Trans-oesophageal echocardiography

Concerning trans-oesophageal echocardiography

(a) the Doppler probe employs high-frequency sound waves

(b) the Doppler effect is due to a change in frequency of the ultrasound waves

(c) ultrasound gives a precise measure of cardiac output

(d) the speed of medical ultrasound is 1540 m/s

(e) medical ultrasound passes better through air than blood

Strain gauge

A strain gauge can be used to measure

(a) gas flow

(b) intensity of light

(c) arterial blood pressure

(d) forearm blood flow

(e) force of muscle contraction

Electrical safety

Regarding electrical safety

(a) an electrical current of 5mA passing through the body will cause a tingle

(b) class II electrical equipment must be double insulated

(c) class III equipment can only work with a low voltage (<24 V)

(d) the leakage current from any equipment that can come in contact with the heart must be less than 50mA

(e) anaesthetic proof (AP) may be used in the zone of risk 5–25cm from an enclosed medical gas system

Student’s t-test

Student’s t-test

(a) is used to analyse normally distributed data

(b) is used for comparing a single small sample

(c) should be used as a one-tailed test whenever possible

(d) deals with the problems associated with inference based on ‘small’ samples

(e) is typically used to compare the means of two populations

Haemofiltration

 Regarding the physiological principles underlying haemofiltration

(a) the pore size of the membrane allows molecules up to 50, 000 daltons to pass through

(b) an ultrafiltrate of up to 1000 ml per hour can be formed

(c) plasma water is removed by convective flow

(d) the buffer of choice is bicarbonate in very low concentrations

(e) transmembrane potential equals hydrostatic pressure _ oncotic pressure

Medical piped gases

With regard to medical piped gases

(a) the nitrous oxide pressure is 4 bar (4 · 105 Pa)

(b) after maintenance of O2 pipes the O2 analyser is used to test the integrity of the system

(c) the non-interchangeable screw thread (NIST) has one diameter in the shaft which is specific for each gas

(d) the Schrader probe has a non-return valve (e) the pipeline oxygen supply pressure enters the machine at 420 kPa (60 psi) pressure

Substance conversion

With regard to a substance

(a) 1 mol equals 0.012 g carbon-12

(b) 1 mol occupies 2.24 l at s.t.p.

(c) In 1 mol of any substance are 6.022 · 1023 molecules

(d) mole is the SI unit of volume

(e) one gram molecular weight of any gas occupies the same volume

Pressure conversion

A pressure of 1 bar is equal to

(a) 1 kg/cm

(b) 14.5 lb/in

(c) 7.5 torr

(d) 1006.2 cmH2O

(e) 101.01 pascal

Plethysmography

Plethysmography is used to measure

(a) total lung capacity

(b) functional residual capacity

(c) residual volume

(d) forearm blood flow

(e) coronary blood flow

Surface tension

Surface tension

(a) is measured in newtons per metre

(b) in the wall of a sphere, is directly proportional to the diameter of the sphere

(c) is due to attraction between molecules in a liquid (molecular cohesion)

(d) leads to a water manometer under-reading

(e) leads to a mercury manometer over-reading

Linear regression analysis

Linear regression analysis

(a) applies a technique of minimising squared differences

(b) can be used to analyse variables that are not distributed normally

(c) gives a regression coefficient

(d) yields an intercept that defines the position of the line

(e) finds the line that best predicts X from Y

Transfer of heat

The following are true of the transfer of heat

(a) an adiabatic change retains the heat of the reaction within the system

(b) boiling involves transferring heat without a change in temperature

(c) a body with a high heat capacity will transfer heat to one with a lower heat capacity at the same temperature

(d) radiation is proportional to the fourth power of the absolute temperature

(e) the response time of a thermometer increases with its heat capacity

Transcutaneous electrical nerve stimulation

Transcutaneous electrical nerve stimulation

(a) uses a current up to 90mA

(b) uses a frequency of 0–100 Hz

(c) pulse duration is 0.1–0.5 ms

(d) at low frequency acts by closing the gate

(e) at high frequency acts by releasing endorphin

Agent specific

The following are agent specific

(a) mass spectrometry

(b) ultraviolet analyser

(c) infrared analyser

(d) piezoelectric analysis

(e) refractometer

Measurement of gas volume

The gas volume can be measured accurately using a

(a) Wright’s respirometer

(b) vitalograph

(c) Benedict Roth spirometer

(d) dry gas meter

(e) pneumotachograph

Serum osmolarity

Serum osmolarity is

(a) a measure of the number of particles in solution

(b) usually expressed in milliosmoles per litre

(c) commonly determined by the temperature at which a solution freezes

(d) proportional to the valency of the particles in solution

(e) dependent on the serum albumin concentration

Nerve stimulators

The following are true of nerve stimulators

(a) the applied electrical potential can be as high as 150 V

(b) the apparatus uses a square-wave electrical signal

(c) the pulse current should be 0.5–5.0mA when skin electrodes are used

(d) when the resistance increases the current must decrease, at a constant voltage

(e) stimulation at a constant current is preferable to stimulation at constant voltage

Pneumotachograph

The pneumotachograph

(a) directly measures change across a resistance

(b) must have a resistance of sufficient diameter to ensure laminar gas flow

(c) is not suitable for accurate breath-by-breath monitoring

(d) possesses accuracy affected by temperature change

(e) possesses accuracy unaffected by alterations in gas composition

Oxygen for medical use

Oxygen for medical use

(a) is prepared by the fractional distillation of air

(b) for pipelines contains 0.3% nitrogen

(c) forms an inflammable mixture with oil

(d) from concentrators provides an FiO2 of over 80%

(e) has similar magnetic properties to nitrous oxide

Transoesophageal Doppler

Transoesophageal Doppler

(a) requires a probe of 50–60 cm length

(b) gives information about stoke volume

(c) readings are affected by temperature

(d) measures the blood velocity in the ascending aorta

(e) uses acceleration and peak velocity to indicate myocardial performance

Oxygen analysis

Principles involved in oxygen analysis intraoperatively include 

(a) the volumetric method

(b) Graham’s law

(c) oxygen extraction

(d) paramagnetism

(e) absorption of oxidative energy

Pressure gauges

Pressure gauges

(a) reduce high pressures to low pressures

(b) regulate flow from a cylinder

(c) are calibrated in pascals

(d) form part of a device for measuring gas flow

(e) utilise the principle of the Burdon gauge

Statistical tests

Regarding statistical tests

(a) the middle observation in an ordered series is the median

(b) the mean is the most frequently occurring observation in a series

(c) the standard deviation gives an indication of the scatter of the observations

(d) 95% of all values lie within ±2 SD

(e) the standard deviation is a measure of the significance of observations

Surgical diathermy

Regarding surgical diathermy

(a) the degree of burning at the tip of an active electrode is dependent on the current density

(b) bipolar diathermy operates at a higher power output than unipolar diathermy

(c) if the plate is detached the current will not flow

(d) the current frequency is the same at the active electrode and at the patient’s plate

(e) isolating capacitors are used because they have low impedance to a low-frequency current

SI unit

The correct SI unit for

(a) time is the second

(b) mass is the gram

(c) force is the pascal

(d) energy is the watt

(e) length is the metre

Classification of electrical medical devices

The following statements apply to the classification of electrical medical devices

(a) class I is represented by the symbol &

(b) class III can be connected to the mains

(c) type CF must have a leakage current of <25 mA

(d) type B can be class I, II or III

(e) class I requires a single fuse

Liquid vaporisation

The ease with which a liquid will vaporise is related to

(a) the latent heat of vaporisation of the liquid

(b) the latent heat of crystallisation of the liquid

(c) the blood/gas solubility coefficient

(d) the density of the liquid

(e) the specific gravity of the liquid

Properties of a capacitor

The following are properties of a capacitor

(a) a capacitor consists of two conductor plates separated by an insulator

(b) the size of a capacitor depends on the number of turns of wire around the coil

(c) the size of a capacitor depends on the surface area of the plates

(d) the unit of capacitance is the joule

(e) AC current flow ceases through a capacitor when fully charged

Critical temperature of a gas

The critical temperature of a gas 

(a) is the temperature above which a gas cannot be liquefied

(b) is the temperature below which it requires a lower pressure to liquefy a gas

(c) varies with pressure

(d) is the temperature at which a gas exists simultaneously in the gaseous and liquid states at atmospheric pressure

(e) is the temperature at which oxygen is liquefied by a pressure of 50 bar

Laminar flow through a horizontal tube

Laminar flow through a horizontal tube has the following characteristics

(a) flow rate is proportional to the viscosity

(b) flow rate is inversely proportional to the density

(c) flow rate is inversely related to the length of the tube

(d) flow rate is turbulent when the Reynolds number is larger than 4000

(e) velocity at the centre of the tube is greater than at the sides

Glibenclamide

Glibenclamide

(a) may cause hypoglycaemia

(b) increases secretion of insulin

(c) increases the peripheral action of insulin

(d) causes lactic acidosis

(e) is excreted by the kidney

Heparin

The following are side-effects of heparin

(a) thrombocytopenia

(b) urticaria

(c) intrauterine fetal haemorrhage

(d) osteoporosis

(e) alopecia