q

Alternating Current (AC)

A

polarity periodically reverses or alternates- flow of charge reverses as the polarity changes; varies in magnitude between reversals in polarity; makes a complete wave 60 times each second so effect of current and voltage dropping to a negative value is not visible without oscilloscope; high voltages over long distances (less voltage drop); power devices requiring 120V or 240V

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14
Q

Law of the Conservation of Energy

A

The total energy of an isolated system cannot change- it is said to be conserved over time. Energy can be neither created nor destroyed, but can change form; ex. chemical energy can be converted to kinetic energy

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15
Q

Hemodynamics

A

Physical factors that govern blood flow

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16
Q

Poiseuille’s Law

A

R = (Lxnx8)/ Pi*r^4

Assumptions: radius is uniform; flow is laminar

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17
Q

Reynold’s Number

A

dimensionless quantity whose magnitude gives an indication of whether flow is laminar or turbulent

Re= mean velocity * density * diameter/ Viscosity
Re < 2000 : flow likely laminar
Re > 2500: flow is likely turbulent

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18
Q

Series Equations

A

V1+V2+V3
I1=I2=I3
R1+R2+R3

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19
Q

Parallel Equations

A

V1=V2=V3
I1+I2+I3
1/ [ (1/R1) + (1/R2) + (1/R3) ]

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20
Q

Electrical Autoregulation

A

The opening of channels and gates (Na + and K +) both actively and passively allow equilibrium to be maintained in the presence of acute and chronic disease states

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21
Q

Why is electricity dangerous?

A

Tissue injury; uncontrollable muscle contraction or unconsciousness; fibrillation of heart; polarized cells at rest can be stimulated to depolarize by mechanical, chemical, thermal, optical, and electrical stimulation

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22
Q

Electrical Safety

A

containment or limitation of hazardous electrical shock, explosion, fire, or damage to equipment, buildings or personnel; scope involves potential microshocks from any electrically operate device that can come into contact with the patient

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23
Q

Leakage Current

A

current that inherently passes or flows from the energized electrical portions of the device to the metal chassis and then to earth ground; natural consequence of electrical wiring and components; all electrical equipment has it

Not functional current; unwanted; occurs with improperly grounded electrical equipment

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24
Q

Macroshock

A

high- value arm to arm current (milliamps) that eventually passes through the heart- may cause v fib

5 mA (below “Let-go” threshold”

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25
Microshock
low-value current that passes directly through the heart via in-dwelling needle or catheter 10 uA is considered dangerous
26
How to Reduce Chance of Microshock
Reduce internal leakage below 10uA Monitor ground wire continuity (LIM)/Inspect integrity Power-isolated system Equipotential Ground System (separate connections from each equipment chassis to common ground terminal; add ground wire from chassis to central point) Ground Fault Interrupter (automatic switch cuts power if excessive leakage detected) Test and maintain all equipment regularly
27
Line Isolation Monitor (LIM)
Predicts "next fault;" Monitors impedence (AC Resistance); alarm will signal next fault danger
28
Impedence
AC Resistance
29
Biometrics
Science that includes the measurement of physiological variables and parameters; provides the tools by which measurements are made
30
Biomedical Instrumentation
Marriage of medicine and engineering
31
Types of Physiological Measurements
Passively (EKG) Require Application of Energy (Pressure tracing) Reflection/Refraction of Light (Saturation/HCT monitors)
32
Range
All levels of input amplitude and frequency over which device expected to operate; usable reading from smallest expected value of parameter to largest
33
Sensitivity
How small a variation of a parameter can be reliably measured; how small of change can be detected; determines resolution (minimum variation that can be measured) Ratio: Amplitude of output vs Amplitude of input
34
Linearity
The degree that variations in the output follow variations in the input (one increasing along with another). If linear- sensitivity is the same for all levels of input (high, middle, or low)
35
Hysteresis
From Greek- hysterein- to be behind Output values obtained as the input value is increasing will differ from output values obtained as the input value is decreasing Response variable depending on input (fluctuations); negative feedback/variable response
36
Frequency Response
Variation in sensitivity over the frequency range of the measurement; affects ability to reproduce a waveform that is a faithful reproduction of the original; system should respond quickly enough to reproduce all frequency components of the waveform with equal sensitivity
37
Frequency response profile
Ratio of output amplitude/input amplitude over a range of frequencies of the input pressure; frequency response of a catheter system is dependent on catheter natural frequency and amount of damping The higher the natural frequency (Fn) of the system, the more accurate the pressure measurement at low frequencies
38
Types of Error
Range Tolerances of electronic components Mechanical errors in meter movements Component errors due to drift or temperature variation poor frequency response changes in ATM pressure or temp Improper Zeroing and/or calibration Perfusionist interpretation
39
Signal-To-Noise Ratio
Should be as high as possible (Signal/Noise)
40
Sources of Noise
Power-line frequency noise or interference (very common; picked up in long lead lines) Electromagnetic Electrostatic interference from other devices Leakage current
41
Stability
Ability of system to resume steady-state condition following disturbance at input rather than send system into uncontrollable oscillation; depends on amplification, feedback and other electronic features
42
Isolation
make measurement in a way that the instrument does not produce a direct electrical connection between the patient and the ground Electrical isolation to prevent leakage current Telemetry when need "lead" isolation
43
Simplicity
Reduce change for component of human error | Simple Reference Device- transducers calibrated at the factory
44
Electrodes
Device that is able to measure/ capture the appropriate biopotential and send the resultant electronic signal to the signal conditioning equipment (monitor); electrical conductor used to make contact with a nonmetallic part of circuit; collector or emitter of electrical charge or of electric-charge carriers
45
Transducer
Converts a non-electrical physical force (pressure, temp) to an analogous electric signal that is proportional to the value of the original mechanical to electrical conversion; utilize strain gauge and wheatstone bridge to determine the pressure applied to a diaphragm
46
Electrode Problems
``` High impedence (resistance) of human skin 10 k ohms (damp) to 500 k ohms (dry) ``` Movement artifact- slippage of electrode
47
Types of Pressure Transducers
Fiber Optic- not dependent on fluid; cannot calibrate after insertion (Ex. ICP monitoring) Fluid Filled- disposable or reusable; fluid dependent; accurate transducer to catheter tip; most accurate with fluid less with air; mean P does not change
48
Fluid Filled Systems Must Be...
Zeroed- reference baseline value Leveled- Equalize catheter tip and transducer; use phlebostatic axis (4th ICS) Calibrated- precalibrated when manufactured)
49
Components in Fluid Filled P Monitoring System
``` Transducer (electromechanical value) Pressure tubing Pressure bag (pump to higher P than patient) Crystalloid Amplifier Oscilloscope/Monitor ```
50
Strain Gauge
Pressure transducer that is rugged, accurate, and stable; operate in severe shock and vibration; can be glued to transducer assembly, when it is deformed it changes R
51
Piezoresistivity
describes the changing resistivity of a semiconductor due to applied mechanical stress
52
Types of Strain Gauges
Unbonded- linear over large range of inputs, delicate | Bonded (we see these)- rugged, small linear range of inputs
53
Wheatstone Bridge
electrical circuit measuring unknown R by balancing two legs of a parallel circuit; consists of 4 resistors used to determine the value of an unknown R when other 3 are unknown
54
Pressure Wave Signal Path
Pressure wave, transducer, strain gauge changes R, wheatstone bridge, monitor signal
55
Artifact
false signals superimposed on true signal
56
Calibration
standardization of measuring instrument: the checking of a measuring instrument against an accurate standard to determine any deviation and correct for errors
57
Catheter Whip
movement of catheter tip within the blood vessel in response to pulsatile flow
58
Damping
loss of energy and vibrations within the monitoring system
59
Dynamic Response
systems ability to measure physiologic pressure changes; testing ability of system to faithfully reproduce the patient's pressure on the monitor; may be tested using a square wave test
60
Fidelity
indication of system's capacity to faithfully reproduce the physiologic event
61
Natural Frequency
frequency at which the system vibrates when stimulated by pulsatile signals
62
Overshoot/Undershoot
system vibration that occurs when the patient's pressure wave contains a component frequency equal to the system natural frequency
63
Ringing
multiple small spikes on the waveform due to inadequate dynamic response characteristics
64
Cardiovascular System: 3 types of pressure
Hemodynamic Kinetic energy Hydrostatic
65
6 Physical Principles
I. Hydrodynamic Pressure II. Effect of Inertia III. Effects of Frequency response and natural freq. IV. Dynamic Response Testing (snap test) V. Orientation of the Catheter during measurement VI. Zeroing, Leveling and Calibration of the System
66
Hydrodynamic Pressure
pressure exerted by fluid in motion
67
Natural Frequency
Frequency at which fluid oscillates in a catheter when it is trapped Frequency of an input pressure wave at which the ratio of output/input amplitude of an undamaged system is maximal
68
Underdamping
Compliant pressure tubing; decrease natural frequency of system; if waveform contains harmonic equal to lowered natural frequency- overshoot with ringing; if severe, will get undershoot
69
Overdamping
component frequency exceeds frequency response of the system; portions of waveform dependent on those frequencies will be blunted and obscured
70
Resonance
the tendency of a system to oscillate at a greater amplitude at some frequencies than at others
71
System Characteristics to Reproduce Waveforms
Amplitude linearity Adequate bandwidth Phase linearity
72
System Characters you DO NOT want to Reproduce Waveforms
``` Phase Distortion (phase shift) Underdamping Overdamping Resonance Catheter Whip ```

Monitoring of CV Patient I (4 decks)

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