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Physiology - Hayley > Instrumentation 2 > Flashcards

Instrumentation 2 Flashcards

1
Q

What do ADCs do

A

Convert continuous analog signal to digital signal

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2
Q

Describe the process of sampling

A

Digitising analogue signals into a series of discrete scales/readings

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3
Q

What is sampling time

A

The time between each sample/reading when you are converting analogue to digital signal

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4
Q

When converting analogue to digital signal, what would be the change to the amount of information you have/accuracy of the conversion if the sampling time was small

A

If the sampling time is small this means that when converting to digital, you are taking lots of samples (you will have more information/curve will be more accurate).

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5
Q

What is the equation for sampling frequency

A

Fs = 1/sampling time (Ts)

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6
Q

Digital signals have a minimum voltage change they can detect - true or false

A

True - digital signals have finite resolution (unlike continuous signals which have an infinite range).

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7
Q

What number system does digital system use

A

Binary

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8
Q

What is the equation for how many voltage steps a ADC can detect

A

N = 2^M

N - number of voltage steps a ADC can detect
M = number of bits in the ADC

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9
Q

How do you know how many bits are in a digital wave

A

By looking at the numbers on the Y axis and seeing how many values there are (i.e 10 = 2, 100 = 3)

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10
Q

What is the equation for the minimum voltage change an ADC can convert

A

ΔV = Vref / N

V ref - maximum voltage change the ADC can measure
N = number of voltage steps the ADC can detect

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11
Q

What is V ref in regards to ADC

A

maximum voltage change the ADC can detect

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12
Q

How do you find the V ref when looking at a ADC wave graph

A

This will be the highest number on the Y axis

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13
Q

What two things is the accuracy of the ADC dependant on

A

Sample frequency and resolution (number of bits)

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14
Q

What must the sampling rate be of ADC in order to capture all the frequencies in the wave

A

The sampling rate must be 2 times larger then the largest frequency in the wave

Fs > 2B

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15
Q

What does it mean for a signal to be ‘completely determined’ in ADC

A

A signal can be classified ‘completely determined’ is there is no frequencies in the signal that are higher then the bandwidth of the signal (B)

This doesn’t mean that the samples alone are the full signal, it means that we can get the full signal back from the conversion if we need too (because we haven’t lost any frequencies).

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16
Q

What must the ADC sampling rate be is the analogue maximum frequency is 500Hz

A

Sampling rate must at least be 1000Hz

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17
Q

How can analogue filters be used to help in ADC

A

They can be used before digitisation to ensure the input analogue signal doesn’t contain frequencies above the Nyquist limit (if there were signals above the Nyquist limit then these wouldn’t be able to be digitalised by the ADC)

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18
Q

When are digital filters used in a circuit

A

These are used after an analogue signal is digitised to remove any irrelevant parts of the signal

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19
Q

What is the usual pass band of a filter used in ECG

A

150Hz

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20
Q

What is the ideal frequency response for a unity gain buffer

A

Gain of 1 or 0dB

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21
Q

What is the corner frequency

A

This is the point when the attenuation of a signal is 3dB

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22
Q

Explain how you would draw a high pass filter

A

Axis: Y axis Gain, X aixs Frequency (Hz)

The ‘stop band’ will begin at low numbers, have a transition period beginning with the ‘transition band’ then will plateau off creating the ‘pass band’ at higher numbers after the ‘corner frequency’

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23
Q

Explain how you would draw a low pass filter

A

Axis: Y axis Gain , X aixs Frequency (Hz)

The ‘pass band’ will begin at high numbers, have a transition period beginning with the ‘corner frequency’ then will plateau off creating the ‘stop band’ at lower numbers after the ‘stop band’

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24
Q

Explain how you would draw a band pass filter

A

This will look like a mountain

Axis: y axis = Gain. X axis = frequency (Hz)

The ‘pass band’ will be at the peak of the mountain.

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25
Q

Explain how you would draw a notch filter

A

This will look like a deep crypt

Axis: y axis = Gain. x axis = frequency (Hz)

The stop band will be at the opening of the crypt. Frequencies on either side of the stop band will be able to pass through the filter

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26
Q

What sort of filter is used in power supplies to remove the 50Hz AC frequency

A

Notch filter

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27
Q

What many coefficients/taps does the FIR filter have

A

n+1

e.g 5th order FIR has 6 taps/coefficents

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28
Q

How is the output calculated in FIR filters

A

Multiplying the latest and n previous values of the input signal

e.g for a 4th order FIR filter: you multiply the most previous input by the 4 most previous inputs (5 number multiplying in total)

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29
Q

How is the output calculated in a IIR filter

A

multiplying the latest and n previous values of the input signal (same as FIR) AND multiplying the n precious values by their corresponding coefficient

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30
Q

What filters, FIR or IIR contains feedback loops and what can this result in the stability of the filter

A

IIR contains feedback loops and this can result in it being unstable if it is not designed properly

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31
Q

How many inputs and outputs does a IIR filter have

A

n + 1 input coefficent
n output coefficents

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32
Q

If you put a single 1 surrounded by zeros into a FIR and IIR filter respectively, what would be the output

A

FIR - the output would be finite (usually 0)

IIR - output would be infinate due to feedback

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33
Q

What is phase response in a filter

A

The amount by which a signal component of different frequencies are shifted in phase at the output of the filter, compared to the input

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34
Q

Why is phase delay not ideal

A

Differing phase responses at different frequencies can distort the signal

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35
Q

What is the ideal shape of the phase delay in a filter

A

Linear - this will mean all frequency components are shifted in time by the same amount such that the relationship that existed across frequencies at the input of the filter remain the same at the output

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36
Q

What filter, FIR or IIR has a linear phase response

A

FIR

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37
Q

What is the group delay of a filter and where on the filter graph is this found

A

This is the slope of the phase response (steepness of the line) and this corresponds to the absolute time delay of the signal thorugh the filter

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38
Q

What will the phase delay be on FIR filters that have symmetric coefficients

A

Phase delay will be linear

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39
Q

What is pass band ripple

A

The measure of how flat the amplitude of the frequency response is in the pass band of the filter

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40
Q

FIR filters with symmetric coefficients have what type of group delay

A

Constant group delay

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41
Q

What is the equation for group delay in FIR filter

A

FIR group delay = (n taps - 1) / 2fs

Fs = sampling frequency

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42
Q

What Law/Equations covers the basics of fluid dynamics

A

Ohms law

P = QR

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43
Q

What two factors is blood flow in the arteries dependant on

A

The energy needed to drive the blood
The resistance to the flow present

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44
Q

A rise in blood flow is defined by what three energies

A

Pressure energy
Kinetic energy
Gravitational energy

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45
Q

What is the relative velocities of laminar and turbulent flow

A

Laminar flow - consistent
Turbulent flow - fluctuations in velocity

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46
Q

In regards to the Reynolds number, when does laminar flow occur

A

Laminar flow occurs when the velocity is below the Reynolds number

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47
Q

What is the Reynolds number and how is it calculated

A

Predicts the flow patterns under different conditions

Re = inertia/viscious

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48
Q

What is the equations for flow

A

F = velocity x cross-sectional area

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49
Q

What are Newtonian fluids

A

Newtonian fluids are a category of fluids that have a constant viscosity regardless of the shear rate or the force applied to them.

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50
Q

What law do Newtonian fluids follow

A

Newtons Law of viscocity

τ=η⋅ (dy/du)
​
T = shear stress applied to the fluid
n = viscosity of fluid
du/dy = shear rate

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51
Q

What is the result on the flow and viscosity of a Newtonian fluid when it is subjected to different forces/stresses

A

This means their flow behavior or viscosity does not change when subjected to different forces or stresses.

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52
Q

What does the Youngs Modulus explain

A

The ratio between stress and strain used to express the elasticity of a fluid

(how easily can a fluid stretch and compress)

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53
Q

What is the equation for Youngs Modulus

A

E= σ/ϵ

𝐸= Young’s modulus,
σ is stress,
ϵ is strain.

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54
Q

What is shear stress

A

Forces that act parallel to the surface of the material

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55
Q

What is shear strain

A

force acting on material when subjected to movement

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56
Q

In non-Newtonian fluids what occurs to the viscosity when it experiences shear stress and strain

A

Viscocity changes (unlike Newtonian fluids)

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57
Q

What type of fluid is blood

A

Pseudoplastic

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58
Q

What would be the relathionship of shear stress and shear rate of an ideal fluid

A

Shear stress and shear rate would be directly proportional (linear)

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59
Q

What is a pseudoplastic fluid

A

A pseudoplastic fluid is a type of non-Newtonian fluid characterized by a decrease in viscosity as the shear rate increases.

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60
Q

What is a dilatant fluid

A

A dilatant fluid is a type of non-Newtonian fluid characterized by an increase in viscosity as the shear rate increases.

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61
Q

What are the four characteristics of an ideal fluid

A

Zero viscosity
Incompressible
Infinite bulk modulus
No surface tension

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62
Q

What is the equation for velocity under pulsatile flow

A

c = √Eh/pd

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63
Q

What does LaPlace wall tension tell us

A

The pressure applied onto the wall is directly proportional to the tensional stress and inversely proportional to the radius of the wall

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64
Q

According to LaPlace wall tension, how much pressure can be applied to small vessels

A

A lot - the smaller the vessel, the larger the pressure that can be applied to it

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65
Q

What is critical radius of arteries

A

This is the point at which arteries have expanded so much that they become unstable

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66
Q

How would you estimate the critical radius of an artery

A

The critical radius is usually 2 times the original internal diameter of the artery

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67
Q

How foes flow spilt when it gets to a bifurcation

A

Q = Q1 + Q2

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68
Q

What two forces does flow experience when it flows along a bend

A

Viscous force
Centrifugal force

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69
Q

What does Bernoulli equation tell us

A

The equation states that the total mechanical energy of the fluid remains constant if the flow is steady and frictionless (non-viscous)

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70
Q

What 5 things must we assume for Bernoulli’s equation to be applicable

A

Flow must be stead
Fluid my be incompressible
Viscosity must be negligible
Flow must be uniform
Flow must be irrotational

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71
Q

What law explains the flow incompressible and Newtonian fluids (laminar flow)

A

Poiseuille’s equation

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72
Q

What are the two forces involved in the elastic recoil of the lung

A

Tissue forces from stretching (elastic elements)

Surface forces (surface tension)

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73
Q

What is transpulmonary pressure

A

The difference between the pressure inside the lung (alveolar pressure) and the pressure outside the lung (pleural pressure)

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74
Q

What is elastance

A

The resistance to change in shape when mechnical load is applied

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75
Q

What law describes movement of gas in the respiratory system

A

Ficks Law of diffusion

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76
Q

What is the equations for Ficks Law of diffusion

A

V = DAP/T

V = volume of gas
D = diffusion cooefficent
A - surface area
P = pressure gradient
T = thickness of barrier

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77
Q

What are some factors that affect diffusion of gas

A

Area of membrane
Thickness of membrane
Solubility of gas
Molecular weight of gas
Pressure difference

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78
Q

What are the two factors that make an ideal gas

A

Does not attract or repel each other

Takes up no space (has no volume)

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79
Q

How many gases are ideal gases

A

No gas is truly ideal

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80
Q

What equation can we use to provide a good approximation of real gas behaviour

A

PV = nRT

n = number of moles
R = universal gas constant
T = temperature in kelvins

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81
Q

Avogadro’s Law describes what

A

Equal volumes of gases at the same temperature and pressure contain the same number of molecules

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82
Q

What does Boyles Law state

A

The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to its volume

P = 1/V

83
Q

What does Charls Law state

A

At a constant pressure, the volume is directly proportional to temperature

84
Q

What does Gay-Lussacs Law state

A

For a constant volume, the pressure is directly proportional to the temperature

85
Q

What Law describes why respiratory volume values change in regard to room temperature

A

Charls Law

86
Q

What does Daltons Law state

A

Total pressure of a gas is the sum of the individuals pressure of all the gas molecules in the container

87
Q

What are the three ideal gas laws

A

Boyles Law
Charls Law
Gay-Lussacs Law

88
Q

What two characteristics are the best to reveal the operational condition of the respiratory system

A

Flow rate and Pressure

89
Q

What is the best way to measure the pressure difference in the respiratory system

A

Using a differential pressure sensor

90
Q

How does the use of an oxygen mask relate to ohms law

A

By accelerating oxygen through a small nozzel, causing a drop in pressure that allows air to be draw in and mixed with oxygen in the body

91
Q

When in a circuit are analogue filters used

A

These are used before ADC

92
Q

What does a high pass analogue filter remove

A

These remove any offset and large slow drifting components of the signal (often referred to as a DC offset filter)

93
Q

What do low pass analogue filters remove

A

Remove high frequencies and allow the analogue signal to meet the Nyquist sampling theorem (often referred to as an anti-aliasing filter)

94
Q

What frequency, high or low, is able to pass through a capacitor like a wire

A

High frequency

95
Q

What frequency, high or low, will not be able to pass through a capacitor and why

A

Low frequency - capaictors have high impendance/resistance to low frequency signals

96
Q

What is the effect of low frequency signals when a capacitor is present

A

A capacitor will block low frequency signals

97
Q

What is the corner frequency in regards to capacitors

A

This is where the resistance of the capacitor become relevant (the frequency of the wave is now at an appropriate value that is will begin to charge the capacitor)

98
Q

Explain the basic layout of the low pass analogue filter using resistor and capacitor.

How does this differ in a high pass analogue filter

A

Resistor would be in-between Vin and Vout. Capacitor will be on a branch off this wire.

In a high pass filter, the C and R will be swapped

99
Q

What is the role off of a single stage analogue filter

A

20dB per decade

100
Q

What is a decade in the terms of analoug filters

A

A decade occurs when the frequency is multiplied by 10

101
Q

What are higher order analoug filters

A

Filters that have more than one filter present

102
Q

What type of filter has the flattest group delay

A

Bessel filter

103
Q

What filter has the steepest role off and what is sacrificed in this filter to allow this

A

Chebyshev filter - these can have large levels of distortion

104
Q

What filter attempts to have the best of both role off and group delay

A

Butterworth filter

105
Q

Why can you not just put one filter after another in a circuit when making a higher order filter

A

Putting them one after another will affect the impedance of the components before it

106
Q

How can we have multiple filters in one circuit without affecting the impedance

A

Unity gain buffers can be used

107
Q

In higher order filters that contain unity gain buffers, what other electrical components do they contain

A

They will have a resistor and capacitor in between each unity gain buffer.

108
Q

What is the difference between active and passive analoug filters

A

Active filters require op amps
Passive filters require inductors

109
Q

What is the signal chain in machinery

A

Physical stimulus
Sensor/Tranducer
Analoug Filter/Amp
ACD
Digital Processing
Display

110
Q

What equipment is especially prone to change in transfer fucntion over time

A

Mechanical sensors and actuators

111
Q

What are the two types of calibration

A

Measurement of an artificial signal source or test load

Measurement of a biological control

112
Q

What is the normal frequency of an ECG as seen on the rhythm strip

A

0.15-150Hz

113
Q

What sort of amplifiers are used in EEG

A

Differential amps

114
Q

Concentric EEG recording needle
- Where is the reference active electrode located in the needel
- What degree of field does it have

A

Reference electrode on cannula, active electrode inside needle

180 degree field

115
Q

Monopolar EEG recording needle
- Where is the reference active electrode located in the needel
- What degree of field does it have

A

Active electrode inside needle, reference electrode external

360 degree field

116
Q

Bipolar EEG recording needle
- Where is the reference active electrode located in the needel

A

Active and reference electrode in needle

117
Q

What is Laplacian Montage

A

Measures potential of all the neighbouring electrodes around it and averages them

118
Q

What is the filter bandwidth setting of an EEG usually

A

0.5-70Hz

119
Q

What is the sampling rate in EEG usually

A

500

120
Q

What is Amplitude Integrated EEG

A

This is a compressed display of a single pair of electrodes to monitor brain activity over long periods of time

121
Q

What sort of electrical activity are we measuring in motor nerve conduction studies

A

Compound action potentials

122
Q

Explain the basics of performing a motor nerve conduction study

A

Surface electrodes are placed on the muscle that we are stimulating

Stimulating TWO points (e.g elbow and wrist)

123
Q

What direction is the cathode facing in motor nerve conduction studies (black)

A

Cathode (black) facing the surface electrodes (black to black)

124
Q

Where are the recording electrodes put when conducting a sensory motor nerve conduction study

A

Recording electrodes put on two points of one finger (black one closest to palm)

125
Q

Explain the flow of ion in cathodal stimulation during nerve conduction studies

A

In cathodal stimulation, anions (-) are discharged into the body as current flows from the cathode (-) through the tissue, and back to the anode (+)

126
Q

Explain the flow of ion in anodal stimulation during nerve conduction studies

A

In anodal stimulation, cations (+) are discharged into the body as current flows from the anode (+), through the tissue, and back to the cathode (-)

127
Q

What is the definition of latency in regards to nerve conduction studies

A

The duration between a stimulating point and where the response is detected by the recording electrode

128
Q

Why must an evoked potential be extracted using signal averaging

A

Because evoked potentials are of very low amplitude

129
Q

What are evoked potentials

A

Electrical manifestation of the brains response to an external source

130
Q

What is signal averaging

A

A signal processing technique aimed to increase strength of a signal relative to noise

131
Q

What three factors must there be for signal averaging to work

A

Signal must be repetitive
Noise must be random
Temporal position of signal must be known

132
Q

What is the aim of signal averaging

A

To increase to signal to noise ratio (higher the better)

133
Q

What are visual evoked potential studies used for

A

Used to investigate the integrity and function of the optic nerve

134
Q

What are the two types of stimuli used in visual evoked potential studies

A
  1. Pattern reversal (elicits stimuli through rapid change in a given pattern)
  2. Flash stimulation
135
Q

What method is used when placing electrodes for visual evoke potential studies

A

Queen Square Method

136
Q

How many sweeps is used in visual potential studies

A

100-200

137
Q

What does somatosensory evoked potential studies allow us to analyse

A

How the electrical potential travel through the somatosensory nerve via the spinal cord

138
Q

How many sweeps is used in somatosensory evoked potential studies

A

700-1200

139
Q

What are brain auditory evoked potential studies used to analyse

A

Acoustic neuromas

140
Q

How many sweeps are used in brain auditory potential studies

A

1800-2000

141
Q

What is quantitative sensory testing

A

Standardised non-invasive test designed to diagnose small fibre neuropathy

142
Q

What three methods of quantitative sensory testing are used

A

Thermal threshold, pressure sensor, vibration

143
Q

What do sudomotor function exams measure

A

The nerve that control sweating

144
Q

What sort of pathophysiology can sudomotor function tests help us diagnose

A

Autonomic nervous system disorders, peripheral neuropathies, pain disorders

145
Q

What is measured in sudomotor function exams

A

Electrochemical skin conductance (ECS)

146
Q

What is magnetoencephalography

A

Maps the function of the brain via magnetic fields produced by the brain

147
Q

The amplitude and dynamic behaviour of manometry recordings is dependant on what 3 things

A

Luminal contents
Degree of closure of distal sections of the lumen
Rate of contractions of the luminal wall

148
Q

How does a air monometer measure changes in pressure

A

Changes in pressure inside the balloon once inflated allows a direct measure of luminal activity

149
Q

What type of GI catheter uses MEMS system

A

Solid state catheter

150
Q

What are two limitations of solid state manometers

A

Prone to baseline drift and sensor drop out

151
Q

How does fibre optic catheters measure pressure

A

mechanical system that blocks the light as pressure decreases and can detect how much light has been blocked)

152
Q

What GI catheters are best used to reach long and hard to get areas of the GI tract

A

Fibre-optic manometers

153
Q

What is the role of impedance monitoring

A

Monitor luminal contents in the oesophogus

154
Q

Where are the electrodes located on the catheter used for impedance monitoring

A

Located on the outer surface of the catheter so they can contact to the luminal wall/luminal contents

155
Q

What is the relative difference in electrical activity of a bolus in relation to the mucosal wall of the GI tract

A

The bolus has more electrical activity compared to the mucosal wall

156
Q

Impedance Monitoring GI can detect non-acidic reflux events, true or false

A

True

157
Q

A pH of what in a pH GI test indicated reflux from the stomach

A

~4

158
Q

What are barsostat studies used for in GI

A

Used to investigate sensory ano-rectal disorders

159
Q

What are 3 emerging technologies in GI

A

Motility tracking systems - magnetic pill swallowed and makes 3D map of GI tract

Small bowel high resoolution monometry

Functional Luminal Imaging Probe (FLIP)

160
Q

What is the Power Supply Rejection Ratio (PSRR)

A

How well a circuit is able to supress vaiations in the power supply so that it doesnt effect the circuits performance

161
Q

What is Common Mode rejection (CMRR)

A

The amplifiyers abilityto reject amplyfying signals that are common in both signals and only amplyfying the desired differential signal

162
Q

Signal to noise ratio
- What is it
- What is the ideal SNR

A

The level of a desired signal to the level of background noise

Ratio higher than 1:! indicates more signal than noise (bigger the better)

163
Q

In what environment are differential amplifiers good in and how does it achieve this

A

Good in noisy environments - it filters out noise by working on the principle that the unwanted electrical noise couples equally on both input terminals of the amplifier so therefore be rejected

164
Q

What are capacitors good a filtering

A

They remove low frequency’s and noise and block DC signals and allow only high freuqnecy signals such as AC signals to pass through

165
Q

What is the difference between an inverting and non-inverting amplifier

A

Inverting - Ground is connected to the + input
Non-inverting - Ground is connected to the - input

166
Q

What is offset voltage

A

The very small amount of difference between the 2 inputs in a op-amp that is present in real life situations

167
Q

What terminal is the negative feedback connected to in an op-amp

A

negative

168
Q

What is the ideal difference between the + and - input terminals in an op-amp

A

0

169
Q

What are the 3 main components of an op amp

A

Infinite gain
Infinite input impedance (no current)
Infinite output voltage

170
Q

When a capacitor and resistor are in parallel, what is their relationship to voltage

A

They must always have the same voltage

171
Q

What is the effect of Vout is the capacitance of a capacitor increase

A

V out deceases because the capacitor is eating more of its charge

172
Q

What happens to the decibel calculation when the circuit attenuates a voltage

A

It becomes negative

173
Q

What is gain dependant on

A

the frequency at which it was measured

174
Q

What is the SI unit for inductance

A

L - henreys

175
Q

How does a capacitor filter

A

By using the stored charge it is able to release voltage during the negative deflection of the AC wave, thus filtering out the drops in voltage

176
Q

Where in the clinical setting are capacitive sensors/transducers used

A

Intracranial pressure monitoring/intraocular pressure measurements

177
Q

What 3 things can be used to measure the uterine fundus in 2nd and 3rd trimester

A

Tape measure
Obsetric Calipers
Palvimerter

178
Q

At what age gestation is a heart beat developed and at what age gestation can you hear it through transabdominal fetoscope

A

Heart beat developed ~41 days

You can hear it ~18 weeks

179
Q

What are 3 artefacts that make foetal ECG difficult

A

Maternal heart beat
Foetal movement
Maternal movement

180
Q

What equipment is able to detect the foetal heartbeat at ~10-12 weeks

A

Ultrasonic doppler

181
Q

What is foetal carrdiotocography (CTG)

A

Ultrasound real time recordings of the foetal heart rate and uterine activity

182
Q

What are the indirect and direct methods of foetal cardiotocography (CTG)

A

Indirect - sensors places on the maternal abdomen

Direct - sensors places on the foetus and within the uterine cavity

183
Q

What change in heart rate during active labour is a sign of foetal wellbeing

A

An increase in heart rate from baseline

184
Q

What is a common change in foetal heart rate during a contraction

A

Abrupt decrease in heart rate from baseline

185
Q

What changes in foetal heart rate may indicate foetal distress

A

When the heart rate returns to baseline after the contractions end

186
Q

What is the direct method of foetal electrocardiogram

A

Biopotential electrodes are places through the cervix on the foetal presenting part during labour (usually the head)

187
Q

What part of the foetal ECG are difficult to detect, and how do we use this to calculate foetal heart rate

A

Only the R waves can be detected as the rest of the ECG components are buried in noise
Heart rate is calculated by 6000/R-R interval (mm / min)

188
Q

What is the indirect method of measuring foetal ECG

A

Using doppler ultrasound - these usually detect the pulsatile movement of RBCs and/or opening and closing of the valves

189
Q

What are some major differences between adults and neonates that we must consider when treating them

A

Size
Mobility
Ability to communicate
Anxiety factors
Body proportions
Different physiological functions

190
Q

What are 5 limitations/challenges of working in the NICU/with neonates

A
  1. Heat produced from equipment is more likley to damage their skin
  2. Sentivie skin
  3. Electrodes producing pressure sores
  4. Prone to infection - must be more vigilent with disinfecting devices
  5. Warm environment makes it difficult to maintain impedance levels
191
Q

What are 4 limitations to working in the warm environment of the NICU in regards to maintaining device impedance

A
  1. Increase skin moisture can reduce impedance
  2. Fluctuating temperature in the NICU can effect skin temperature/blood flow which can effect impedance
  3. Adhesives on electrodes may not stick as well in warm/humid conditions
  4. Device sensitivity to noise - ICE contains lots of devices such as incubators, humidifiers that create a lot of electrical noise
192
Q

What is used to measure growth (height and weight) of infants/neonates

A

Stadiometer

193
Q

How is babies breathing pattern measured at home

A

Apnoea machine using thoracic impedance

194
Q

How do electrodes differ for neonates compared to adults

A
  1. Electrodes are smaller
  2. Adhesive and electrolyte paste are less irritating (weaker adhesive and low Cl-)
  3. Signal processing takes into account the normal high heart rates of neonates
195
Q

What type of apneoa does transthoracic impedance monitoring in infants measures

A

Central apneoa only

196
Q

How is blood pressure usually measured in NICU

A

Direct catheter put into the umbilical arteries

197
Q

What are the two methods that blood gas monitoring can happening in neonates

A
  1. Drawing arterial/venous blood samples and analysing them in a blood gas analyser
  2. Continuous blood gas monitoring - catheter with electrochemical or optical sensors continuously analyses blood gases
198
Q

What is PO₂ amperometry

A

technique used for measuring the partial pressure of oxygen in a gas or liquid phase.

199
Q

How is PO2 Amperometry measured

A

Blood diffuses through an O2 permeable membrane - the greater the O2, the greater partial pressure, the higher the requirement for electrons to reduce it. The current at the cathode is directly related to the partial pressure of oxygen in the solution

200
Q

how is blood pH measured in neonates

A

Measured directly from the tip of a catheter. Electrochemical sensor makes a poteniometric measurements

201
Q

How is PCO2 measured in neonates

A

Measured electrochemically sensing the change in H+ as this is proportionate to the concentration of PCO2

202
Q

Why is continuous EEG monitoring of neonates particularly important

A

Risk of seizures is greatest in the first 3 days of life - seizures in neonates are very subtle and cannot always be seen without an EEG

203
Q

What type of EEG is used in the NICU and why

A

Amplitude Integrated EEG
- Only requires 1 pair of electrodes
High amplitude (for the smaller brain waves)

204
Q
A

Physiology - Hayley (9 decks)

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