Anaesthesia Equipment

Question 1

What is Anaesthesia and what are the 2 types ?

Answer 1

Anaesthesia is the loss of sensation.
Local (numbs certain areas of your body) and general (controlled unconsciousness)

Question 2

What are the key functions of an aesthesia machine ?

Answer 2

Provide Oxygen and stable ventilation (if needed) to a patient.
Mix gases with anaesthetic gases.
Minimise anaesthesia related risk.

Question 3

What subsystems are found in modern anaesthetic machines ?

Answer 3

High Pressure System (from cylinders to pressure reducing valves )
Intermediate Pressure System. (from pressure reducing valves to the flowmeters )
Low Pressure System (from flowmeters to common gas outlet )

Question 4

What features may be present in a block diagram for an anaesthesia machine ?

Answer 4

Gas pipelines
Flowmeters for each gas
Hypoxia guards
A vaporiser to mix gases
A common manifold (plumbing)
Common Gas Outlet (CGO)
Scavenging Circuit (to reduce gas waste )
Breathing Circuit
Disposal Tubing

Question 5

What gases may be used as the anaesthetic gas?

Answer 5

Nitrous Oxide
Halothane
isoflurane
desflurane

Question 6

What is hypoxia and how is it prevented in some anaesthetic machines ?

Answer 6

Hypoxia is a condition where part of the body is deprived of adequate oxygen supply. Hypoxia guards are used to prevent this.

Question 7

How do hypoxia guards function ?

Answer 7

Found in low pressure part of machine . Works by moving oxygen levels up proportionally when increasing anaesthetic and reducing anaesthetic levels proportionally when oxygen levels are reduced. This is usually done by a gear system which involves keeping a specific ratio (around 1:3 O2 : N20 )

Question 8

What are the main gases used in an anaesthetic machine and what colour are the pipelines which carry them ?

Answer 8

Nitrous Oxide (or another anaesthetic ) –> BLUE
Oxygen – > WHITE
Air –> BLACK

Question 9

What electrical components are used in an anaesthesia machine ?

Answer 9

Master Switch –> to turn on and off the electrical and pneumatic functions.
Power Failure Indicator (ALARM)
Reserve Power
Automated machine checks
Data communication
Electrical Outlets (for the monitors) + Circuit Breakers.

Question 10

What safety features are present before the high pressure system ?

Answer 10

Gas cylinders as back ups to the pipeline gas.
Colour coding on the gas tubing.
Tubing contains Shrader probes and sockets which only fit the correct tubing. Means N2O cant connect to O2 port.
One way valves to ensure unidirectional flow.

Question 11

What features are present in the high pressure system ?

Answer 11

Gas cylinders -> contain gas at high pressures and have thin steel walls to withstand this.
Yoke and bodok seals
Check valves (one way flow valves ) -> prevent leakage when changing cylinders and filling of empty cylinders.
Pressure regulator valves

Question 12

What does a yoke and bodok seal do ?

Answer 12

The yoke supports the cylinder and provides an airtight seal. Contains a pin index to prevent the cylinder form being attached to the wrong inlet.
A bodok seal is a bonded disk seal which provide gas tight seals in place of grease.

Question 13

What pressures do the regulator valves operate at ?

Answer 13

Entry pressure is around 4 bar( 400kPa) and exit pressure is around 1 bar. Greater than 525kPa sets of the safety valve on the regulator. The regulator functions using the F = P x A equation and balances force. Pressure is reduced by applying the large pressure to a small area which is equivalent to a large area with a smaller pressure.

Question 14

What features are found in the intermediate system ?

Answer 14

Pipe inlet connections
Oxygen supply failure alarm
Oxygen flush valve
Oxygen failure safety device.

Question 15

What features are found in the low pressure system ?

Answer 15

Flowmeters (for each gas )
Hypoxic guards
Vaporizers
Common gas outlets

Question 16

What are the requirements of a breathing circuit ?

Answer 16

transportation of gases from the common gas outlet
predictable inspired CO2 concentrations.
allow adequate CO2 elimination.
Predictable anaesthetic concentrations.

Question 17

What are the types of breathing circuits ?

Answer 17

Non rebreathing –> High flow of gas to flush CO2 contains APL valve and reservoir bag. (IN ANAESTHESIA MACHINE AND PATIENT TRANSFERS)
Rebreathing –> functions using a circle system. Contains soda lime to remove CO2 and oxygen and anaesthetic is recycled. (with sufficient 02 added). Flows at 1L/ min. (COMMON IN OPERATING ROOMS)

Question 18

What features may be included in the breathing circuit ?

Answer 18

One way valves for the expiratory and inspiratory sides of the circuit. –> prevent backflow into patient.
Adjustable Pressure limiting valves –> doesn’t allow low pressure through and allows high pressure. (spring based )
Y type tubing – > specifically in circular system.
possibly fresh gas inlet from anaesthetic machine.

Question 19

What are the 3 types of ventilators and what factors can be set on a ventilator ?

Answer 19

Mechanical, pneumatic or electronically controlled.
Factors include
volume - can set volume by tidal volume and frequency.
pressure - avoid lung damages by setting higher than airway pressures.
modern machines can control specific inspiration and expiration times.

Question 20

What features are present in a ventilator circuit ?

Answer 20

Control valves and controllers for oxygen and air.
Microprocessor controlling airway pressure and sending information to controller.
Other microprocessor controlling monitoring.
Airway pressure sensors on a pressure sensing tube connected to the patient.
O2 and air sensors.

Question 21

What is scavenging and how does it work ?

Answer 21

Passing of waste anaesthetic gas through a charcoal which absorbs halogenic anaesthetics. Removes anaesthetic gas from the room environment.
Ensures pressure on exhaust valves doesn’t become too high or too low.

Question 22

What things are monitored on an anaesthetic monitor ?

Answer 22

Pulse Oximetry
Electrocardiography
Non invasive blood pressure
Anaesthetic agent monitoring
Airway Pressure
End tidal capnography.