Part 4: Physics & Equipment Flashcards

Question

List the advantages and disadvantages of **side stream gas analysers**.

Answer 1

**ADVANTAGES** * Lightweight * Less risk of disconnection due to weight **DISADVANTAGES** * Sampling delay (3-5 seconds) * Narrow tube can get blocked * Requires scavenging

Answer 2

* Type B * Type BF * Type CF ## Footnote **Type B**: touches skin but does not penetrate (e.g. ECG) **Type BF**: part that touches the patient is electrically isolated from the rest of the device (e.g. thermometer) **Type CF**: for equipment that touches the heart or is inserted into the body (e.g. pacing wires). < 10 µA leakage current NOTE: B - body, C - cardiac, F - floating

Answer 3

**Cutting**: sine wave **Coagulation**: pulsed sine wave

Answer 4

60 cm H₂O

Answer 5

* Allows switching between A, D and E by altering the lever position * A (lever up) for spontaneous and E (lever down) for controlled * Reservoir bag can be attached to end of T-piece to make it a D

Answer 6

25-27 G pencil-point needle

Answer 7

Minute volume and tidal volume ## Footnote NOTE: under-reads at low flows, over-reads at high flows, condensation can make pointer get stuck

Answer 8

* 1 cm = 1 mV * 25 mm/sec * Small Square: 0.04 s * Big Square: 0.2 s

Answer 9

Metal oxide beads

Answer 10

Spectrophotometer that uses four different wavelengths for haemoglobin, oxyhaemoglobin, carboxyhaemoglobin and methaemoglobin. ## Footnote Used in blood gas machines but not suitable for continuous monitoring

Answer 11

10-20 seconds

Answer 12

* **Pink**: 15 mm (3-39 kg) * **Blue**: 25 mm (39+ kg) * **Yellow**: 45 mm (excess soft tissue) ## Footnote NOTE: Usually 14 or 16 G is used.

Answer 13

Inner: 7 mm Outer: 22 mm ## Footnote NOTE: Usual length of a Bain circuit is 1.8 m.

Answer 14

Measures pressure without using liquid. ## Footnote e.g. Bourdon, diaphragm, bellows NOTE: Bourdon gauge is only appropriate for higher pressures (multiples of atmospheric).

Answer 15

* **CD**: 460 L (standard for transfer) * **D**: 340 L * **E**: 680 L (anaesthetic machines) * **G**: 3400 L * **J**: 6800 L (cylinder manifolds)

Answer 16

70 mL/kg/min for controlled 100 mL/kg/min for spontaneous ventilation

Answer 17

* Air bubbles * Clots * Kinking * Stopcocks * Narrow, compliant, long tubing

Answer 18

Density of a substance divided by the density of a reference substance (water at 4 degrees)

Answer 19

30 L/min 4 bar Bypasses flowmeters and vaporisers

Answer 20

15 mm and 22 mm

Answer 21

Bonding all conductive parts and equipment with low-resistance connections to a common earth reference. ## Footnote Ensures there are no voltage differences so prevents current passing through a person.

Answer 22

* Na * K * Ca

Answer 23

30 times per second

Answer 24

* Convert AC to DC current (knowing as rectification). * May also be referred to as a rectifier.

Answer 25

* Low penetration rate * Effective bidirectionally * Small internal volume (hence, dead space) * Minimal resistance to gas flow * Effective when wet or dry * Disposable * Cheap * Transparent and lightweight

Answer 26

At a fixed volume, pressure and temperature are directly proportional.

Answer 27

At a fixed pressure, volume and temperature are directly proportional.

Answer 28

At a fixed temperature, the product of pressure and volume is constant (k=PV).

Answer 29

At a given temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of gas in equilibrium with the liquid.

Answer 30

Describes how the rate of a diffusion of a substance is inversely proportional to its molecular weight.

Answer 31

One coulomb is the amount of charge transported by a current of one ampere in one second. 1 C = 1 A x 1 s Equals: 6.25 × 10¹⁸ electrons

Answer 32

* **Resistance** describes the opposition to flow of direct current. * **Reactance** is opposition to alternating current. * **Impedance** is the sum of resistive and reactive components. ## Footnote NOTE: These are all measured in ohms.

Answer 33

**ZEROTH**: If two thermodynamic systems are in equilibrium with a third then they are also in equilibrium with each other. **FIRST**: Energy can neither be created or destroyed only converted from one form to another. **SECOND**: Entropy (i.e. a measure of unavailable energy) tends to increase with time. **THIRD**: As a system approaches absolute zero (-273.15ºC) all processes cease and entropy approaches a minimum.

Answer 34

* STEP 1: sodium deoxycholate haemolyses erythrocytes releasing Hb * STEP 2: sodium nitrite converts Hb to MetHb which then reacts with sodium azide to give azidemethaemoglobin * STEP 3: absorbance is measured at two wavelengths (570 nm and 880 nm). Degree of absorbance is relative to Hb concentration. * STEP 4: after each reading, photometer zeros itself and checks the intensity of the light source and photocell

Answer 35

Where a resistor and capacitor are placed in series as a circuit. It acts as a low pass filter i.e. allows frequencies below a certain value to pass.

Answer 36

Equal volumes of an ideal gas at standard temperature and pressure will contain an equal number of molecules, and that one mole of an ideal gas at standard temperature and pressure occupies 22.4 litres.

Answer 37

The point at which water exists in solid, liquid and gas phases at equilibrium 273.16 K and 611 Pa.

Answer 38

* 20: 17 g/m³ * 34: 34 g/m³ * 37: 44 g/m³

Answer 39

Has a natural frequency that is 10 times higher than the fundamental frequency.

Answer 40

* Consists of a semiconductor for which there is a non-linear relationship between resistance and temperature (in most cases, resistance decreases with temperature). * Cheap and small so can be used for invasive monitors (e.g. pulmonary artery flotation catheter). * Responds quickly to changes but are susceptible to calibration error.

Answer 41

As temperature increases, resistance through a thin piece of metal increases linearly. Slow response time and fragile.

Answer 42

They rely on the Seebeck (thermoelectric) effect. At the junction of two dissimilar metals, a voltage will be produced in proportion to the temperature difference between two such junctions where the temperature of one of the junctions is known. The response is nearly linear and passes through the origin as a temperature difference of zero produces zero output voltage. Multiple thermocouples in series produce a thermopile which will increase sensitivity.

Answer 43

At the bottom (low-flow), the space between the bobbin and wall is narrow. Gas flow is laminar and dependent on viscosity. At the top (high flows) the space between the bobbin and wall is wider. Gas flow is more turbulent and dependent on density. The pressure difference across the bobbin is constant at all points in the rotameter.

Answer 44

* **State Entropy**: calculated from low frequency range waves * **Response Entropy**: calculated from high frequency waves including EMG activity from frontalis muscle

Answer 45

* Flow is proportional to the radius squared * Flow is proportional to the square root of the pressure gradient * Flow is inversely proportional to the length and density of the fluid

Answer 46

* Heat energy lost * When a ferromagnetic material is placed in a magnetic field, it will become magnetised (O to A) * When the field is removed, it remains weakly magnetised (A to B) * Area within the loop is heat loss

Answer 47

Process of rendering an object free from all pathogenic organisms excluding bacterial spores.

Answer 48

Method of disinfection that uses temperatures of 70 °C for 30 minutes.

Answer 49

Measurement of total magnetic field passing through a given area. ## Footnote NOTE: When divided by the size of the area, it is called magnetic flux density.

Answer 50

* Magnetic Flux: Weber (Wb) * Magnetic Flux Density: 1 Tesla = 10,000 Gauss ## Footnote NOTE: 1 Tesla = 1 Wb/m²

Answer 51

Obstruction of the common gas outlet can cause rising pressure within the circuit that can transmit gases back into the anaesthetic machine causing damage and contamination. ## Footnote This valve opens at 35-40 kPa of pressure.

Answer 52

* 1 mA: tingle * 5 mA: pain * 15 mA: sustained muscle contraction * 50 mA: respiratory arrest * 100 mA: ventricular fibrillation * 1000 mA: extensive burns and charring

Answer 53

Z = \( \frac{d}{f \cdot a} \) ## Footnote Z = impedance d = distance between plates f = frequency of current a = area of plates

Answer 54

**Decontamination**: Removes contaminants to prevent infection; involves cleaning, disinfection, and sterilisation. **Disinfection**: Removes or kills all pathogenic organisms **except bacterial spores**. **Sterilisation**: Removes or kills all pathogenic organisms, **including bacterial spores.**

Answer 55

* Retrieval (via a low pressure suction) * Filter (150 µm) * Centrifuge * Disposal of waste * Wash and resuspension * Reinfusion (solution with haematocrit 60%)

Answer 56

When oxygen pressure falls below 200 kPa. ## Footnote NOTE: Alarm has a volume of 60 dB for 7 seconds.

Answer 57

Ambient air is filtered and pressurized to 137 kPa. It enters one of the parallel towers beside the mix tank. Air passes through a molecular sieve made from **zeolite**, attracting nitrogen while allowing oxygen to pass. A changeover switch directs gas to the second tower, while nitrogen is removed from the first tower using a vacuum.

Answer 58

c = f λ ## Footnote c = speed of light (m/s) f = frequency (Hz) λ = wavelength (m)

Answer 59

E = h f ## Footnote h is Planck’s constant

Answer 60

* **Monitoring**: 0.5 to 40 Hz * **Diagnostic**: 0.05 to 100 Hz

Answer 61

Absorbance (A) = log(I₀/I₁) = αlc ## Footnote α = extinction coefficient l = path length c = concentration

Answer 62

* Date of test * Test pressure * Chemical formula * Tare weight

Answer 63

* Consists of a silver tube filled with ether and a thermometer. * Air is bubbled through the ether causing a drop in temperature due to the latent heat of vaporisation. * Condensation forms on the silver tube at the dew point. The temperature at which this occurs can be used to calculate the relative humidity using look up tables.

Answer 64

590 and 805 nm

Answer 65

* Left-facing bevel: better view of tip * Murphy's eye: allows ventilation if tip obstructed * Magill curve: follows anatomy of upper airway * Low pressure, high volume cuff * Vocal cord guide

Answer 66

* 14G (orange) 270 ml/min. * 16G (grey) 180 ml/min. * 18G (green) 80 ml/min. * 20G (pink) 54 ml/min. * 22G (blue) 31 ml/min.

Answer 67

One single mark at the tip so that it may be identified on removal. They have 5 single markings at 1 cm intervals from 5-9 cm, a double marking at 10cm, 1cm intervals from 10-14cm, a triple marking at 15cm and then quadruple markings at 20cm.

Answer 68

Inductor One Henry is the inductance when one ampere flowing in a coil generates a magnetic field strength of one weber i.e. H = Wb/A.

Answer 69

* Water vapour content of expired gas * Inspiratory and expiratory flow rates (slower means more time that gas is in contact with HMEF material) * Volume of HMEF material (larger = more efficient) * Thermal conductivity (low conductivity maintains greater temperature difference between either side of the HMEF and enables more heat and moisture to be transferred)

Answer 70

In MRI, relaxation refers to the process by which net magnetisation returns to equilibrium after the radiofrequency (RF) pulse is turned off. This occurs through two mechanisms: * T1 relaxation (spin-lattice): the time taken for magnetisation to realign with the main magnetic field by releasing energy to surrounding tissue. * T2 relaxation (spin-spin): the time taken for protons to lose phase coherence with each other in the transverse plane. T1 reflects recovery of alignment; T2 reflects loss of synchrony. Both are negative exponential processes and vary by tissue type.

Answer 71

* Oxygen knob is always furthest to the left, is slightly larger and has a ridged texture * Colour coded (white) as per pipeline oxygen * Hypoxic guard (linking oxygen and nitrous oxide valves so that minimum deliverable oxygen concentration when nitrous is used is 25%)

Answer 72

'Left-sided' indicates the bronchus the tube enters. It has two openings: a proximal opening to the trachea above the carina and a distal opening in the left main bronchus. The proximal lumen is clear for the trachea, and the distal lumen is blue for the bronchus. * **Two-lung ventilation**: Inflate the tracheal cuff and connect the clear lumen to the breathing circuit. * **Right-lung ventilation**: Inflate both cuffs and connect the clear lumen (deflates the left lung). * **Left-lung ventilation**: Inflate both cuffs and connect the blue lumen.

Answer 73

* **Red**: halothane * **Purple**: isoflurane * **Yellow**: sevoflurane * **Blue**: desflurane * **Orange**: enflurane

Answer 74

Frequency below which 95% of brain wave activity occurs. Provides a single value indicating the dominant frequency range in the EEG signal.

Answer 75

* The system is unable to prevent oscillations in response to a step change. * The new value is reached quickly but the system oscillates before eventually settling at the new value. * Typical damping coefficient is 0-0.3

Answer 76

* Characterised by a blunted response to a step change. * A long time is taken to reach the new value but there is no overshoot. * The damping coefficient is >1.

Answer 77

* Has a damping coefficient of 1. * This provides the quickest attainment of the new input value with no overshoot. * This is still slower than optimal damping.

Answer 78

* This is the best combination of rapid response to a stepped change in input and minimal overshoot. * There are no more than 2 oscillations prior to attaining the new value. * Has a damping coefficient of 0.64.

Answer 79

Up to 200 mL/min Extraction pressure is -3 to -6 kPa

Answer 80

* Particles occupy NO VOLUME * Experience NO INTERMOLECULAR FORCES * Collisions are PERFECTLY ELASTIC and they obey the ideal gas law under all conditions

Answer 81

Lead zirconate titanate | (PZT)

Answer 82

C = Q/V ## Footnote C: capacitance Q: charge V: voltage

Answer 83

PARALLEL: C1 + C2 + Cn SERIES: 1/Cₜₒₜₐₗ = 1/C₁ + 1/C₂ + ... + 1/Cₙ

Answer 84

C = ε × A/d Capacitance increases with larger plate area (A), smaller distance between plates (d), and higher permittivity (ε) of the dielectric material

Answer 85

* Oxidiser (oxygen or nitrous oxide) * Fuel source (such as surgical drapes or alcohol-based preparations) * Ignition (like electrosurgical units or laser beams)

Answer 86

Measures blood pressure through the mechanical expansion and contraction of bellows, which moves a pointer across a calibrated scale to indicate pressure changes.

Answer 87

Freezing point osmometer ## Footnote Determines osmolality by measuring the freezing point depression, which correlates with solute concentration.

Answer 88

Coherence between high- and low-frequency EEG components. This indicates consistency of phase relationships across EEG frequencies. In deeper anaesthesia, EEG signals synchronize, increasing coherence (lowering BIS number).

Answer 89

200 mL/kg/min

Answer 90

* Improved humidity and temperature of inspired gases (as it has passed through the respiratory tract). * Minimises consumption of volatile agents.

Answer 91

The electric force between two charges is inversely proportional to the square of the distance between them.

Answer 92

Surgical instrument used to freeze and destroy tissue. Works by rapidly cooling its tip using compressed gases (like nitrous oxide or carbon dioxide), which expand and cool (Joule-Thomson effect), freezing adjacent tissue on contact.

Answer 93

**Ostwald**: The ratio of the volume of a gas dissolved in a liquid to the volume of the gas at the same temperature and pressure. Dimensionless figure that is more commonly used. **Bunsen**: The volume of a gas, corrected to 0 °C and 1 atm, that dissolves in a unit volume of liquid at a given temperature.

Answer 94

200 micrometres

Answer 95

Pass through a 4-mesh (4 openings per inch) Retained by 8-mesh (8 openings per inch) This gives a granule size of 2.38 mm to 4.75 mm in diameter.

Answer 96

1. Step-up transformer increases 240 to 5000 V 2. Capacitor needs DC to charge so rectifier (diode) converts AC to DC 3. Switch charges and discharges capacitor 4. Inductor smooths the current delivered to the defibrillator pads

Answer 97

The partial vapour pressure of a component in a solution equals the vapour pressure of the pure component multiplied by its mole fraction in the solution. ## Footnote EXAMPLE In a 1:1 mole ratio mixture of ethanol (SVP 44 mmHg) and water (SVP 24 mmHg), the total vapour pressure = (0.5 × 44) + (0.5 × 24) = 34 mmHg.

Answer 98

In vs Out of Plane = NEEDLE Long vs Short Axis = Anatomy

Answer 99

Insulating material that, when placed in an electric field, becomes polarised, allowing it to support the field and store electrical energy without conducting current. ## Footnote Used in capacitors (e.g. ceramic)

Answer 100

**ETT**: 15 mm **Catheter Mount**: 22 mm

Answer 101

**E = 1/2 C V²** ## Footnote **E** = energy **C** = capacitance **V** = voltage This equation shows that energy storage increases with the square of the voltage applied.

Answer 102

HIGH USAGE (also cold weather): decrease in oxygen temperature and pressure, at 1000 kPa, the pressure raising valve opens allowing liquid oxygen to shunt through a pressure-raising vaporiser and allow environmental heat to enter LOW USAGE (hot weather): temperature of liquid oxygen increases and pressure increases, blow off valve opens to allow vapour into the environment

Answer 103

* Bicarbonate * Base Excess

Answer 104

* Common Dead Space: an alteration in the administration rate of one drug will affect the others * Reflux: obstruction can cause drugs to go up gravity-fed lines (they need anti-reflux valves) * Siphoning: if a syringe driver is placed above the patient and the syringe plunger is not held firmly in place, the difference in hydrostatic pressure can make the drug flow freely. They have anti-siphon valves.

Answer 105

A capacitor with capacitance of 1 Farad will store 1 Coulomb of charge when 1 Volt (not Amp) is applied across it.

Answer 106

* A **pencil-point needle** (e.g. Whitacre or Sprotte) has a rounded, non-cutting tip with a side hole for drug delivery. It spreads dural fibers rather than cutting them, reducing the risk of post-dural puncture headache (PDPH). * A **cutting needle** (e.g. Quincke) has a sharp, beveled tip that slices through tissues, making dural puncture easier but increasing the risk of PDPH due to greater dural trauma.

Answer 107

1. Earthed 2. Double Insulated 3. Safe extra low voltage (24-50 V)

Answer 108

* Suction * Reservoir * Centrifuge * Washing * Filtration * Reinfusion Bag ## Footnote **SUCTION**: collects blood using heparin or citrate to prevent clotting **RESERVOIR**: stores and roughly filters blood, removing large clots **CENTRIFUGE**: separates red cell from plasma and contaminants **WASHING**: isotonic saline removes free haemoglobin, activated clotting factors and anticoagulants **FILTRATION**: leukocyte depletion filter to remove white cells and microaggregates **REINFUSION BAG**: stores concentrated clean red cells for transfusion

Answer 109

* Both are co-axial * Lack behaves like a Mapleson A (FGF on outside) * Bain behaves like Mapleson D (FGF on inside). Can theoretically be infinitely long as the FGF is delivered at the patient end.

Answer 110

* Flat for 24 hours before use. * Invert at least 3 times before use. ## Footnote This is because oxygen is less dense than N2O so would be delivered first, leaving an increasing concentration of N2O and, eventually, a hypoxic mixture as the canister is used up.

Answer 111

* Schrader Sockets: unique diameter index collar matches the relevant socket * Flexible, kink-proof colour-coded pipe (blue for nitrous, white for oxygen, black for air) * Non-Interchangeable Screw Thread: nut and probe with unique profile for each gas, unidirectional valve

Answer 112

Dumbbell of nitrogen is aligned perpendicular to a magnetic field and balanced on a suspending filament Oxygen will be attracted to the magnetic field causing a deflection in the dumbbell Photocells are used to control a variable current that induces a magnetic field that exactly offsets movement due to oxygen - the current is used to calculate oxygen concentration

Answer 113

Steel alloy ## Footnote e.g., manganese molybdenum steel, chromium molybdenum steel, or nickel chromium steel

Answer 114

SLUDGE syndrome | (salivation, lacrimation, urination, defecation and emesis) ## Footnote E.g. organophosphate poisoning Treated with atropine or pralidoxime

Answer 115

Radiation energy per unit time from a black body is proportional to the fourth power of the absolute temperature.

Answer 116

Is a dimensionless quantity which quantifies the ability of a body to radiate heat. This is expressed as a comparison to a perfect black body surface at the same temperature (a black body has a value of 1).

Answer 117

Thermodynamic process in which a gas expands without exchanging heat with its surroundings. ## Footnote Any change in internal energy comes solely from work done by the gas. It leads to a drop in temperature, since the gas does work but receives no heat to compensate.

Answer 118

When the system oscillates with maximum amplitude. ## Footnote This occurs when the external driving frequency equals the natural frequency of the material.

Answer 119

Frequency at which a system oscillates when displaced from its equilibrium position and allowed to vibrate freely without any external forces acting on it.

Answer 120

The Doppler shift equation describes the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. ## Footnote It is commonly used in physics to explain phenomena such as the change in pitch of a passing siren.

Answer 121

Consists of a C-shaped hollow spring-like tube that extends outwards at the sealed end when pressure rises in the tube. ## Footnote The expansion and contraction is relayed to a pointer that indicates the pressure on a calibrated dial

Answer 122

Turning a screw adjusts the spring and diaphragm. When lowered, more pressure is needed to lift the diaphragm for gas to escape. The valve allows adjustment of blow-off pressure by changing the spring's position.

Answer 123

Supplies gas flow to an outlet (e.g., facemask) at lower pressure than the supply (e.g., cylinder). Gas enters a chamber through an aperture around a piston. If chamber pressure is too high, the diaphragm and piston rise to narrow the aperture, restricting gas flow and reducing outflow pressure.

Answer 124

Uses two thermometers: a dry bulb for ambient temperature and a wet bulb with a water-saturated wick. Evaporation from the wick cools the wet bulb, and the temperature difference indicates relative humidity.

Answer 125

Hair contains cytokeratin molecules linked by disulphide bridges and hydrogen bonds. Moisture absorption causes hair to lengthen, with the degree of lengthening indicating relative humidity, which can be calibrated for readings.

Answer 126

Exhaled warm, moist air condenses on the material, releasing latent heat. On the next inhalation, dry gas passes over the warm, moist material, becoming warmed and humidified. Approx. 80% efficient in conserving heat and moisture. A 0.2 µm filter can block bacteria/viruses, preventing circuit contamination. ## Footnote Made of calcium chloride or silica.

Answer 127

100 mL in adults Up to 2 cm H2O resistance

Answer 128

A fluid or gas stream will hug a convex contour when directed at a tangent to that surface.

Answer 129

Measures airflow by detecting pressure differences across a fine mesh in a tube (fixed resistance). This pressure difference, sensed by sensors, is proportional to flow rate under laminar conditions. A widened tube ensures laminar flow by reducing velocity and the Reynolds number.

Answer 130

8.31 J/K/mol

Answer 131

Generates infrared radiation from a heated wire, filtered to a specific wavelength absorbed by the target gas. Gas passes through a chamber with infrared-permeable windows (e.g., sapphire), and a photodetector measures the radiation that passes through. The absorbed radiation indicates gas concentration (Beer's law).

Answer 132

Fresh gas flow splits: some enters a vaporising chamber, while the rest bypasses it. Positive pressure pushes carrier gas through the chamber, picking up vapour from the volatile agent. Gases rejoin before reaching the patient. The splitting ratio controls anaesthetic concentration and can be adjusted. Vaporiser must maintain the agent's **SVP** for accurate delivery.

Answer 133

The pressure will just show SVP until all the liquid has evaporated When empty, it will contain 1 atmosphere (hence, there is no gradient drawing more gas out).

Answer 134

Oxygen is stored as a liquid at high pressure (7-10 bar) and low temperature (-150 to -180°C). The VIE is a thermally insulated vessel with an inner stainless steel shell and an outer carbon steel shell. 1 L of liquid oxygen produces 860 L of gaseous oxygen at STP. An electrical warmer brings the oxygen to room temperature.

Answer 135

How close a measured or estimated value is to the true (or actual) value.

Answer 136

A material that allows the flow of charge through it because of loose outer electrons.

Answer 137

A material that resists the flow of electric current because it has very few free charge carriers (electrons or ions).

Answer 138

The absolute pressure minus the reference pressure (usually atmospheric pressure).

Answer 139

A component which opposes the flow of current by creating an electromotive force.

Answer 140

The ability of a measuring device to reproduce a value when given the same input

Answer 141

* Thermistor (temperature probe) * Transistor (control switches) * Diode (defibrillator)

Answer 142

Glucose in blood is oxidized by glucose oxidase, releasing electrons. These electrons are transferred to the electrode, completing the circuit. The measured current is proportional to glucose concentration.

Answer 143

* Galvanic fuel cell * Clark electrode * Paramagnetic oxygen analyser

Answer 144

0.2-0.5 msec ## Footnote NOTE: This is a square wave pulse.

Answer 145

* Ulnar nerve * Facial nerve Posterior tibial nerve

Answer 146

-0.5 kPa 10 kPa

Answer 147

-39 to 250 degrees centigrade

Answer 148

Light Amplification by Stimulated Emission of Radiation

Answer 149

**Device for Indirect Non-invasive Automated MAP** measurement. Measures SBP and MAP (derives DBP).

Answer 150

The process of comparing the output or measurement of an instrument to a known reference or standard, and adjusting it if necessary to ensure accuracy.

Answer 151

Gradual deviation of a measuring instrument’s output from the true value over time, without any change in the measured variable.

Answer 152

* Sensor contamination (moisture, secretions) * Sampling line defect (obstruction, leak) * Low tidal volumes * Collision broadening (nitrous oxide) * Temperature (higher temperature means lower gas density, fewer CO2 molecules to absorb IR --> under-read)

Answer 153

* Narrow band IR filter * Water trap * Calibrate with gas mixture containing background gas

Answer 154

**Wavelength**: 700-1000 nm **Frequency**: 0.3-400 THz

Answer 155

* Regional anaesthesia * Insertion of intravascular devices (e.g. CVC, cannulas) * Oesophageal doppler * Focused lung and heart ultrasound

Answer 156

* Gas analysis (CO2, N2O, anaesthetic gases) * Pulse oximetry * Infrared temperature probe

Answer 157

* Single limb vs. circle system * Pneumatically driven vs. bellows * Smaller and more compact * Cylinder gas supply instead of wall * No scavenging * No rebreathing * Battery powered

Answer 158

There is an exhalation valve that can be adjusted to control PEEP.

Answer 159

* 30 mm diameter (wide-bore) * Withstands negative pressure * High flow (80 L/min) ## Footnote NOTE: the float is a visual indicator of adequate flows

Answer 160

It is a pneumatically driven ventilator that displaces fresh gas flow within a Bain (co-axial Mapleson D) into the patient. The compressible tube must exceed the patient's tidal volume to prevent the driving gas from being inhaled.

Answer 161

Describes how a light ray changes direction when it passes from one medium to another with a different refractive index. ## Footnote NOTE: Bends towards normal when entering a denser medium, and away in a less dense medium.

Answer 162

A measure of how much a medium slows down light.

Answer 163

Complete reflection of light back into its original medium when it strikes the boundary of another medium at an angle greater than the critical angle.

Answer 164

Minimum angle of incidence at which light traveling from a denser medium to a less dense medium is completely reflected back into the denser medium, instead of refracting into the less dense medium.

Answer 165

* **ONE-POINT**: linear, narrow-range devices (e.g. arterial line) * **TWO-POINT**: moderately non-linear or moderate-range devices * **MULTI-POINT**: highly non-linear, wide-range, or critical devices (e.g. blood gas monitor)

Answer 166

Condition where more atoms are in an excited state than in the ground state, allowing stimulated emission to amplify light.

Answer 167

Thermopile - converts infrared into a small electrical voltage.

Answer 168

Narrow tubing means shorter transit time and less gas mixing. Connection should be on machine side - this means the HMEF protects the sampling line from moisture and secretions.

Answer 169

* Absorbs 100% of all electromagnetic radiation that falls on it (no reflection, no transmission). * Emits electromagnetic radiation with a spectrum that depends only on its temperature (called black-body radiation).

Answer 170

Force per unit area that acts parallel to a surface. ## Footnote E.g. Tangential forces experienced by alveolar walls when layers of lung tissue slide unevenly relative to each other.

Answer 171

* Laser-resistant outer layer (steel or aluminium wrap) * Non-PVC material * Double cuff (saline or methylene blue filled)

Answer 172

The temperature at which the vapour pressure of a liquid equals the surrounding ambient pressure and the liquid changes into a vapour.

Answer 173

The temperature at which the liquid and solid phases of a substance of specified composition are in equilibrium at a given pressure. ## Footnote A liquid turns into a solid when its temperature is lowered below its freezing point.

Answer 174

* **ANALOGUE** – output signal is continuous, e.g. the waveform display of an arterial pressure trace. * **DIGITAL** – output signal is discontinuous, e.g. the numerical display of BP next to the arterial waveform.

Answer 175

* **RESPONSE TIME**: time for output to reach 90% of final reading * **RISE TIME**: time for output to rise from 10 to 90% of final reading

Answer 176

* Pneumotacograph * Wright respirometer * Rotameter

Answer 177

* **CAPACITIVE** reactance decreases with increasing frequency. * **INDUCTIVE** reactance increases with increasing frequency. ## Footnote NOTE: The variation in reactance with frequency makes capacitors useful filters.

Answer 178

Increasing pressure raises boiling and melting points.

Answer 179

* Freezing point * Boiling point * SVP * Osmotic pressure

Answer 180

A spring-loaded bobbin valve alternates between opening and closing the inspiratory and expiratory ports. Squeezing the bag closes the expiratory port to deliver gas, while during expiration, it closes the inspiratory port. It can jam.

Answer 181

* **Class 1**: Eye exposure always below safe limits. * **Class 2**: Visible lasers ≤ 1 mW; normally safe due to blink reflex. * **Class 3A**: Visible lasers ≤ 5 mW with beam expansion to limit irradiance; blink reflex still protective. * **Class 3B**: Up to 0.5 W at any wavelength; direct viewing is dangerous—eye protection required. * **Class 4**: > 0.5 W at any wavelength; severe eye/skin hazard and fire risk—strict protection essential.

Answer 182

It does NOT lose power with distance. ## Footnote This is because it forms a collimated (non-divergent) beam.

Answer 183

The MRI room is lined with copper or aluminium to act as a Faraday cage, preventing external radio-frequency interference from entering and degrading the MRI signal.

Answer 184

* **HIGH LEVEL** (e.g. glutaraldehyde): almost sterilisation, used for semi-critical items that touch mucous membranes (e.g. laryngoscope) * **LOW-LEVEL** (e.g. 70% alcohol): routine surface cleaning for non-critical items that touch intact skin only (e.g. BP cuff)

Answer 185

* **CRITICAL** (e.g. needles): Enters sterile body tissues or bloodstream, needs sterilisation * **SEMI-CRITICAL** (e.g. laryngoscope): contacts mucous membranes but does NOT penetrate tissue, needs high-level disinfection * **NON-CRITICAL** (e.g. BP cuff): contacts intact skin only, needs low-level disinfection

Answer 186

Rate of change of a quantity is proportional to its current value.

Part 4: Physics & Equipment Flashcards

Apply principles of physics and measurement to anaesthesia, including pressure, flow, gas laws, vaporizers, electrical safety, and monitoring. (217 cards)