Anaesthetic equipment Flashcards

1
Q

Sources of anaesthetic gases in an anaesthetic machine?

A

They can be obtained from cylinders or pipelines

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2
Q

Types of pressure systems & their component?

A
  1. Cylinders - high pressure system
  2. Hospital pipeline - Intermediate pressure system
  3. Anaesthesia machine - Low pressure system
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3
Q

Components of the high pressure system?

A
  1. Oxygen & nitrous cylinders
  2. Non-return valves
  3. Pressure guages
  4. Primary pressure regulator
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4
Q

Pressure regulators?

A

The transform high pressure systems to intermediate pressure systems.

There are two stages of oxygen pressure regulation

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5
Q

Components of the low pressure system?

A
  1. Flow meters
  2. Vaporizer
  3. Common gas outlet
  4. APL valve at 35 kPa
  5. Breathing system (Newer machines)
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6
Q

Components of the intermediate pressure system?

A
  1. Nitrous & Oxygen pipeline supply
  2. Pipeline pressure guage (300 - 400 kPa)
  3. Fail safe valve
  4. Oxygen supply failure alarm
  5. Second stage oxygen pressure regulator
  6. Oxygen flush valve
  7. Flow control valves
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7
Q

Cylinder pressures and reduced pressures?

A

The pressure is reduced by the presssure regulator from 1,444 - 4000 kPa to 310 - 420 kPa ( To protect patient, apparatus and maintain constant pressure.

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8
Q

Cylinders - This is a safety feature in the anaesthetic machine?

A

Colour coded and specific pin index system

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9
Q

ISO system ?

A

Shoulder-body

  1. Carbondioxide - Grey
  2. Heliox - White/Brown
  3. Air - White/Black
  4. Nitrogen - Black
  5. Nitrous Oxide - French Blue
  6. Oxygen - White / Black
  7. Entonox - white/Blue
  8. Helium - Brown/Brown
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10
Q

Cylinders?

A
  1. Made of chrome-molybdenum steel or carbon steel
  2. Size is determined by water capacity in litres
  3. N2O & CO2 are liquified gases under pressure. Pressure is constant until cylinder is empty
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11
Q

Calculation of cylinder gas content?

A

Gas content = Water capacity (L) x Pressure (bar)

The pressure must be in bar - Learn conversion of pressures

bar psi kPa MPa
0.1 1.5 10 0.01

The cylinder for N2O and CO2 must be weighed to get the gas content

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12
Q

Safety devices to secure oxygen delivery?

A
  1. Fail-safe valve

Limit is 21% oxygen delivery

Detect pressure based on pressure and not flow - Doesn’t protect against hypoxic gas delivery.

  1. Anti-hypoxia devices (Flow regulator)- This reduces oxygen pressure to 14 psig and 26 psig for N2O
  2. Oxygen flush - @ 35 L/min from pipeline or cylinder. May cause dilution & barotrauma
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13
Q

Ritchie whistle?

A
  1. This makes a whistling sound.
  2. Its at 60 db
  3. At 1 meter form the anaesthetic machine
  4. Lasts for 7 secs
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14
Q

Properties of mechanical (Rotameter)?

A
  • Constant pressure & variable orifice
  • Caliberated for a particular gas
  • The flow are within 10% of the indicated flow
  • Reading taken from the top of bobbin (triangle shape) or in the middle in the round ones
  • Oxygen must be the last rotameter before the gas outlet
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15
Q

Hybrid flowmeters?

A
  • Works with needle valve
  • Flow generated without electric power
  • Measurment and display are electronic.
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16
Q

Electronic flow meters?

A
  1. Fully electronic
  2. No manual valve
  3. Backed up by basic O2 delivery system in case power or machine failure.
17
Q

Where is the location of the vaporizer in the breathing system?

A
  1. Located between the flowmeter and common gas outlet
18
Q

Boiling point and altitude?

A
  • The temperature at which vapor pressure is equal to atmospheric pressure
  • Boiling point decreases with increase in altitude.
19
Q

Mechanics of the Variable bypass vaporizers?

A
  1. Split into two by the spliting valve

2. On part free from volatile and the other is saturated with volatile

20
Q

Types of variable bypass vaporizers?

A
  1. Draw over

2. Plenum

21
Q

Properties of the draw over vaporizer?

A
  1. Gases are at atmospheric pressure
  2. Drawn through the vaporizer by the inspiratory efforts of the patient
  3. Low resistance vaporizer
  4. Poor accuracy - Dependent on patient’s effort
22
Q

Plenum vaporizers?

A
  1. Inspired gases are at higher than atm pressure
  2. High resistance vaporizer
  3. It is accurate is wide rage of flows and temperatures
  4. It has a temperature compensator in the bypass circuit
  5. It can be used at altitude due to partial pressure remaining constant
23
Q

Patial pressure of Volatile agents at altitude?

A
  1. Partial pressure of volatile agent remains constant at altitute
24
Q

TEC 6 vaporizer for desflurane?

A
  1. It has a boiling point of 23.5
  2. Desflurane heated to 39 degrees under a pressure of 194 kPa or 1500mmHg
  3. Continuous flow of desflurane is added to the FGF
  4. Shut off valve is activated by tilting the vaporizer
25
Q

Sevoflurane vaporizer?

A
  1. No shut off valve
  2. It has a transport setting
  3. There is a pin safety system for all volatiles
26
Q

Breathing systems?

A

See mapleson system in pictures

27
Q

Where is the APL valve located in Circle system?

A
  1. APL valve is located in the expiratory limb
28
Q

Soda lime ?

A
  1. Absorbs 23L of co2 per 100 g.
  2. Its main component is calcium hydroxide
  3. End product : Heat, water and calcium carbonate
  4. Barium hydroxide not used as it easily catches fire
29
Q

Anaesthetic gas analysis?

A
  1. Mass spectrometry and Raman spectroscopy are not used anymore
  2. Most gases measured by infrared analysis
  3. O2 and N2 do not absorb infrared light (Only one atom)
30
Q

CO2 analysis?

A
  1. Infrared analysis

2. Principle Beer-lambert law

31
Q

Beer-lambert law?

A

The absorption of infrared light passing through a solvent (gas) is proportional to the amount of the unknown gas

32
Q

Oxygen analysis ?

A
  1. Galvanic cell (Fuel cell) : Lead anode and gold cathode in potassium chloride. At gold terminal hydroxyl ions are formed that react with lead. Used on anaesthetic machines in the inspiratory limb.
  2. Paramagmetic analyser: Expands in magnetic field and contracts when magnetic field turned off, its paramagnetic. It requires a water trap.
  3. Polarographic electrode: Gold or platinum cathode and silver anode. Separated by semipermeable membrane . Works with small voltage applied to the electrodes. Amount of current flowing through the anode and cathode is proportional to the amount of O2 present
33
Q

Invasive arterial monitoring?

A
  1. It has electromanometer diaphragm with built-in strain guage (Wheatstone bridge principle)
  2. Wave form built up by fourier analysis
  3. Doesn’t matter where the transducer is zero’ed
34
Q

Damping ?

A
  1. Over-damping - Flat arterial curve
  2. Under-damping - High peaks
  3. Blood clot will cause overdamping
  4. Air bubbles will cause under-damping
35
Q

Electrical safety?

A
  1. If the body is in contact with two conductive surfaces at different potential, it may complete a circuit and result in electrical shock
  2. Defibrillation threshold is 100microA (fatal to heart)
  3. Maximum leakage allowed 10 microAmpre in OR
36
Q

Surgical diathermy ?

A
  1. Uses ultrahigh frequencies - 0.1-3MHz compared with line power 50-60Hz
37
Q

Incidence of Fires and thermal injuries?

A
  1. Incidence of surgical fires 1 in 87,000 cases

2. ETT to be used if >30% FiO2 and surgical site above the xiphoid