Answer ALL FIVE questions. Please use a separate answer book for each
question.
The marks given in square brackets at the right hand side indicate the marks carried by
that part of the question. Approved electronic calculators may be used.
1. (a) Brain-computer interfaces allow users to interact with their environments,
without needing to use their peripheral nervous systems. Instead, their brain
signals can be recorded non-invasively using electroencephalogram (EEG),
which is then processed and classified to replace a traditional user input in an
assistive technology. Figure 1.1 shows a typical evoked potential that is used by
some brain-computer interfaces (BCis ).
(i) What are the names given to each of the peaks and troughs shown in [1]
Figure 1.1
(ii) What does 0 ms represent on the time axis [1]
(iii) What typically causes the feature of the signal shown at approximately [ 1]
400 ms in Figure 1.1
(iv) Describe a brain-computer interface paradigm that exploits this feature [3]
(depicted in Figure 1.1) and explain how a typical application works.
(v) An alternative BCI paradigm is motor imagery. What are the main EEG [2]
features that are used to build motor-imagery classifiers
(vi) What advantages does motor imagery have over the paradigm that uses [2]
the features in Figure 1.1
> ::1.
._.
p
~
c:
~
￡
-3
3
0 100 200 300 400 500
Tlme (ms)
Figure 1.1 An evoked potential recorded from the Cz electrode
that is used by some brain-computer interfaces.
(b) Describe three ways to compare the haptic performance ofbackdrivable and
non-backdrivable devices. Using example devices such as the Novint Falcon [10]
and the Haptic Master, compare critically the haptic interfaces ofbackdrivable
and non-backdrivable devices.
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2. (a) A young child patient suffers from hypothermia and has a body temperature
of 36 °C. The patient is being seen by a nurse in the clinic with a room
temperature of 33 oc and relative humidity of 80%. The nurse uses a spirometer
to measure the tidal volume of the patient’s lungs which is 0.3 litres.
Suppose the tidal volume corrected for Body Temperature Pressure Saturated
(BTPS) is 0.31 litres, calculate the saturated water vapour pressure, pH20* at
36 oc in Table 2.1. [0 oc = 273 K, atmospheric pressure= 760 mmHg]
Temperature 31 32 33 34 35 36 37 38 39 40
(°C)
pH20* 33.7 35.7 37.7 39.9 42.2 47.1 49.7 52.4 55.3
(mmHg)
Table 2.1 Saturated water vapour pressure, pH20* at vanous temperatures
(b) Lung conditions such as emphysema and bronchial asthma can be diagnosed
by a lung function test based on forced expiration.
[5]
(i) How is the intrapleural pressure in normal expiration different from that in [ 1]
forced expiration
(ii) What is the difference between the alveolar pressure of a healthy subject
and that of a patient suffering from emphysema Explain the cause of this [2]
change in the emphysema patient.
(iii) Figure 2.1 depicts the airway pressure from the alveolus to the mouth
during forced expiration for an emphysema patient. Redraw the diagram and [ 1]
add a line to represent the airway pressure for a healthy subject.
(iv) Comment on the flow rate of the emphysema patient during forced
expiration in comparison to that of a healthy subject. Explain what causes this
change in the forced expiratory flow rate in the emphysema patient. (You can [2]
refer to the diagram drawn in Question 2(b )(iii) to elaborate your answer.)
(v) Draw the spirograms of a healthy subject and an emphysema patient. Label [2]
the measurements FEV1 (Forced Expiratory Volume in 1 second) and FVC
(Forced Vital Capacity).
Airway Pressure
.__ Emphysema patient
—— ·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·-·- —— —— .__
—— 0 ~——————~~————
Intrapleural Pressure
Alveolus Mouth Airways
Fig.2.1 Pressure during forced expiration for an Emphysema patient
PAPER CONTINUES
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2. (continued)
(c) Carbon monoxide (CO) and helium are used in a breath holding test to
measure the diffusing capacity of the lung for carbon monoxide (DLCO).
(i) Why isn’t the diffusing capacity of the lung for oxygen (DL02) measured [1]
directly instead
(ii) What is the function of helium in this test What is the advantage of using [2]
helium
(iii) Provide two advantages of using carbon monoxide in this test. [2]
(iv) What is the equation that models the clearance of carbon monoxide inside
the lungs, showing the drop of mole fraction of CO, Fco(t) over time Suppose
the mole fraction of CO at the beginning of the test and after 10 seconds are [2]
Fco(O) = 0.20% and Fco(JO) = 0.05%, respectively. Calculate the rate constant
of the decay.
3. (a) Draw a labelled diagram of the anatomy of the male lower urinary tract. [ 4]
(b) Uroflowmetry is a diagnostic test to measure the amount of urine voided during
urination, and the speed ofurination.
(i) Outline the steps involved in completing a clinical uroflowmetry test. [2]
(ii) Sketch a typical normal flow rate I time profile from such a measurement. [ 4]
Indicate the clinically relevant measurements taken from the trace.
(c) To diagnose the bladder and urethral function during a micturition cycle,
cystometry (urodynamics) is carried out.
(i) Provide TWO different reasons to explain why the patient is asked to cough [2]
during the test
(ii) How do you measure detrusor pressure Describe the measuring devices [2]
and how they are used.
(d) To manage incontinence, various treatments can be adopted. Describe THREE [6]
ways to manage incontinence using behavioural, physiotherapy or surgical means.
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4. Considering the main stages in making high quality recordings ofbiopotentials in
medicine in an electromyogram (EMG) or nerve conduction study system, discuss
these stages:
(a) What is the measured variable and why is it chosen
(b) What properties are needed from skin electrodes
(c) Why is an earth needed
(d) What amplifier type is needed and why
(e) What signal processing is used and why
5. (a) The strength-duration curve may be represented by a formula with the form:
(Equation 5 .1)
[4]
[4]
[4]
[4]
[4]
where ‘ y and 8 represent the variables or constants in Table 5.1. Re-write this [5]
formula, replacing a, ‘ y and 8 with the variables and constants given in Table 5 .1.
variable lth threshold current
variable t pulse width
constant lrh rheobase
constant T chronaxie
Table5.1
(b) For an experiment, stimulating electrodes are placed so that they are closer to
a nerve with pain fibres than to the target motor nerve. The strength-duration
curves for muscle contraction and pain have the following constants (Table 5.2).
The experiment requires that for a given pulse width, the current amplitude is
increased to twice motor threshold. If at that amplitude, pain can just be felt, what
is the pulse width
muscle contraction rheobase lOrnA
chronaxie 0.2ms
pam rheobase 3mA
chronaxie 3 ms
Table 5.2
END OF PAPER
