Equipment - OSCE Station Info

Question 1

Pseudocritical temperature of entonox

Answer 1

• 5.5 degrees at 117 bar

- 30 degrees at 4.1 bar

Question 2

What is the Poynting effect?

Answer 2

The gaseous mixture of nitrous oxide forms when oxygen is bubbled through liquid nitrogen causing vapourisation of the liquid.

Question 3

OXYGEN:

cylinder color and pin index

Answer 3

black body, white shoulders

2 + 5

Question 4

AIR:

Cylinder color and pin index

Answer 4

Black body, black and white checkered shoulders

1 + 5

Question 5

NITROUS OXIDE

Cylinder colour and pin index

Answer 5

French blue body

3 + 5

Question 6

4 pieces of information engraved on a cylinder

Answer 6

1. Serial number
2. Tare weight
3. Tare pressure
4. Date of testing

Question 7

3 methods of testing a cylinder

Answer 7

1. Endoscopic examination
2. Tensile testing
3. Pressure testing up to 22000 kPa

Question 8

What type of flowmeter is a rotameter?

Answer 8

Constant pressure, variable flow orifice device

Question 9

Components of a rotameter?

Answer 9

1. Vertical tapered tube
2. Floating bobbin
3. Valve at the bottom which controls flow into the tube
4. scale representing the flow

Question 10

What is the theory behind the rotameter flow measurement?

Answer 10

There is a constant flow across the rotameter but a variable resistance due to the change in diameter of the tube.

Question 11

How does the rotameter overcome friction?

Answer 11

1. The bobbin is skirted so that it spins when gas flows past preventing it from sticking.
2. The tubes coated with tin oxide to allow electrostatic forces to be earthed.

Question 12

How would a change in temperature affect measurement of the flow at low flow rates in a rota meter?

Answer 12

Temperature increases the viscosity and lowers the density of a gas, therefore at lower flow rates there would be an over reading.

Question 13

How would you examine a Bains circuit to ensure it was safe to use? (8 marks)

Answer 13

1. VISUAL INSPECTION - correct assembly, no cracks, tears in reservoir bag
2. INNER TUBING - turn up O2 flow, occlude inner tube with plunger. Integrity confirmed if bobbin drops due to back pressure.
3. OUTER TUBING - occlude outer tube with thumb, fill reservoir bag, and increase pressure or turn gas flow down, ensure bag does not collapse.
4. PETHICKS TEST - close APL valve, fill bag and breathing system using O2 flush while occluding outer tube with thumb. Release occlusion whilst still pressing the oxygen flush and venturi effect will cause bag to collapse.

Question 14

What is the effect of increasing the length of tubing in Bains circuit?

Answer 14

Can increase resistance to expiration in spontaneous breathing.

Question 15

How can a Bains circuit be attached to the ventilator?

Answer 15

Remove reservoir bag,
close APL valve
and attach 1 meter of corrugated tube to tubing
(tube volume > 500 ml to prevent driving pressure from ventilator being applied to patient)

Question 16

What is the difference in laryngoscopy between using a curved or a straight blade?

Answer 16

Curved blade - the tip is placed in the vallecula behind the epiglottis, used to lift larynx

Straight blade - the tip is used to lift the epiglottis directly to reveal the cords (useful in paediatrics as small children have long floppy epiglottis)

Question 17

What types of blades are available for laryngoscopy?

Answer 17

— Macintosh (commonest; blade attaches to handle at 90 degrees)

— McCoy (Macintosh like blade with a moveable distal tip segment, flexed by a lever controlled by the thumb of the hand holding the handle to displace the larynx forwards)

— Magill (straight blade with U-shaped cross section)

— Miller and Wisconsin blades (straight blades with curved tips)

Question 18

What are the two difference between fibre optic laryngoscopes and conventional laryngoscopes with bulbs?

Answer 18

1. Conventional have light bulb at tip of laryngoscope so that is the source, whereas fibreoptic the source of light is at the handle.
2. In conventional laryngoscopes the light comes on when an electrical connection is made between the handle and base of the blade - therefore could flicker.
   With fibreoptic there is a light conducting glass/ plastic, which converges light from the top of the handle to the distal portion of the blade.