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Physiological Measurement Flashcards

0
Q

Define accuracy

A

Degree to which measurements of a variable have a consistent error in one particular direction away from true value.

Degree if closeness to quantity’s actual value

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1
Q

Define precision

A

How reproducible the results are. Clustering

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2
Q

What is diagnostic accuracy?

A

Measure of reproducibility, sensitivity, specificity, predictive value, measurement complexity.

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3
Q

What is sensitivity?

A

[TP/all with disease (tp +fn) ] x 100

Test +’ve - likelihood the test is correct. High sensitivity - high proportion of people with disease will be detected

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4
Q

What is specificity?

A

[ TN/all without disease (TN + FP)] x100

True -‘ve rate. Likelihood that the test is actually negative

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5
Q

What is the normal hearing range for a human adult?

A

20-20,000 Hz

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6
Q

What the different types of hearing loss?

A

Neural dysfunction - disruption to neural pathway/cortex, acoustic neuroma, psychogenic.
Conductive deafness - quiet but not distorted. Responds to amplification
Sensory-neural - quiet and distorted. Not to amplification
Mixed

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7
Q

What can you examine when viewing with an otoscope?

A

Outer ear, middle ear and ear canal

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8
Q

What ear examinations are subjective?

A

Weber test, rinne test, pure tone audio gram, speech audiometry, paediatric audiometry

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9
Q

Which ear examinations are objective?

A

Tympanometry, otoacoustic emissions, electrocochleography, auditory brain stem response, cortical evoked responses.

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10
Q

What does the Weber test show?

A

Midline structure -> localises to one side of the head. Must place on bone.
Equal - bilateral hearing loss or normal hearing.
Conductive loss- localises to ear which is loudest - bone conduction
Sensory-neural loss- quieter in affected ear

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11
Q

How is the Rinne test performed?

A

Hold tuning fork in front of and behind the ear (mastoid process). Air conduction should be louder.
+ve= air conduction louder
-ve= bone conduction louder

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12
Q

What are the advantages of a tuning fork assessment?

A

Simple

Minimal equipment

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13
Q

What are the disadvantages of the tuning fork test?

A

Doesn’t quantify degree of hearing loss
Influenced by technique
Quiet test environment
Taping of ear not being tested

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14
Q

What sort of test is a tuning fork assessment?

A

Psychophysical - tests whole auditory pathway

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15
Q

What sort of assessment is pure tone audiogram?

A

Psychophysical

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16
Q

What are you testing for in pure tone audiography?

A 
Sensitivity to pure sounds. 
Equipment standardised by British society of audiology. 
0 = normal. 
-ve = better than normal
\+ve = worse than normal
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17
Q

What are the advantages of a pure tone audiogram?

A

Quantitative measure
Standardised
Differentiate between causes

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18
Q

What are the disadvantages of a pure tone audiogram?

A

High level of patient cooperation
Influenced by technique, environment, equipment and taping of ear.
Learning effects
Not in young or elderly, learning difficulties

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19
Q

What sort of hearing test is speech audiometry?

A

Psychophysical

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20
Q

Explain speech audiometry

A

Pre recorded speech material at different intensities consisting of 3 phonemes

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21
Q

What are the advantages of speech audiometry?

A

Physiologically relevant
Differentiate between losses
Help rehabilitation

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22
Q

What the limitations if speech audiometry?

A

Speech not in all languages
Degree of cooperation
Not in young or limited understanding

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23
Q

What sort of test is paediatric audiometry?

A

Psychophysical

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24
Q

What are the different hearing tests for varying paediatric ages?

A

6-18 months - distraction testing
18-30 - cooperation testing - visual reinforcement
30+ - performance testing

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25
Q

What are the sources of error in paediatric audiometry?

A 
Visual cueing 
Auditory cueing
Distractor technique
Tactile cueing
Olfactory cueing
Rhythmic stimulation
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26
Q

What can be viewed by tympanometry?

A

Outer ear, ear canal and middle ear

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27
Q

How do you perform tympanometry?

A

Measure of tympanic membrane integrity. Pure tone played into ear canal, intensity monitored whilst static pressure is applied. Results expressed as compliance

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28
Q

What are the advantages of tympanometry?

A

Simple and quick

Minimal cooperation

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29
Q

What are the disadvantages of tympanometry?

A

Airtight sealed required

Not measure of hearing

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30
Q

What are the different types of otoacoustic emissions?

A

SOAE - spontaneous otoacoustic emissions
TEOAE - transient evoked otoacoustic emissions
DPOAE - distortion product otoacoustic emission

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31
Q

What are you testing for using otoacoustic emissions?

A

Outer hair cells of the cochlea

Comparison between the frequency content of the stimulus and emission determines integrity.

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32
Q

What are the advantages of otoacoustic emissions?

A

Non-invasive
Quick, minimal patient cooperation
All ages
Reliable

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33
Q

What are the disadvantages of otoacoustic emissions?

A

Not measure perception
Results don’t quantify cochlear sensitivity
Responses abolished with hearing losses above 30-40dB

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34
Q

Which sections of the hearing pathway does electrocochleography examine?

A

Outer ear, ear canal, middle ear, cochlea outer hair cells, cochlea inner hair cells, vestibulocochlear nerve (CN VIII)

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35
Q

What does electrocochleography test for?

A

Functional integrity of the cochlea. Series of clicks and tones

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36
Q

What are the advantages of electrocochleography?

A

Objective
Response not affected by sleep, sedation or general anaesthesia
Intra-operative monitoring

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37
Q

What are the disadvantages of electrocochleography?

A

Not perception
Procedure in invasive
Normative data required for comparison
Below 1KHz not obtained reliably

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38
Q

What does auditory brain stem response test for?

A

Outer ear to -> brain stem
Electrical potential originating from auditory nerve/brain stem- evoked by stimulation of cochlea.

Procedure = objective. Needs minimal myogenic activity

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39
Q

What are the uses for auditory brainstem responses?

A

Screening of newborns hearing

Intra-operative monitoring

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40
Q

What are the advantages of auditory brainstem responses?

A

Objective
Not influenced by sleep, sedation, or general anaesthesia
Intra-operative monitoring

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41
Q

What are the disadvantages of auditory brainstem responses?

A

Small signal - interference
Relaxed, asleep
Not test of perception
No info beyond brainstem

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42
Q

What is cortical evoked responses (CERA) assessing?

A

Outer ear -> primary cortex
Evaluation of: - inconsistent or unreliable results
- unwilling to participate with subjective testing
- medico-legal cases with no organic cause

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43
Q

What are the advantages of cortical evoked responses?

A

Objective
Assessment of high auditory function
Absence of cortical/perceptual deficit, frequency specific threshold within 5-10dB of patients subjective threshold

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44
Q

What are the disadvantages of cortical evoked responses?

A 
Not test perception
Large degree of inter/intrasubject variability
Affected by patients alertness
Not suitable  for paediatrics
Time-extensive. Up to 1 hr
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45
Q

What can be detected on spirometry?

A

Excessive mucus secretion
narrowing of airways - asthma, inflammation or oedema
loss of radial traction - emphysema

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46
Q

When the pressure is large in the thorax, when do the airways collapse?

A

Expiration

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47
Q

what is the purpose of helium dilution?

A

measures volume of gas that is in communication with the airway opening. i.e. the vol. that is ventilated.

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48
Q

what is the calculation to figure out the volume after a helium dilution?

A

v1C1=V2C2

v1 - starting volume of spirometer
c1- starting concentration of helium
v2- final volume (lungs and spirometer)
c2 - final concentration of helium

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49
Q

what is measured on spirometry?

A

fvc - forced vital capacity

FEV1 - forced expiratory volume in 1 second

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50
Q

Explain a nitrogen washout

A
  • single breath to residual volume
  • max inspiration of pure oxygen
  • breath out regularly and slowly, record levels of N2 on expiration
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51
Q

what happens to the concentration of nitrogen exhaled in asthmatics?

A

increases

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52
Q

what happens to the concentration of nitrogen exhaled in ciliary dyskinesia?

A

decreases

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53
Q

what is detected on an induced sputum?

A

cells of inflammation.

hypertonic saline solution inhaled which induces coughing and sputum

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54
Q

What are predictive values for respiratory investigations based on?

A

height

values from literature

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55
Q

What are the two diodes involved in oximetry?

A

Red light and infrared

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56
Q

What are the limits for oximetry in an adult?

A

HR - 140/55

Sat - 100/85

57
Q

What are the limits for oximetry in a baby?

A

HR will be higher

Sat - 100/85

58
Q

Why might oxygen saturation be less than 100%?

A

Branchial veins drain directly into pulmonary vein

Varying types of Hb

59
Q

How to measure exercise induced asthma?

A

Measure FEV1 pre and post exercise

  • treadmill for 6 mins until optimum heart rate (target-80% of HR within first 3 mins)
  • looking for 15% change in FEV1
60
Q

What is investigated during plethysmography?

A

Changes in vol of organ or whole body

Measure thoracic gas vol and airway resistance.

61
Q

What is plethysmography good for?

A

Hyperinflation

62
Q

How is plethysmography carried out?

A

The pt sits in airtight cabin, breathe through pneumotachograph, a shutter will close the device occluding external airway-> fixed vol and temp

63
Q

What is the calculation for Functional residual capacity?

A

Resistance = pressure x flow

64
Q

What are the uses for chemical pathology?

A

Make diagnosis/confirm diagnosis
Monitor disease - routine biochemistry, tumour markers, hormone assays
Drug monitoring
Screening

65
Q

Define standard deviation

A

Square root of the variance and is a measure of the spread of distribution of values around the mean value.

The larger the spread the larger the standard deviation

66
Q

Define False positive rate

A

The proportion of tests which give a positive result who don’t have the condition

67
Q

Define true positive

A

Positive test result and actually have the condition

68
Q

Define true negative

A

Negative result and don’t have the condition

69
Q

Define false negative

A

Negative test result but does have the condition

70
Q

Prevalence value

A

True positive/(true positive + false positive) x 100

71
Q

What happens in obstructive jaundice?

A

Elevated ALP - bone, liver, intestine, placenta

72
Q

What happens in heptocellular jaundice?

A

Elevated ALT- liver

73
Q

What happens in mixed jaundice?

A

Both ALT and ALP are elevated

74
Q

What happens during a stress test when a patient has a growth hormone deficiency?

A

Infusion of insulin. Growth hormone and cortisol elevated.

Glucose must be below 2.2 for results to be effective

75
Q

What are the symptoms of hyperpituitarism?

A 
Visual field defects
Hypertension
Headache
Facial changes and fatal 
Increased growth hormone
76
Q

How do you calculate the ankle brachial pressure index (ABPI)?

A

KAnkle systolic/brachial systolic

Less than 1 = abnormal
Greater than 1 = normal

77
Q

What are the characteristics of ultrasound waves?

A

Loudness/amplitude
Frequency
Speed
Reflection - speculation at large surfaces. Scattering at small surfaces

78
Q

How does ultrasound work?

A

Uses a transducer with piezoelectric crystals -> change shape when a voltage is applied

79
Q

What characteristics does a flat linear probe have?

A

High frequency
High resolution
Poor penetration

80
Q

What characteristics does a domed transducer have?

A

Low frequency
Lower resolution
Greater penetration

81
Q

What is the brightness of an ultrasound image dependent on?

A

The intensity of the reflection

82
Q

What are the different types of Doppler?

A

Colour (duplex) - detects flow, gives crude direction of flow
B mode- black and white, greyscale
Spectral Doppler - direction, speed, quality of blood flow
Continuous wave Doppler - picks up all vessels at the same time

83
Q

Describe the 3 waves seen on a spectral Doppler?

A

Triphasic - normal in peripheral arteries
Biphasic- arterial stiffness
Monophasic - significant arterial disease. Renal and carotid arteries

84
Q

What is aliasing?

A

Speed of sampling is too slow so looks as if blood flow is moving backwards

85
Q

Explain the follow up to different sized abdominal aortic aneurysms?

A

<3cm = fine

3-5.5cm - 1% rupture risk

86
Q

Problems with venous disease?

A

Reflux - colour

Dvt - veins don’t collapse if clot present. In advanced diabetes, element of vein calcification

87
Q

Explain the difference in sizes of nerves

A

Motor - largest - myelinated
Sensory - thinly or not myelinated
Autonomic - smallest

Conduction velocity - faster in the largest

88
Q

What does an EMG machine record? (Electromyography)

A

Velocity and amplitude of action potential
Sensory nerve action potential (SNAP)
Compound motor action potential (CMAP)

89
Q

What is recorded from a motor neuron?

A

Start at 0mA and increase to 20/30mA

Record amplitude and duration

90
Q

What is recorded from a sensory neuron?

A

Purely sensory portion of nerve. Recording electrode must be proximal.
Amplitude less than motor
Duration - shorter than CMAP - measure of synchrony

91
Q

What are the limitations of an EMG machine?

A

Patient discomfort
Patient factors - movement, temp of limbs, peripheral oedema, inaccessible area, syncope
Equipment failure and interference
Over calling abnormalities

92
Q

How is muscle activity recorded?

A

Needle electrodes - local picture, intramuscular

Surface electrodes - general picture

93
Q

What are the myotomes?

A 
C1/c2 - neck flexion/extension
C3 - neck lateral flexion
C4- shoulder elevation
C5- shoulder abduction
C6- elbow flexion/wrist extension
C7- elbow extension/wrist flexion
C8-thumb extension
T1-finger abduction
L2- hip flexion
L3- knee extension
L4- ankle, dorsi flexion 
L5- big toe extension
S1- ankle plantar flexion
S2- knee flexion
94
Q

How can you interpret nerve damage?

A

Produce positive sharp waves.
Denervated fibres = 7-10 days
Sound produced by machine is related to the strength of the contraction.

95
Q

How can you interpret muscle damage?

A

Decreased duration of motor unit action potential

Decreased amplitude

96
Q

What are the limitations of EMG?

A

Technical interference, operator dependent,

Clinically invasive, risk of haematoma

97
Q

How is brain activity recorded?

A

EEG-electroencephalogram. Records electrical activity within brain.
Depth - dural or scalp.

Even numbers - right hand side. Odd numbers - left hand side. Z=midline.

98
Q

What are the normal wavelengths seen in brain activity?

A

Delta 13Hz

Montages - bipolar, referential, average.

99
Q

When is EEG used clinically?

A

Diagnosing epilepsy and localising site of seizure

Evoked potentials: visual evoked potentials
Somatosensory evoked potentials

100
Q

What are the advantages of evoked potentials?

A

Cheap, portable,non-harmful, excellent temporal resolution

101
Q

What are the disadvantages of evoked potentials?

A 
Poor spatial resolution, must be trained staff
Artefacts: biological 
                 Environmental 
                 Technical
                 Patient cooperation
102
Q

What are the stages of sleep?

A

Non REM - 4 stages, low frequency, high amplitude. Motor system capable
REM sleep - high frequency, low amplitude. Rapid eye movement, skeletal muscle paralysis. Muscle twitches.

103
Q

Name some disorders of initiating and maintaining sleep

A 
Insomnia
Depression
Paradoxical insomnia
Poor sleet hygiene
Drug induced
Fatal familial insomnia
104
Q

Explain a primary sleep disorder such as narcolepsy

A 
Excessive daytime sleepiness 
Hallucinations >10 mins
Sleep paralysis 
Disturbed night sleeping 
Cataplexy
105
Q

Explain a secondary sleep disorder such as obstructive sleep apnoea

A

Apnoea -100% for 10 secs
Hypopnoea - 50% decrease over 10 secs
Apnoea:hypopnoea index mild=5-14
Moderate =15-29
Severe = >30

106
Q

What are parasomnias?

A

Abnormal sleep behaviour and movements

107
Q

How is sleep assessed?

A

Diary
Actigraphy- detection of movement
Polysomnography - gold standard but expensive

108
Q

How is wakefulness assessed?

A

Questionnaires - epworth sleepiness scale (likelihood of falling asleep in 8 common situations)
Stamford sleepiness scale - 1=awake 8=asleep
Multiple sleep latency
Maintenance of wakefulness
Vigilance testing

109
Q

Why are radiological images used?

A

To “look inside” the patient
To confirm a diagnosis and or rule out a condition
Because the patient expects it

110
Q

Explain probability.

A

0- impossible
1- absolutely certain

P(a) = probability that a is true
P(a') = probability a is false
P(a|b) = probability a  is true given that b is true
P(a'|b) = probably that a isn't true given that b is true
111
Q

Explain Bayes’ Theorem

A

A way to update probabilities based on new evidence.
New odds ratio = old odds ratio x likelihood ratio

P(H|E)/[1-P(H|E)] = P(H)/[1-P(H)] x P(E|H)/P(E|H’)

112
Q

In ultrasound the spacial detail available depends on frequency, explain

A

High frequency - higher resolution
Low frequency - better depth penetration

Doppler - shift in sound frequency indicates motion. Common application to measure blood flow

113
Q

What are the different types of nuclear medicine?

A

Scintigraphy: produces plain 2D picture. Iodine scan for hypo/hyperthyroidism

Single photon emission computed tomography (SPECT): 3D picture produced. Gamma ray emitting radiopharmaceutical

114
Q

Explain the basis of positron emission tomography (PET)

A

Uses beta-particle emitting pharmaceutical

Beta particle decays to emit an electron and positron. 3D picture produced - fluoro-deoxy glucose

115
Q

What does x-ray absorption depend on:

A

Tube voltage - potential difference between anode and cathode usually between 20000 and 140000 volts
Anode material - tungsten or molybdenum
Atomic number of absorbing material

116
Q

Risk from modern day x-rays

A

1 year natural radiation - 3mSv
Chest X-ray- 0.1mSv
Body CT scan - 10mSv
Head CT scan - 2mSv

117
Q

What is the basis of MRI scanners?

A

Protons and neutrons spin which gives a magnetic field. 1.5-3 Tesla = magnetic field. Receiver coil must have a good fit-better inductive coupling

118
Q

What is the cost of scanners?

A

CT scanner - £600,000

MRI - £800,000

119
Q

Compare CT and MRI scanners

A

CT>MRI for resolution

CT<MRI for contrast

120
Q

What are the basic principles of CT scanners?

A

3rd generation scanners- linear array of 500 detectors, single X-ray tube rotation movement only.
1/2second per slice

121
Q

What do CT scanners allow?

A

1- reduction in overlapping structures -> contrast resolution
2- calculation of attenuation coefficient of each voxel-> hounsfield unit
HU: -1000(air) 0(water) +1000(metal)

122
Q

What is a pixel?

A

Mean attenuation of tissue
2D
Based on matrix size and attenuation of tissue

123
Q

What is a voxel?

A

Thickness of CT slice

3D unit

124
Q

Which investigation has the best spatial resolution?

A

Chest X-ray

125
Q

Which investigation has the best contrast?

A

MRI scanners

126
Q

Which investigation has the best functional resolution?

A

PET scan

127
Q

Which investigation is the best compromise?

A

CT scan

128
Q

Why is ultrasound useful?

A

Cheap, quick, and safe

129
Q

What are the advantages of spiral CT scans?

A

Faster scans -> thinner scan possible

No mis-registration of slices due to respiration

130
Q

What are the improvements for spiral CT?

A

Speed
Power
Detail
Volumetric scanning

131
Q

Side effects of contrast?

A

Exacerbation of renal impairment

132
Q

How is contrast given and why?

A

Given to enhance images. Given by Intra-venous, Intra-arterial,oral, negative (air/fat) or positive (iodinated)

133
Q

Advantages and disadvantages of positron emission tomography

A

Sensitive test but difficult to quantify
Best functional
Specialised equipment - 18 FDG PET -> mirrors high glucose tumour
PET in oncology- better spatial resolution

134
Q

What is the standard uptake value (SUV)?

A

Injects standard amount of contrast and measures the activity by using PET cameras. Records activity per volume of tissue and expressed as SUV units.
SUV over 2.5 = suspicious of malignancy

135
Q

What are the risks of radiation?

A

Stochastic - chance of effect increases with exposure. DNA damage and failure it repair.

Non stochastic - effect increases with exposure, will occur over a threshold

136
Q

What do TEOAE do?

A

Stimulate then record

137
Q

What do DPOAE do?

A

Stimulate and record simultaneously

138
Q

What is the Doppler equation?

A 
Fd=2vftCosø/c
V= velocity of blood
2= as signal returns
C= constant
Ft= frequency of transducers
Ø= (meant to be a pheta) angle of transducers to angle of blood flow
139
Q

How is sleep staged?

A

Rechtschaffen and Kales - 30 seconds epoch

ssc (1 decks)

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