RCOA Guide to the FRCA Examination The Primary (fourth edition) - Physics, Equipment & Monitoring, and Statistics MTF

Question 1

When measuring central venous pressure:

A catheter inserted in an adult at the antecubital fossa should be passed no more than 20 cm up the vein

Answer 1

False. The tip of the catheter should be within superior vena cava and that distance will vary between patients.

Question 2

When measuring central venous pressure:

The optimum internal diameter for the catheter is 0.25 mm

Answer 2

False. The usual adult size catheters are 14-16 Gauge, corresponding to 1.63 and 1.3 mm diameter.

Question 3

When measuring central venous pressure:

Direct subclavian vein catheterisation can be used

Answer 3

True. Either internal jugular or subclavian vein could be used as long as the catheter tip is located in the superior vena cava.

Question 4

When measuring central venous pressure:

Microshock is a potential hazard

Answer 4

True. Microshock is a term describing the induction of ventricular fibrillation by small electrical currents (below the threshold of skin sensation, i.e. below 1 mA) when applied to very small areas of ventricular muscle, usually by vascular catheters or wires. It requires a small area of contact with heart muscle so that the current density is high despite low current.

Question 5

When measuring central venous pressure:

The zero level should be set at the level of the angle of Louis
whatever the position of the patient

Answer 5

False. It is usually set at the point where the fourth intercostal space and mid-axillary line cross each other. This allows the measurement to be as close to the right atrium as possible with the patient in a supine position.

Question 6

A liquid inhalational anaesthetic agent is allowed to come into equilibrium with a mixture of gases. Under these conditions, the partial pressure of the agent in the resulting gas mixture depends on:

The atmospheric pressure

Answer 6

False. At this point an inhalational agent will be at its saturated vapour pressure (SVP). It is only the temperature of the liquid that influences the SVP. The higher the temperature, the higher the SVP.

Question 7

A liquid inhalational anaesthetic agent is allowed to come into equilibrium with a mixture of gases. Under these conditions, the partial pressure of the agent in the resulting gas mixture depends on:

The surface area of the liquid

Answer 7

False. At this point an inhalational agent will be at its saturated vapour pressure (SVP). It is only the temperature of the liquid that influences the SVP. The higher the temperature, the higher the SVP.

Question 8

A liquid inhalational anaesthetic agent is allowed to come into equilibrium with a mixture of gases. Under these conditions, the partial pressure of the agent in the resulting gas mixture depends on:

The volume of the liquid

Answer 8

False. At this point an inhalational agent will be at its saturated vapour pressure (SVP). It is only the temperature of the liquid that influences the SVP. The higher the temperature, the higher the SVP.

Question 9

A liquid inhalational anaesthetic agent is allowed to come into equilibrium with a mixture of gases. Under these conditions, the partial pressure of the agent in the resulting gas mixture depends on:

The composition of the gas mixture

Answer 9

False. At this point an inhalational agent will be at its saturated vapour pressure (SVP). It is only the temperature of the liquid that influences the SVP. The higher the temperature, the higher the SVP.

Question 10

A liquid inhalational anaesthetic agent is allowed to come into equilibrium with a mixture of gases. Under these conditions, the partial pressure of the agent in the resulting gas mixture depends on:

The temperature of the liquid

Answer 10

True. At this point an inhalational agent will be at its saturated vapour pressure (SVP). It is only the temperature of the liquid that influences the SVP. The higher the temperature, the higher the SVP.

Question 11

The correct SI unit for:

Force is the pascal

Answer 11

False. Pascal is the Sl unit of pressure. 1Pa = 1N/m^2.

Force is expressed in Newtons. 1N=1kg.m.s^-2: A force of 1 N will give a mass of 1 kg an acceleration of 1 m per second.

Question 12

The correct SI unit for:

Mass is the gram

Answer 12

False. The Sl unit of mass is the kilogram.

Question 13

The correct SI unit for:

Time is the second

Answer 13

True

Question 14

The correct SI unit for:

Length is the metre

Answer 14

True

Question 15

The correct SI unit for:

Energy is the watt

Answer 15

False. Watt is a derived unit of power (the rate of doing work, J S^-1).

The unit of energy is Joule. 1J = 1 N.m. One Joule is the energy expended when the point of application of a force of 1N moves 1 m in the direction of the force.

Question 16

The following are true of critical temperature:

Critical temperature is the temperature above which a substance cannot be liquefied however much pressure is applied

Answer 16

True. This is a definition of critical temperature.

Question 17

The following are true of critical temperature:

The critical temperature of oxygen is -119°C

Answer 17

True.

Question 18

The following are true of critical temperature:

Nitrous oxide cylinders always contain liquid nitrous oxide

Answer 18

False. At the very end of its use, there is no liquid left in the cylinder only vapour. This is when the pressure in the cylinder starts to drop rapidly. In addition, at temperatures above its critical temperature the cylinder will contain only gas.

Question 19

The following are true of critical temperature:

The critical temperature of nitrous oxide is 48.5°C

Answer 19

False. The critical temperature of nitrous oxide is 36.5°C.

Question 20

The following are true of critical temperature:

Critical pressure is the vapour pressure of a substance at its critical temperature

Answer 20

False. The critical pressure of a substance is the pressure required to liquefy a gas at its critical temperature.

Question 21

According to laws of physics:

Boyle’s Law assumes that molecular size is unimportant

Answer 21

True. Boyle’s Law is an ideal gas law and assumes among other things that molecular size is unimportant.

Question 22

According to laws of physics:

Boyle’s Law states that the volume of a gas varies inversely with pressure

Answer 22

True. This is the definition of Boyle’s Law

Question 23

According to laws of physics:

Charles Law predicts that as the temperature of a mass of gas is raised from 10°C to 20°C its volume will double.

Answer 23

False. Charles Law states that at a constant pressure, the volume of a given mass of gas varies directly to its absolute temperature. Absolute temperature is measured in Kelvin. 0°C = 273K. Hence, 10°C= 10+273=283K and 20°C=20+273=293K. So, when temperature rises from 10 to 20°C the pressure only goes up by 3.5% (it does not double). The temperature change in Kelvin is only 10K (10K is 3.5% of the initial 283K).

Question 24

According to laws of physics:

Dalton’s Law states that a gas dissolves in proportion to its partial pressure

Answer 24

False. Dalton’s Law states that in a mixture of gases, the pressure exerted by each gas is equal to the pressure which would be exerted if that gas alone were present. Hence, the total pressure exerted by the mixture of gases is equal to the sum of the partial pressures of individual gases.

Question 25

According to laws of physics: Laplace's Law suggests that large alveoli should collapse

Answer 25

False. Laplace's Law for spheres reads P= 2T/r, where P is the pressure gradient across the wall, T is the tangential force acting along the length of the wall and r is the radius. So in large alveoli, the radius will be larger and consequently the resultant pressure gradient across the wall will be smaller. That is why large alveoli do not collapse and there is a tendency of small alveoli to empty into large alveoli. In normal lungs this does not occur due to the presence of surfactant lining the alveoli.

Question 26

The Doppler effect: Applies to both electromagnetic radiation and sound

Answer 26

True. The Doppler effect for electromagnetic waves such as light is invaluable in astronomy. It has been used to measure the speed at which stars and galaxies are approaching or receeding from us.

Question 27

The Doppler effect: Changes the velocity of reflected ultrasound

Answer 27

False. It is the change of frequency of a signal that is key to the Doppler effect.

Question 28

The Doppler effect: Depends on the piezo-electric properties of some crystals

Answer 28

False. That is true of clinical ultrasound but not the Doppler effect.

Question 29

The Doppler effect: Shows a shift to lower frequency if the source is moving away from the receiver

Answer 29

True. And the opposite is correct showing the shift to a higher frequency if the source is moving towards the receiver.

Question 30

The Doppler effect: Can indicate the velocity of red blood cells

Answer 30

True. The sound waves reflect from surfaces of the red blood cells as they approach and move away. Analysis of the reflected frequencies allows determination of velocity of flow.

Question 31

Sevoflurane vapour: Concentration can be measured using a refractometer

Answer 31

True. The refractometer, sometimes called the interferometer can measure the concentration of any inhalational agent. It measures the extent to which light is bent (i.e. refracted) when it moves from air into a sample.

Question 32

Sevoflurane vapour: Is less dense than air

Answer 32

False.

Question 33

Sevoflurane vapour: Absorbs ultraviolet radiation

Answer 33

False. It absorbs infrared radiation.

Question 34

Sevoflurane vapour: Can be measured by absorption of infrared radiation

Answer 34

True. That is the principle of infrared analyser when used to measure the concentration of sevoflurane and other substances containing two dissimilar atoms in a molecule.

Question 35

Sevoflurane vapour: Can be measured by mass spectrometry

Answer 35

True. Mass spectrometry works by ionising chemical compounds to generate charged molecules or molecular fragments. Their mass-to-charge ratios are then measured.

Question 36

The Bain coaxial breathing system: Delivers the fresh gas flow in the outer tube

Answer 36

False. The inner tube carries the fresh gas flow. By contrast, the coaxial Mapleson A system (Lack) carries the fresh gas flow in the outer tube.

Question 37

The Bain coaxial breathing system: Requires a fresh gas flow equal to the patient's minute volume to prevent rebreathing with spontaneous respiration

Answer 37

False. Rebreathing would definitely occur at a fresh gas flow equal to minute ventilation. To prevent rebreathing, a fresh gas flow of 2-4 times per minute ventilation is usually quoted.

Question 38

The Bain coaxial breathing system: Can be used in a child weighing 20 kg

Answer 38

True. In fact, it has been safely used in children weighing less than 20 kg.

Question 39

The Bain coaxial breathing system: Has a dead space which is increased if the inner tube is dislodged at the machine end

Answer 39

True. Apparatus dead space is that volume of a breathing system that contains alveolar gases that are inhaled on a subsequent breath. Following this disconnection, it is increased. Alveolar gases would be pushed towards (rather than away from) the patient by the fresh gas flow risking dangerous accumulation of carbon dioxide.

Question 40

The Bain coaxial breathing system: Can function as a Mapleson C system

Answer 40

False. It is Mapleson D. The Mapleson classification is specific about the spatial relationship between fresh gas flow input, reservoir bag, APL valve and tubing in the system.

Question 41

The following are true of piped gases: The normal pipeline pressure for nitrous oxide is 4.1 Bar

Answer 41

True. Nitrous oxide, oxygen and medical air are all supplied at a pipeline pressure of 4.1 Bar.

Question 42

The following are true of piped gases: The changeover valve incorporated in a cylinder bank works on a pneumatic shuttle mechanism

Answer 42

True. As the pressure within the in-use bank of cylinders falls, a passive shuttle is pushed over by the higher pressure within the adjacent full cylinder bank and a continuous downstream pressure is maintained. No power supply is required, other than to sound an alarm.

Question 43

The following are true of piped gases: The non interchangeability of Schrader valves depends on varying sizes of collars on the probes

Answer 43

True. For safety, the collars are pipeline specific and non-interchangeable. Alongside non-interchangeable screw threads (NIST) on pipeline connections and the pin index system on cylinder yokes, they are key to the safe delivery of the correct gases through an anaesthetic machine.

Question 44

The following are true of piped gases: The Schrader outlet contains an internal non-return valve

Answer 44

True. The outlets feature on both the positive pressure gas and sub atmospheric vacuum pipelines.

Question 45

The following are true of piped gases: When reinstating oxygen pipelines after servicing, testing with an oxygen analyser ensures the integrity of the system

Answer 45

False. An oxygen analyser would detect the presence of oxygen, but not the maintenance of pressure within the pipeline. The latter would also be needed to comment on the integrity of the system.

Question 46

The following are true of the measurement of oxygen concentration: Oxygen is a paramagnetic gas because its molecule has paired electrons in the outer shell

Answer 46

False. Unpaired electrons in the outer shell are needed for paramagnetism. Therefore, magnesium, lithium, molybdenum and tantalum also exhibit paramagnetism.

Question 47

The following are true of the measurement of oxygen concentration: In a paramagnetic analyser, the two glass spheres are filled with oxygen

Answer 47

False. The glass spheres are full of nitrogen which is weakly diamagnetic (slightly repelled by the magnetic field).

Question 48

The following are true of the measurement of oxygen concentration: In a paramagnetic analyser, rotation of the dumb-bell is balanced by torsion in a suspending filament

Answer 48

True. The tension of suspending ligament determines the orientation of the dumb-bell in the magnetic field.

Question 49

The following are true of the measurement of oxygen concentration: In a null-deflection analyser, an opposing magnetic field prevents movement of the dumb-bell

Answer 49

True. In this device, photocells are used to control a variable current that induces a magnetic field that exactly offsets the movement due to the paramagnetic effect of the oxygen. The current is used to calculate the oxygen concentration.

Question 50

The following are true of the measurement of oxygen concentration: Water vapour affects paramagnetic oxygen analysis

Answer 50

True. Water vapour affects the accuracy of many gas analysers including the paramagnetic gas analyser. The water vapour can also coat the internal mechanism.

Question 51

The following are true of viscosity: Established turbulent flow is independent of viscosity

Answer 51

True. In contrast to laminar flow and transitional flow (at the Reynolds number), viscosity changes do not affect established turbulent flow.

Question 52

The following are true of viscosity: Viscosity of blood increases with plasma protein concentration

Answer 52

True. Plasma protein concentration and haematocrit are the two key determinants of blood viscosity. Pathological increases in plasma proteins (such as seen in multiple myeloma) cause a hyperviscosity syndrome.

Question 53

The following are true of viscosity: Increased viscosity reduces blood flow

Answer 53

True. The Hagen-Poiseuille equation states that laminar fluid flow exhibits a reciprocal relationship with viscosity.

Question 54

The following are true of viscosity: Low temperature raises blood viscosity

Answer 54

True. This relationship is true of most liquids.

Question 55

The following are true of viscosity: Helium improves gas flow through an orifice by reducing viscosity

Answer 55

False. It is the density of helium that is most important.

Question 56

The following are true of manometers: 7.5 mm mercury is equivalent to 10.2 cm water

Answer 56

True. 1 kPa = 1000 Nm2, 0.01 Bar, 0.01 atmospheres, 7.5mm Hg and 10.2 cm H2O

Question 57

The following are true of manometers: 1 kPa is equal to a pressure of 7.5 mm mercury

Answer 57

True. 1 kPa = 1000 Nm2, 0.01 Bar, 0.01 atmospheres, 7.5mm Hg and 10.2 cm H2O

Question 58

The following are true of manometers: The top of a mercury manometer is closed to prevent contamination and spillage

Answer 58

False. It is essential that the top be open to allow pressure measurement relative to a constant atmospheric pressure. A manometer therefore measures gauge pressure.

Question 59

The following are true of manometers: A mercury barometer used to measure atmospheric pressure is sealed with a vacuum above the surface of the liquid

Answer 59

True. Compared to a manometer, a barometer specifically measures atmospheric pressure. Therefore, the top is closed to allow generation of a Torricellian vacuum. This allows absolute ambient pressure to be measured by the height of the mercury column.

Question 60

The following are true of manometers: Aneroid gauges do not contain liquid

Answer 60

True. The word 'aneroid' means 'no liquid.

Question 61

Measurement of peak expiratory flow rate: Reveals a normal diurnal variation of less than 10%

Answer 61

True. PEFR shows a nocturnal and early morning dip of up to 10%. A diurnal variation of 20% and above has been suggested as a useful indicator of asthmatic tendency.

Question 62

Measurement of peak expiratory flow rate: Is made ideally using a Vitalograph

Answer 62

False. A peak flow meter is more appropriate. A Vitalograph could be used in theory, but is bulky and would require subsequent analysis of its graphical output.

Question 63

Measurement of peak expiratory flow rate: With a Wright's peak flow meter uses the principle of a constant orifice with a variable pressure drop

Answer 63

False. It is a variable orifice device.

Question 64

Measurement of peak expiratory flow rate: Can be achieved using a'rapid' capnograph

Answer 64

False. A rapid capnograph only measures partial pressure of carbon dioxide against time and not gas flow or volume. In any event, the physiological dead space volume of expiration would not be detected

Question 65

Measurement of peak expiratory flow rate: Produces a reading which is normally 450 - 650 L min in the adult

Answer 65

True.

Question 66

Transducers: Convert one form of energy into another

Answer 66

True. This is the definition of a transducer.

Question 67

Transducers: Amplify the original signal

Answer 67

False. Their only function is to convert one form of energy to another. They cannot therefore increase it. To amplify a signal, a separate amplification system is required.

Question 68

Transducers: Can be active or passive

Answer 68

True. Active transducers generate electric current or voltage directly in response to environmental stimulation. (For example thermocouples and piezoelectric accelerometers.) Passive transducers produce a change in a passive electrical quantity, such as capacitance, resistance, or inductance, as a result of stimulation. (For example strain gauges, resistance temperature detectors and thermistors.)

Question 69

Transducers: Display a physiological event on an oscilloscope

Answer 69

False. Their only function is to convert one form of energy to another. They cannot therefore increase it. To amplify a signal, a separate amplification system is required.

Question 70

Transducers: Are used in the measurement of body temperature

Answer 70

True.

Question 71

The following are true of the measurement of body fluid volumes: Total blood volume can be measured directly using inulin

Answer 71

False. Inulin is used to measure ECF volume (as well as GFR).

Question 72

The following are true of the measurement of body fluid volumes: Extracellular fluid volume is measured using deuterium oxide or tritium

Answer 72

False. Deuterium oxide or tritium are isotopes of water, so can be used to measure total body water; ECF volume can be subtracted from this to give ICF volume.

Question 73

The following are true of the measurement of body fluid volumes: Intracellular fluid volume is measured indirectly from extracellular volume and total body water

Answer 73

True. IF volume cannot be measured directly, so must be inferred from extracellular and total body water.

Question 74

The following are true of the measurement of body fluid volumes: Plasma volume is measured with radio-iodinated albumin

Answer 74

True. Albumin is a large molecule which stays in plasma.

Question 75

The following are true of the measurement of body fluid volumes: Total red cell volume is measured with chromium-labelled red cells

Answer 75

True. 51Cr is an isotope that can be used to tag RBCs; thereby it can be used to calculate RBC volume.

Question 76

Anaesthetic gas cylinders: Are made of galvanised steel

Answer 76

False. Steel alloy cylinders are made of either manganese molybdenum steel, chromium molybdenum steel or nickel chromium molybdenum steel.

Question 77

Anaesthetic gas cylinders: For nitrous oxide contain it as a liquid

Answer 77

True. Nitrous oxide is stored in cylinders below its critical temperature, so is a vapour in equilibrium with its liquid.

Question 78

Anaesthetic gas cylinders: Filling ratio is the volume of the cylinder contents divided by the volume of water the cylinder could hold

Answer 78

False. Filling ratio is the weight of the cylinder contents divided by the weight of water it could hold.

Question 79

Anaesthetic gas cylinders: Filling ratio for nitrous oxide in the UK is 0.9

Answer 79

False. The ratio in UK is 0.75.

Question 80

Anaesthetic gas cylinders: May cool if gas flow rates are high

Answer 80

True. Adiabatic expansion of the gas being released at high flow rate will result in the gas cooling and therefore the cylinder will cool as well.

Question 81

In a well designed clinical study: A power of 50% is satisfactory

Answer 81

False. The power of a trial is the probability of avoiding a type Il statistical error (when the null hypothesis is incorrectly accepted). A power of 80% is required in a well designed trial.

Question 82

In a well designed clinical study: Double blinding ensures only the investigators are aware of the nature of the treatment

Answer 82

False. Double blinding means both investigators and participants are unaware of the nature of the treatment.

Question 83

In a well designed clinical study: A pilot study can predict the number of patients required

Answer 83

True. Pilot studies are used for this purpose before committing to the expense of a larger trial.

Question 84

In a well designed clinical study: Confidence intervals in each group are large

Answer 84

False. A wide confidence interval means that there is less confidence that a variable under study lies within a well defined range; a well designed trial will therefore possess narrow confidence intervals.

Question 85

In a well designed clinical study: A Chi Squared test can compare the sex distribution

Answer 85

True. The Chi Squared test is designed to test the difference between expected and observed observations and therefore lends itself to testing differences in sex distribution in a well designed trial.

Question 86

The standard deviation of a sample from a normally distributed characteristic in a population: Describes the degree of bias in choosing the sample

Answer 86

False. Standard deviation (SD) describes the scatter in the observations around their mean value, and says nothing about bias.

Question 87

The standard deviation of a sample from a normally distributed characteristic in a population: Determines the deviation about the mean which half the values might be expected to show

Answer 87

False.

Question 88

The standard deviation of a sample from a normally distributed characteristic in a population: Is the square root of the variance

Answer 88

True. This is the definition of SD.

Question 89

The standard deviation of a sample from a normally distributed characteristic in a population: Identifies limits of the deviation either side of the mean which include approximately two-thirds of the values

Answer 89

True. In a normally distributed population, 68.3 % of the values lie within 1 SD of the mean, 95.4% lie within 2 SD, and 99.7% lie within 3 SD of the mean.

Question 90

The standard deviation of a sample from a normally distributed characteristic in a population: Is greater than the standard error of the mean

Answer 90

True. The SEM is the SD/(number in sample), so SD > SEM.

Question 91

For the eight observations: 0,1,1, 1,2,4,5, 10: The range is 1 to 10

Answer 91

False. The range is 0 to 10.

Question 92

For the eight observations: 0,1,1, 1,2,4,5, 10: The standard deviation is a good measure of dispersion

Answer 92

False. This is clearly an asymmetric distribution skewed towards lower values.

Question 93

For the eight observations: 0,1,1, 1,2,4,5, 10: The median is 1.5

Answer 93

True. As there are an even number of observations, the median (the middlemost value) is the average of the two either side of the hypothetical middle value.

Question 94

For the eight observations: 0,1,1, 1,2,4,5, 10: The distribution is skewed

Answer 94

True. The distribution is positively skewed.

Question 95

For the eight observations: 0,1,1, 1,2,4,5, 10: The distribution is bimodal

Answer 95

False. The most frequent observation in this sample is 1 (three observations), all the other values occur once only; the sample is therefore a skewed, unimodal set, not bimodal.

Question 96

The following are true of electrical safety: Skin impedance is increased if faulty apparatus is touched with wet hands

Answer 96

False. Wetting the skin reduces its electrical impedance and increases the risk of shock.

Question 97

The following are true of electrical safety: Electrical shock is not a risk with potentials below 24V AC or 50V DC

Answer 97

False. Although 24 V AC or 50 V DC are the upper values in Class 3 (low voltage) electrical equipment, and macroshock is unlikely, it is not impossible and does not preclude microshock.

Question 98

The following are true of electrical safety: The modern diathermy return plate is not connected directly to earth

Answer 98

True. The principle of electrical safety is to prevent leakage currents to earth. The diathermy plate could form an electrical pathway to earth for a leakage current from any circuit with a patient attachment, not just the diathermy circuit. So modern thinking precludes earthing.

Question 99

The following are true of electrical safety: Microshock can cause ventricular fibrillation via an intracardiac catheter with current of 150 microamps

Answer 99

True. Microshock, which is shock from an electrical contact placed within the body, can cause ventricular fibrillation at currents above 100 microamps.

Question 100

The following are true of electrical safety: Leakage currents may be caused by voltages induced in other circuits by alternating mains current

Answer 100

True. There are a number of causes of leakage current. All current carrying conductors have an associated magnetic field; a changing magnetic field from an alternating current induces a voltage in neighbouring conductors, which may be the cause of an unintended leakage current.