Physiological Measurement Flashcards
(140 cards)
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
1
Q
Define precision
A
How reproducible the results are. Clustering
2
Q
What is diagnostic accuracy?
A
Measure of reproducibility, sensitivity, specificity, predictive value, measurement complexity.
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
4
Q
What is specificity?
A
[ TN/all without disease (TN + FP)] x100
True -‘ve rate. Likelihood that the test is actually negative
5
Q
What is the normal hearing range for a human adult?
A
20-20,000 Hz
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
7
Q
What can you examine when viewing with an otoscope?
A
Outer ear, middle ear and ear canal
8
Q
What ear examinations are subjective?
A
Weber test, rinne test, pure tone audio gram, speech audiometry, paediatric audiometry
9
Q
Which ear examinations are objective?
A
Tympanometry, otoacoustic emissions, electrocochleography, auditory brain stem response, cortical evoked responses.
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
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
12
Q
What are the advantages of a tuning fork assessment?
A
Simple
Minimal equipment
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
14
Q
What sort of test is a tuning fork assessment?
A
Psychophysical - tests whole auditory pathway
15
Q
What sort of assessment is pure tone audiogram?
A
Psychophysical
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
17
Q
What are the advantages of a pure tone audiogram?
A
Quantitative measure
Standardised
Differentiate between causes
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
19
Q
What sort of hearing test is speech audiometry?
A
Psychophysical
20
Q
Explain speech audiometry
A
Pre recorded speech material at different intensities consisting of 3 phonemes
21
Q
What are the advantages of speech audiometry?
A
Physiologically relevant
Differentiate between losses
Help rehabilitation
22
Q
What the limitations if speech audiometry?
A
Speech not in all languages
Degree of cooperation
Not in young or limited understanding
23
Q
What sort of test is paediatric audiometry?
A
Psychophysical
24
What are the different hearing tests for varying paediatric ages?
6-18 months - distraction testing
18-30 - cooperation testing - visual reinforcement
30+ - performance testing
25
What are the sources of error in paediatric audiometry?
```
Visual cueing
Auditory cueing
Distractor technique
Tactile cueing
Olfactory cueing
Rhythmic stimulation
```
26
What can be viewed by tympanometry?
Outer ear, ear canal and middle ear
27
How do you perform tympanometry?
Measure of tympanic membrane integrity. Pure tone played into ear canal, intensity monitored whilst static pressure is applied. Results expressed as compliance
28
What are the advantages of tympanometry?
Simple and quick
| Minimal cooperation
29
What are the disadvantages of tympanometry?
Airtight sealed required
| Not measure of hearing
30
What are the different types of otoacoustic emissions?
SOAE - spontaneous otoacoustic emissions
TEOAE - transient evoked otoacoustic emissions
DPOAE - distortion product otoacoustic emission
31
What are you testing for using otoacoustic emissions?
Outer hair cells of the cochlea
| Comparison between the frequency content of the stimulus and emission determines integrity.
32
What are the advantages of otoacoustic emissions?
Non-invasive
Quick, minimal patient cooperation
All ages
Reliable
33
What are the disadvantages of otoacoustic emissions?
Not measure perception
Results don't quantify cochlear sensitivity
Responses abolished with hearing losses above 30-40dB
34
Which sections of the hearing pathway does electrocochleography examine?
Outer ear, ear canal, middle ear, cochlea outer hair cells, cochlea inner hair cells, vestibulocochlear nerve (CN VIII)
35
What does electrocochleography test for?
Functional integrity of the cochlea. Series of clicks and tones
36
What are the advantages of electrocochleography?
Objective
Response not affected by sleep, sedation or general anaesthesia
Intra-operative monitoring
37
What are the disadvantages of electrocochleography?
Not perception
Procedure in invasive
Normative data required for comparison
Below 1KHz not obtained reliably
38
What does auditory brain stem response test for?
Outer ear to -> brain stem
Electrical potential originating from auditory nerve/brain stem- evoked by stimulation of cochlea.
Procedure = objective. Needs minimal myogenic activity
39
What are the uses for auditory brainstem responses?
Screening of newborns hearing
| Intra-operative monitoring
40
What are the advantages of auditory brainstem responses?
Objective
Not influenced by sleep, sedation, or general anaesthesia
Intra-operative monitoring
41
What are the disadvantages of auditory brainstem responses?
Small signal - interference
Relaxed, asleep
Not test of perception
No info beyond brainstem
42
What is cortical evoked responses (CERA) assessing?
Outer ear -> primary cortex
Evaluation of: - inconsistent or unreliable results
- unwilling to participate with subjective testing
- medico-legal cases with no organic cause
43
What are the advantages of cortical evoked responses?
Objective
Assessment of high auditory function
Absence of cortical/perceptual deficit, frequency specific threshold within 5-10dB of patients subjective threshold
44
What are the disadvantages of cortical evoked responses?
```
Not test perception
Large degree of inter/intrasubject variability
Affected by patients alertness
Not suitable for paediatrics
Time-extensive. Up to 1 hr
```
45
What can be detected on spirometry?
Excessive mucus secretion
narrowing of airways - asthma, inflammation or oedema
loss of radial traction - emphysema
46
When the pressure is large in the thorax, when do the airways collapse?
Expiration
47
what is the purpose of helium dilution?
measures volume of gas that is in communication with the airway opening. i.e. the vol. that is ventilated.
48
what is the calculation to figure out the volume after a helium dilution?
v1C1=V2C2
v1 - starting volume of spirometer
c1- starting concentration of helium
v2- final volume (lungs and spirometer)
c2 - final concentration of helium
49
what is measured on spirometry?
fvc - forced vital capacity
| FEV1 - forced expiratory volume in 1 second
50
Explain a nitrogen washout
- single breath to residual volume
- max inspiration of pure oxygen
- breath out regularly and slowly, record levels of N2 on expiration
51
what happens to the concentration of nitrogen exhaled in asthmatics?
increases
52
what happens to the concentration of nitrogen exhaled in ciliary dyskinesia?
decreases
53
what is detected on an induced sputum?
cells of inflammation.
| hypertonic saline solution inhaled which induces coughing and sputum
54
What are predictive values for respiratory investigations based on?
height
| values from literature
55
What are the two diodes involved in oximetry?
Red light and infrared
56
What are the limits for oximetry in an adult?
HR - 140/55
| Sat - 100/85
57
What are the limits for oximetry in a baby?
HR will be higher
| Sat - 100/85
58
Why might oxygen saturation be less than 100%?
Branchial veins drain directly into pulmonary vein
| Varying types of Hb
59
How to measure exercise induced asthma?
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
What is investigated during plethysmography?
Changes in vol of organ or whole body
| Measure thoracic gas vol and airway resistance.
61
What is plethysmography good for?
Hyperinflation
62
How is plethysmography carried out?
The pt sits in airtight cabin, breathe through pneumotachograph, a shutter will close the device occluding external airway-> fixed vol and temp
63
What is the calculation for Functional residual capacity?
Resistance = pressure x flow
64
What are the uses for chemical pathology?
Make diagnosis/confirm diagnosis
Monitor disease - routine biochemistry, tumour markers, hormone assays
Drug monitoring
Screening
65
Define standard deviation
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
Define False positive rate
The proportion of tests which give a positive result who don't have the condition
67
Define true positive
Positive test result and actually have the condition
68
Define true negative
Negative result and don't have the condition
69
Define false negative
Negative test result but does have the condition
70
Prevalence value
True positive/(true positive + false positive) x 100
71
What happens in obstructive jaundice?
Elevated ALP - bone, liver, intestine, placenta
72
What happens in heptocellular jaundice?
Elevated ALT- liver
73
What happens in mixed jaundice?
Both ALT and ALP are elevated
74
What happens during a stress test when a patient has a growth hormone deficiency?
Infusion of insulin. Growth hormone and cortisol elevated.
Glucose must be below 2.2 for results to be effective
75
What are the symptoms of hyperpituitarism?
```
Visual field defects
Hypertension
Headache
Facial changes and fatal
Increased growth hormone
```
76
How do you calculate the ankle brachial pressure index (ABPI)?
KAnkle systolic/brachial systolic
Less than 1 = abnormal
Greater than 1 = normal
77
What are the characteristics of ultrasound waves?
Loudness/amplitude
Frequency
Speed
Reflection - speculation at large surfaces. Scattering at small surfaces
78
How does ultrasound work?
Uses a transducer with piezoelectric crystals -> change shape when a voltage is applied
79
What characteristics does a flat linear probe have?
High frequency
High resolution
Poor penetration
80
What characteristics does a domed transducer have?
Low frequency
Lower resolution
Greater penetration
81
What is the brightness of an ultrasound image dependent on?
The intensity of the reflection
82
What are the different types of Doppler?
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
Describe the 3 waves seen on a spectral Doppler?
Triphasic - normal in peripheral arteries
Biphasic- arterial stiffness
Monophasic - significant arterial disease. Renal and carotid arteries
84
What is aliasing?
Speed of sampling is too slow so looks as if blood flow is moving backwards
85
Explain the follow up to different sized abdominal aortic aneurysms?
<3cm = fine
| 3-5.5cm - 1% rupture risk
86
Problems with venous disease?
Reflux - colour
| Dvt - veins don't collapse if clot present. In advanced diabetes, element of vein calcification
87
Explain the difference in sizes of nerves
Motor - largest - myelinated
Sensory - thinly or not myelinated
Autonomic - smallest
Conduction velocity - faster in the largest
88
What does an EMG machine record? (Electromyography)
Velocity and amplitude of action potential
Sensory nerve action potential (SNAP)
Compound motor action potential (CMAP)
89
What is recorded from a motor neuron?
Start at 0mA and increase to 20/30mA
| Record amplitude and duration
90
What is recorded from a sensory neuron?
Purely sensory portion of nerve. Recording electrode must be proximal.
Amplitude less than motor
Duration - shorter than CMAP - measure of synchrony
91
What are the limitations of an EMG machine?
Patient discomfort
Patient factors - movement, temp of limbs, peripheral oedema, inaccessible area, syncope
Equipment failure and interference
Over calling abnormalities
92
How is muscle activity recorded?
Needle electrodes - local picture, intramuscular
| Surface electrodes - general picture
93
What are the myotomes?
```
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
How can you interpret nerve damage?
Produce positive sharp waves.
Denervated fibres = 7-10 days
Sound produced by machine is related to the strength of the contraction.
95
How can you interpret muscle damage?
Decreased duration of motor unit action potential
| Decreased amplitude
96
What are the limitations of EMG?
Technical interference, operator dependent,
| Clinically invasive, risk of haematoma
97
How is brain activity recorded?
EEG-electroencephalogram. Records electrical activity within brain.
Depth - dural or scalp.
Even numbers - right hand side. Odd numbers - left hand side. Z=midline.
98
What are the normal wavelengths seen in brain activity?
Delta 13Hz
Montages - bipolar, referential, average.
99
When is EEG used clinically?
Diagnosing epilepsy and localising site of seizure
Evoked potentials: visual evoked potentials
Somatosensory evoked potentials
100
What are the advantages of evoked potentials?
Cheap, portable,non-harmful, excellent temporal resolution
101
What are the disadvantages of evoked potentials?
```
Poor spatial resolution, must be trained staff
Artefacts: biological
Environmental
Technical
Patient cooperation
```
102
What are the stages of sleep?
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
Name some disorders of initiating and maintaining sleep
```
Insomnia
Depression
Paradoxical insomnia
Poor sleet hygiene
Drug induced
Fatal familial insomnia
```
104
Explain a primary sleep disorder such as narcolepsy
```
Excessive daytime sleepiness
Hallucinations >10 mins
Sleep paralysis
Disturbed night sleeping
Cataplexy
```
105
Explain a secondary sleep disorder such as obstructive sleep apnoea
Apnoea -100% for 10 secs
Hypopnoea - 50% decrease over 10 secs
Apnoea:hypopnoea index mild=5-14
Moderate =15-29
Severe = >30
106
What are parasomnias?
Abnormal sleep behaviour and movements
107
How is sleep assessed?
Diary
Actigraphy- detection of movement
Polysomnography - gold standard but expensive
108
How is wakefulness assessed?
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
Why are radiological images used?
To "look inside" the patient
To confirm a diagnosis and or rule out a condition
Because the patient expects it
110
Explain probability.
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
Explain Bayes' Theorem
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
In ultrasound the spacial detail available depends on frequency, explain
High frequency - higher resolution
Low frequency - better depth penetration
Doppler - shift in sound frequency indicates motion. Common application to measure blood flow
113
What are the different types of nuclear medicine?
Scintigraphy: produces plain 2D picture. Iodine scan for hypo/hyperthyroidism
Single photon emission computed tomography (SPECT): 3D picture produced. Gamma ray emitting radiopharmaceutical
114
Explain the basis of positron emission tomography (PET)
Uses beta-particle emitting pharmaceutical
| Beta particle decays to emit an electron and positron. 3D picture produced - fluoro-deoxy glucose
115
What does x-ray absorption depend on:
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
Risk from modern day x-rays
1 year natural radiation - 3mSv
Chest X-ray- 0.1mSv
Body CT scan - 10mSv
Head CT scan - 2mSv
117
What is the basis of MRI scanners?
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
What is the cost of scanners?
CT scanner - £600,000
| MRI - £800,000
119
Compare CT and MRI scanners
CT>MRI for resolution
| CT
120
What are the basic principles of CT scanners?
3rd generation scanners- linear array of 500 detectors, single X-ray tube rotation movement only.
1/2second per slice
121
What do CT scanners allow?
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
What is a pixel?
Mean attenuation of tissue
2D
Based on matrix size and attenuation of tissue
123
What is a voxel?
Thickness of CT slice
| 3D unit
124
Which investigation has the best spatial resolution?
Chest X-ray
125
Which investigation has the best contrast?
MRI scanners
126
Which investigation has the best functional resolution?
PET scan
127
Which investigation is the best compromise?
CT scan
128
Why is ultrasound useful?
Cheap, quick, and safe
129
What are the advantages of spiral CT scans?
Faster scans -> thinner scan possible
| No mis-registration of slices due to respiration
130
What are the improvements for spiral CT?
Speed
Power
Detail
Volumetric scanning
131
Side effects of contrast?
Exacerbation of renal impairment
132
How is contrast given and why?
Given to enhance images. Given by Intra-venous, Intra-arterial,oral, negative (air/fat) or positive (iodinated)
133
Advantages and disadvantages of positron emission tomography
Sensitive test but difficult to quantify
Best functional
Specialised equipment - 18 FDG PET -> mirrors high glucose tumour
PET in oncology- better spatial resolution
134
What is the standard uptake value (SUV)?
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
What are the risks of radiation?
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
What do TEOAE do?
Stimulate then record
137
What do DPOAE do?
Stimulate and record simultaneously
138
What is the Doppler equation?
```
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
How is sleep staged?
Rechtschaffen and Kales - 30 seconds epoch
