8: anaesthesia and ventilators

Question 1

Overview of anaesthesia machine

Answer 1

• Gas supply- mains pipelines or cylinders
• Gas flow measurement and control (flow meters)
• Vaporisers
• Gas delivery
• Scavenging system
• Monitoring
• SPDD model- supply&raquo_space; processing&raquo_space; delivery&raquo_space; disposal

Question 2

Gas lines

Answer 2

• Oxygen
• CO2
• Nitrous Oxide
• Scavenging line

Question 3

Flowmeters

Answer 3

• Low flows- orifice around float is tubular = flow determined by viscosity
• High flows- orifice more open = density determines flow
• Rotameter either conical or ball shaped
• Tapered tube used

Question 4

Medical gases

Answer 4

• Sevoflurane- easy to inhale but short acting
• Desflurane- very short acting, less easy to breathe,&raquo_space; HR and BP
• Isoflurane- ICU purposes

Question 5

Semi-closed system

Answer 5

• Requires a CO2 absorber to collect expired CO2
o Soda lime used
• Humidification also required

Question 6

Components of ventilator

Answer 6

• Primary and secondary sources of gas (O2 and air)
• Gas blending system
• Breathing circuit
• Humidifier
• Nebuliser