Primary FRCA Course Measurement and Monitoring Exam Prep Questions

Question 1

In pulse oximetry:

The SpO2 is determined by the absorbance of light of wavelengths 660nm and 940nm

Answer 1

True. Pulse oximetry relies on measuring the relative absorbance at two wavelengths (660nm and 940nm). Reduced haemoglobin has greater absorbance at 660nm and oxyhaemoglobin greater at 940nm. The ratio is the determined and the SpO2 is then calculated

Question 2

In pulse oximetry:

Methaemoglobinaemia causes the SpO2 to approach 85%

Answer 2

True. Carboxyhaemoglobin causes an increase in SpO2 equal to its concentration, but methaemoglobin absorbs light equally at both 660nm and 940nm so the saturation tends towards a value of 85%

Question 3

In pulse oximetry:

Oxyhaemoglobin absorbs better at the longer wavelength

Answer 3

True. Pulse oximetry relies on measuring the relative absorbance at two wavelengths (660nm and 940nm). Reduced haemoglobin has greater absorbance at 660nm and oxyhaemoglobin greater at 940nm. The ratio is the determined and the SpO2 is then calculated

Question 4

In pulse oximetry:

Fetal haemoglobin gives an inaccurately high reading of saturation

Answer 4

False. Fetal haemoglobin does not affect the accuracy of pulse oximetry

Question 5

In pulse oximetry:

The pulse oximeter is less accurate at low rather than high saturations

Answer 5

True. The monitor is accurate to within 3% at values of over 70%, but less accurate as the saturation falls

Question 6

Regarding pulse oximetry:

The arterial a.c (pulsatile) component of the signal is approximately 20% of the total absorption

Answer 6

False. The pulsatile component is typically 2% of the total absorption.

Question 7

Regarding pulse oximetry:

Functional saturation is defined as the ratio of oxyhaemoglobin to oxyhaemoglobin plus reduced haemoglobin

Answer 7

True. Functional saturation is the ratio of O2HB to (O2Hb + Hb), it is Fractional saturation that includes other haemoglobins.

Question 8

Regarding pulse oximetry:

Beer’s law relates the intensity of transmitted light to the path length

Answer 8

False. Beer’s law relates the absorption of transmitted light to the concentration of the substance whereas Lamberts law relates it to path length.

Question 9

Regarding pulse oximetry:

Infrared light is only absorbed by small molecules with symmetric bonds

Answer 9

False. Infrared light is absorbed by small molecules with asymmetric bonds so that vibration can occur.

Question 10

Regarding pulse oximetry:

Motion artefacts produces a high a.c. to d.c. signal ratio

Answer 10

True. Motion will produce an increase in a.c. components however this is noise and therefore the signal to noise ratio will be lower

Question 11

Causes of inaccuracies on pulse oximetry include:

Methaemoglobinaemia

Answer 11

True. MetHb, hypothermia (causing vasoconstriction) and extraneous lighting can all affect pulse oximetry accuracy.

Question 12

Causes of inaccuracies on pulse oximetry include:

Fetal haemoglobin

Answer 12

False. Fetal haemoglobin does not have a significant effect.

Question 13

Causes of inaccuracies on pulse oximetry include:

Hypothermia

Answer 13

True. MetHb, hypothermia (causing vasoconstriction) and extraneous lighting can all affect pulse oximetry accuracy.

Question 14

Causes of inaccuracies on pulse oximetry include:

Blue nail polish

Answer 14

True. Blue nail varnish absorbs red light and can affect readings. Similarly the use of blue dyes for sentinel node biopsy can lead to reduction in recorded oxygen saturation using a pulse oximeter

Question 15

Causes of inaccuracies on pulse oximetry include:

Extraneous lighting

Answer 15

True. MetHb, hypothermia (causing vasoconstriction) and extraneous lighting can all affect pulse oximetry accuracy.

Question 16

Concerning the measurement of oxygen:

A Clark electrode requires a polarising voltage

Answer 16

True. The Clark electrode is a polarographic electrode and needs a polarising voltage.

Question 17

Concerning the measurement of oxygen:

Fuel cells can be affected by the presence of nitrous oxide

Answer 17

True. Some fuel cells are affected by N2O.

Question 18

Concerning the measurement of oxygen:

A paramagnetic analyser has a slower response time than a Clark electrode

Answer 18

False. Modern paramagnetic analysers have a fast response time.

Question 19

Concerning the measurement of oxygen:

A polarographic technique is used in normal blood gas analysers

Answer 19

True. Oxygen is measured by a polarographic technique in most blood gas analysers.

Question 20

Concerning the measurement of oxygen:

Oxygen saturation is directly measured using a co-oximeter

Answer 20

False. A CO-oximeter measures the concentrations of different haemoglobins and calculates the oxygen saturation from the relevant percentages.

Question 21

The following are directly measured in a standard blood gas analyser:

pH

Answer 21

False!!? A blood gas analyser directly measures hydrogen ion concentration using a glass electrode. pH is calculated mathematically as the negative Log of the hydrogen ion concentration and therefore not directly measured! Small but important point if asked in the exam.

Question 22

The following are directly measured in a standard blood gas analyser:

Bicarbonate concentration

Answer 22

A blood gas analyser directly measures hydrogen ion concentration using a glass electrode, the tension of oxygen using a polarographic electrode and carbon dioxide indirectly through a modification of the glass electrode. Bicarbonate is extrapolated using the HH equation.

Question 23

The following are directly measured in a standard blood gas analyser:

Oxygen tension

Answer 23

True. A blood gas analyser directly measures hydrogen ion concentration using a glass electrode, the tension of oxygen using a polarographic electrode and carbon dioxide indirectly through a modification of the glass electrode.

Question 24

The following are directly measured in a standard blood gas analyser:

Partial pressure of carbon dioxide

Answer 24

False. A blood gas analyser directly measures hydrogen ion concentration using a glass electrode, the tension of oxygen using a polarographic electrode, and carbon dioxide indirectly through a modification of the glass electrode. Partial pressures are derived by measuring the atmospheric pressure.

Question 25

The following are directly measured in a standard blood gas analyser: Oxygen saturation

Answer 25

False. A blood gas analyser directly measures hydrogen ion concentration using a glass electrode, the tension of oxygen using a polarographic electrode, and carbon dioxide indirectly through a modification of the glass electrode. Oxygen saturation may be derived but is not directly measured

Question 26

Arterial blood gas samples: Storage at room temperature causes a rise in pH

Answer 26

False. Blood gas samples become acidotic with time so the pH falls.

Question 27

Arterial blood gas samples: A hypothermic patient will have an inaccurately high pO2 if temperature-correction is not employed

Answer 27

True. If temperature-correction is not applied then hypothermic patients will have an inaccurately high PO2 reading.

Question 28

Arterial blood gas samples: Air bubbles in the sample may lead to a fall in the pCO2

Answer 28

True. Air bubbles contain no CO2 so will reduce the reading of pCO2.

Question 29

Arterial blood gas samples: Excessive heparin will cause an inaccurately high pH

Answer 29

False. Heparin is acidic so will reduce the pH.

Question 30

Arterial blood gas samples: Storage at room temperature causes a fall in pO2

Answer 30

True. At room temperature white cells metabolise oxygen and pO2 falls.

Question 31

The oxygen electrode in a blood gas analyser: Incorporates on a lead anode

Answer 31

False. The anode is typically silver and the cathode platinum, the electrolyte solution is a potassium chloride solution.

Question 32

The oxygen electrode in a blood gas analyser: The cathode is usually platinum

Answer 32

True. The anode is typically silver and the cathode platinum, the electrolyte solution is a potassium chloride solution.

Question 33

The oxygen electrode in a blood gas analyser: Potassium hydroxide is the usual electrolyte in the electrode

Answer 33

False. The anode is typically silver and the cathode platinum, the electrolyte solution is a potassium chloride solution.

Question 34

The oxygen electrode in a blood gas analyser: Current flow depends on oxygen tension at the cathode

Answer 34

True. Current flow depends on the oxygen tension at the cathode. The more oxygen there is the greater the current (this is the principle of an amperometric sensor). At the cathode a reductive reaction occurs and oxygen is consumed with the gain of electrons to form hydroxide ions.

Question 35

The oxygen electrode in a blood gas analyser: Is of the fuel cell type

Answer 35

False. Fuel cells are not used in blood gas analysers. The polarographic (Clark) Electrode is used in blood gas analysers.

Question 36

The fuel cell: Contains a lead anode

Answer 36

True. A fuel cell contain a lead anode and gold mesh cathode.

Question 37

The fuel cell: Has a faster response time than a polarographic electrode

Answer 37

False. They both have relatively slow response time as it is they are electrochemical processes.

Question 38

The fuel cell: Is not affected by temperature

Answer 38

False. It is affected by temperature as a chemical reaction takes place.

Question 39

The fuel cell: Nitrous oxide in the gas mixture reacts with the anode to produce nitrogen

Answer 39

True. Nitrous oxide is broken down to nitrogen at the anode.

Question 40

The fuel cell: Is used to measure oxygen tension in a blood gas analyser

Answer 40

False. Typically a Clark polarographic electrode is used in a blood gas analyser.

Question 41

Concerning the Clark PO2 electrode: Is composed of a platinum cathode and a gold anode

Answer 41

False. The Clark electrode has a platinum cathode and SILVER anode. A fuel cell has gold cathode.

Question 42

Concerning the Clark PO2 electrode: An oxygen consuming electrochemical reaction takes place at the anode

Answer 42

False. The oxygen consuming reaction takes place at the cathode where there is gain of electrons (reduction).

Question 43

Concerning the Clark PO2 electrode: It can be used to measure oxygen partial pressure in gases and liquids

Answer 43

True. A Clark electrode can be used in both gases and liquids.

Question 44

Concerning the Clark PO2 electrode: It requires a voltage of 0.6 V to be applied between its electrodes

Answer 44

True. Typically a polarising voltage of 0.6 V is used.

Question 45

Concerning the Clark PO2 electrode: It is sensitive to changes in temperature

Answer 45

True. As with all electrochemical electrodes it is sensitive to changes in temperature.

Question 46

The Severinghaus carbon dioxide electrode: Incorporates KCL and NaHCO3 in the electrolyte solution

Answer 46

True. KCl and NaHCO3 are in the electrolyte solution

Question 47

The Severinghaus carbon dioxide electrode: Directly measures the PaCO2

Answer 47

False. The electrode is a modification of the glass electrode and measures the hydrogen ion concentration in the bicarbonate solution. It is therefore an indirect measure of PaCO2.

Question 48

The Severinghaus carbon dioxide electrode: Incorporates hydrogen ion sensitive glass

Answer 48

True. The pH electrode incorporates hydrogen ion sensitive glass which generates a potential difference across the glass in the presence of hydrogen ions.

Question 49

The Severinghaus carbon dioxide electrode: Incorporates a platinum wire cathode

Answer 49

False. It is the oxygen electrode that has a platinum cathode.

Question 50

The Severinghaus carbon dioxide electrode: Is affected by temperature

Answer 50

True. All electrochemical electrodes are affected by temperature

Question 51

Recognised methods of measuring anaesthetic vapour concentration include: Raman scattering

Answer 51

True.

Question 52

Recognised methods of measuring anaesthetic vapour concentration include: Paramagnetism

Answer 52

False. Paramagnetism is used for oxygen analysis as oxygen does not absorb infrared light

Question 53

Recognised methods of measuring anaesthetic vapour concentration include: Ultraviolet absorption

Answer 53

True. UV absorption is a recognised method of historical interest only.

Question 54

Recognised methods of measuring anaesthetic vapour concentration include: Mass spectrometry

Answer 54

True.

Question 55

Recognised methods of measuring anaesthetic vapour concentration include: Photoacoustic spectrophotometry

Answer 55

True. The main method of measuring anaesthetic vapour concentration is Infrared Absorption Spectrophotometry. Photoacoustic spectrometry is similar but measures sound generated rather that light absorbed.

Question 56

The following can be used to measure carbon dioxide in expired gases (capnography): Clark polarographic electrode

Answer 56

False. Capnography is usually undertaken using infrared absorption spectrophotometry. Mass spectrometry and Raman scattering can also be used. Paramagnetic analysers and the Clark electrode measure oxygen

Question 57

The following can be used to measure carbon dioxide in expired gases (capnography): Paramagnetic analyser

Answer 57

False. Capnography is usually undertaken using infrared absorption spectrophotometry. Mass spectrometry and Raman scattering can also be used. Paramagnetic analysers and the Clark electrode measure oxygen

Question 58

The following can be used to measure carbon dioxide in expired gases (capnography): Infrared absorption spectrometry

Answer 58

True. Capnography is usually undertaken using infrared absorption spectrophotometry. Mass spectrometry and Raman scattering can also be used. Paramagnetic analysers and the Clark electrode measure oxygen

Question 59

The following can be used to measure carbon dioxide in expired gases (capnography): Mass spectrometry

Answer 59

True. Capnography is usually undertaken using infrared absorption spectrophotometry. Mass spectrometry and Raman scattering can also be used. Paramagnetic analysers and the Clark electrode measure oxygen

Question 60

The following can be used to measure carbon dioxide in expired gases (capnography): Raman analyser

Answer 60

True. Capnography is usually undertaken using infrared absorption spectrophotometry. Mass spectrometry and Raman scattering can also be used. Paramagnetic analysers and the Clark electrode measure oxygen

Question 61

The following have infrared absorption spectra which overlap with that of carbon dioxide: Water vapour

Answer 61

True. Water vapour, sevoflurane and nitrous oxide all have infrared absorption spectra which overlap with that of CO2.

Question 62

The following have infrared absorption spectra which overlap with that of carbon dioxide: Sevoflurane

Answer 62

True. Water vapour, sevoflurane and nitrous oxide all have infrared absorption spectra which overlap with that of CO2.

Question 63

The following have infrared absorption spectra which overlap with that of carbon dioxide: Nitrous oxide

Answer 63

True. Water vapour, sevoflurane and nitrous oxide all have infrared absorption spectra which overlap with that of CO2.

Question 64

The following have infrared absorption spectra which overlap with that of carbon dioxide: Nitrogen

Answer 64

False. Nitrogen does not absorb infrared light as it only has symmetric bonds

Question 65

The following have infrared absorption spectra which overlap with that of carbon dioxide: Helium

Answer 65

False. Helium does not absorb infrared light as it only has symmetric bonds

Question 66

Concerning the measurement of expired carbon dioxide using the infrared absorption technique: The wavelength of infrared light used is 4.3 micrometres

Answer 66

True.

Question 67

Concerning the measurement of expired carbon dioxide using the infrared absorption technique: The absorption of infrared light by carbon dioxide is based on the Beer-Lambert law

Answer 67

True. Absorption follows the Beer-Lambert law with absorption being dependant on concentration and path length.

Question 68

Concerning the measurement of expired carbon dioxide using the infrared absorption technique: The windows on the sample chamber are made of lead crystal glass

Answer 68

False. The windows are made of a material that is transparent to infrared, lead crystal glass is not.

Question 69

Concerning the measurement of expired carbon dioxide using the infrared absorption technique: Nitrous oxide interferes with infrared absorption by carbon dioxide

Answer 69

True. N2O, and volatile agents interfere with the measurement due to collision broadening which is a physical interaction between the different molecules.

Question 70

Concerning the measurement of expired carbon dioxide using the infrared absorption technique: Oxygen interferes with infrared absorption by carbon dioxide

Answer 70

True. Oxygen can interfere with the measurement though it does not absorb infrared light

Question 71

Concerning spectrophotometric absorption spectra of reduced and oxygenated haemoglobin: At the isosbestic point, the absorption coefficient is the same

Answer 71

True. The isobestic, or as it more properly written, isosbestic point for oxy and deoxyhaemaglobin is approximately 805nm and is the point at which both molecules absorb equally.

Question 72

Concerning spectrophotometric absorption spectra of reduced and oxygenated haemoglobin: The isosbestic point occurs at a wavelength around 650 nm

Answer 72

False. The isobestic, or as it more properly written, isosbestic point for oxy and deoxyhaemaglobin is approximately 805nm and is the point at which both molecules absorb equally.

Question 73

Concerning spectrophotometric absorption spectra of reduced and oxygenated haemoglobin: The amount of oxygenated haemoglobin is directly proportional to the shift in the isosbestic point

Answer 73

False. The isosbestic does not shift with respect to differing proportions of oxy and deoxyhaemoglobin.

Question 74

Concerning spectrophotometric absorption spectra of reduced and oxygenated haemoglobin: The maximum difference in the absorption of the two forms of haemoglobin occurs at a wavelength around 940 nm

Answer 74

False. The maximum difference in the absorption of the two forms of haemoglobin occurs at a wavelength of about 650 nm.

Question 75

Concerning spectrophotometric absorption spectra of reduced and oxygenated haemoglobin: The pulse oximeter uses the difference between the absorption spectra of the two forms of Hb to quantify their relative concentrations

Answer 75

True.

Question 76

Refractometers: Are capable of measuring vapour concentration in gas mixture

Answer 76

True. Refractometers are typically used to measure vapour concentrations in gas mixtures by measuring the bending of light waves due to the change in gas composition.

Question 77

Refractometers: Require calibration

Answer 77

True.

Question 78

Refractometers: Directly measure the vapour concentration

Answer 78

False. They measure vapour concentration INDIRECTLY.

Question 79

Refractometers: Are not influenced by water vapour

Answer 79

False. They are influenced by water vapour.

Question 80

Refractometers: Are used to calibrate vaporisers

Answer 80

True.

Question 81

Blood-gas analysis: The base excess is the amount of strong acid required to return the pH of 1 litre of blood to 7.40 at a PCO2 of 5.3 kPa and 37°C

Answer 81

True. Base excess is used to assess the metabolic component of the blood-gas analysis.

Question 82

Blood-gas analysis: Too much heparinised saline tends to cause a falsely low reading of the PCO2

Answer 82

True. Errors can occur due to excessive heparin either due to the dilutional effect of excessive saline (low pCO2 and low pO2, though the pH is little effected), or due to the heparin itself (high potassium measurement)

Question 83

Blood-gas analysis: Too much heparin tends to cause a falsely low reading of potassium concentration

Answer 83

False. Errors can occur due to excessive heparin either due to the dilutional effect of excessive saline (low pCO2 and low pO2, though the pH is little effected), or due to the heparin itself (high potassium measurement).

Question 84

Blood-gas analysis: A Clark electrode requires a battery

Answer 84

True. It is the fuel cell that does not

Question 85

Blood-gas analysis: Prolonged storage at 4°C may lead to a falsely low value for PO2

Answer 85

True. Prolonged storage even at 4°C can lead to either a falsely low reading of pO2 (due to ongoing metabolism in white blood cells) or a falsely high reading (due to bubbles dissolving).

Question 86

The following statements are correct: Visible light has a wavelength between 400 and 700 nanometers

Answer 86

True. Visible light is between 400 (Blue) and 700 (Red) nm.

Question 87

The following statements are correct: Carbon dioxide has a peak absorption at 4.3 micrometers

Answer 87

True. CO2 has an absorption peak at 4.3 micrometres.

Question 88

The following statements are correct: 3.3 micrometers is the common absorption peak for volatile anaesthetic agents

Answer 88

True. Volatile agents have absorption peaks close to 3.3 micrometres.

Question 89

The following statements are correct: Methane interferes with gas analysis in the 9-11 micrometer band

Answer 89

False. Methane absorbs in the 3-4 micrometre range and can build up in circle breathing systems. There is a second volatile agent peak at 9-11 micrometers that is not affected by methane.

Question 90

The following statements are correct: Collision broadening alters the wavelengths at which infrared absorption by carbon dioxide takes place

Answer 90

True. Collision broadening widens the range of wavelengths absorbed by CO2.

Question 91

Concerning mass spectrometry: The analysing chamber operated at atmospheric pressure

Answer 91

False. The chamber in a mass spectrometer operates at near vacuum pressures and requires a pump to maintain this pressure.

Question 92

Concerning mass spectrometry: The ions are accelerated by an anode plate

Answer 92

False. The ions are accelerated by a cathode plate.

Question 93

Concerning mass spectrometry: In a quadruple mass spectrometer there are two large electromagnets

Answer 93

False. A quadrupole mass spectrometer has 4 electromagnets that produce the ion gate.

Question 94

Concerning mass spectrometry: The sample from a mass spectrometer can be returned to a circle system to allow low flow anaesthesia

Answer 94

False. Samples from a mass spectrometer are ionised and cannot be returned to the breathing circuit.

Question 95

Concerning mass spectrometry: Mass spectrometry is less accurate than infrared absorption spectrophotometry

Answer 95

False. Mass spectrometers the gold standard of gas analysers.

Question 96

The following statements are correct: Fuel cells are suitable for breath to breath analysis of oxygen concentration

Answer 96

False. Both fuel cells and the polarographic electrode are not suitable for breath to breath analysis due to their slow response time

Question 97

The following statements are correct: Unpaired electrons are responsible for oxygen's paramagnetic property

Answer 97

True. Oxygen and Nitric Oxide are paramagnetic due to unpaired electrons in their outer rings

Question 98

The following statements are correct: Damping coefficient is inversely proportional to the amplitude ratio in invasive arterial pressure measurement

Answer 98

True. A high amplitude ratio suggests little damping and therefore a low damping coefficient

Question 99

The following statements are correct: The natural frequency of a mass-string dynamic oscillator is directly proportional to its mass

Answer 99

False. It is inversely proportional to the square root of the mass

Question 100

The following statements are correct: Fourier Transformation is a mathematical operation that deconstructs a complex signal into its constituent frequencies

Answer 100

True. This is the definition of Fourier Transformation.