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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
Q

Microshock

A

low-value current that passes directly through the heart via in-dwelling needle or catheter

10 uA is considered dangerous

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26
Q

How to Reduce Chance of Microshock

A

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

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27
Q

Line Isolation Monitor (LIM)

A

Predicts “next fault;” Monitors impedence (AC Resistance); alarm will signal next fault danger

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28
Q

Impedence

A

AC Resistance

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29
Q

Biometrics

A

Science that includes the measurement of physiological variables and parameters; provides the tools by which measurements are made

30
Q

Biomedical Instrumentation

A

Marriage of medicine and engineering

31
Q

Types of Physiological Measurements

A

Passively (EKG)
Require Application of Energy (Pressure tracing)
Reflection/Refraction of Light (Saturation/HCT monitors)

32
Q

Range

A

All levels of input amplitude and frequency over which device expected to operate; usable reading from smallest expected value of parameter to largest

33
Q

Sensitivity

A

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
Q

Linearity

A

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
Q

Hysteresis

A

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
Q

Frequency Response

A

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
Q

Frequency response profile

A

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
Q

Types of Error

A

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
Q

Signal-To-Noise Ratio

A

Should be as high as possible (Signal/Noise)

40
Q

Sources of Noise

A

Power-line frequency noise or interference (very common; picked up in long lead lines)
Electromagnetic
Electrostatic interference from other devices
Leakage current

41
Q

Stability

A

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
Q

Isolation

A

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
Q

Simplicity

A

Reduce change for component of human error

Simple Reference Device- transducers calibrated at the factory

44
Q

Electrodes

A

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
Q

Transducer

A

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
Q

Electrode Problems

A 
High impedence (resistance) of human skin
10 k ohms (damp) to 500 k ohms (dry)

Movement artifact- slippage of electrode

47
Q

Types of Pressure Transducers

A

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
Q

Fluid Filled Systems Must Be…

A

Zeroed- reference baseline value
Leveled- Equalize catheter tip and transducer; use phlebostatic axis (4th ICS)
Calibrated- precalibrated when manufactured)

49
Q

Components in Fluid Filled P Monitoring System

A 
Transducer (electromechanical value)
Pressure tubing
Pressure bag (pump to higher P than patient)
Crystalloid
Amplifier
Oscilloscope/Monitor
50
Q

Strain Gauge

A

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
Q

Piezoresistivity

A

describes the changing resistivity of a semiconductor due to applied mechanical stress

52
Q

Types of Strain Gauges

A

Unbonded- linear over large range of inputs, delicate

Bonded (we see these)- rugged, small linear range of inputs

53
Q

Wheatstone Bridge

A

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
Q

Pressure Wave Signal Path

A

Pressure wave, transducer, strain gauge changes R, wheatstone bridge, monitor signal

55
Q

Artifact

A

false signals superimposed on true signal

56
Q

Calibration

A

standardization of measuring instrument: the checking of a measuring instrument against an accurate standard to determine any deviation and correct for errors

57
Q

Catheter Whip

A

movement of catheter tip within the blood vessel in response to pulsatile flow

58
Q

Damping

A

loss of energy and vibrations within the monitoring system

59
Q

Dynamic Response

A

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
Q

Fidelity

A

indication of system’s capacity to faithfully reproduce the physiologic event

61
Q

Natural Frequency

A

frequency at which the system vibrates when stimulated by pulsatile signals

62
Q

Overshoot/Undershoot

A

system vibration that occurs when the patient’s pressure wave contains a component frequency equal to the system natural frequency

63
Q

Ringing

A

multiple small spikes on the waveform due to inadequate dynamic response characteristics

64
Q

Cardiovascular System: 3 types of pressure

A

Hemodynamic
Kinetic energy
Hydrostatic

65
Q

6 Physical Principles

A

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
Q

Hydrodynamic Pressure

A

pressure exerted by fluid in motion

67
Q

Natural Frequency

A

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
Q

Underdamping

A

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
Q

Overdamping

A

component frequency exceeds frequency response of the system; portions of waveform dependent on those frequencies will be blunted and obscured

70
Q

Resonance

A

the tendency of a system to oscillate at a greater amplitude at some frequencies than at others

71
Q

System Characteristics to Reproduce Waveforms

A

Amplitude linearity
Adequate bandwidth
Phase linearity

72
Q

System Characters you DO NOT want to Reproduce Waveforms

A 
Phase Distortion (phase shift)
Underdamping
Overdamping
Resonance
Catheter Whip

Monitoring of CV Patient I (4 decks)

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