General Anesthesia Machine Pneumatic Systems

Question 0

What are the components of the High-Pressure system?

Answer 0

1. Hanger Yoke
2. Gas Cylinders
3. Cylinder Pressure Gauge
4. Cylinder Pressure Regulators
5. Check Valve

Question 1

What are the 3 pressure systems and their corresponding pressure range?

Answer 1

1. High-Pressure (1900-2200 psi)
2. Intermediate-Pressure (37-55 psi)
3. Low-Pressure (variable <37 psi)

Question 2

What is the component of the Hanger Yoke?

Answer 2

• PISS

Question 3

What are the Gas Cylinders?

Answer 3

1. Oxygen (1900-2200 psi, 660L)
2. Nitrous Oxide (745 psi, 1600 L)
3. Air (1800-1900 psi, 600 L)

Question 4

What are the components of the Cylinder Pressure Gauge?

Answer 4

• Electronic or Bourdin type

Question 5

What is the function of the Cylinder Pressure Regulators?

Answer 5

• Decreases gas pressure and maintains constant pressure supply to the intermediate pressure system
• Outlet pressure is lower than wall pressure to maintain preferential wall pressure supply if tank is left open (NOT fool proof, important to keep cylinders closed)

Question 6

What is the function of the Check Valve?

Answer 6

• Prevent exit of gas from the machine when no cylinder is present
• Prevents transfilling of gas from one cylinder to another

Question 7

What are the components of the Intermediate-Pressure system?

Answer 7

1. Master Switch
2. Pipeline Inlet Connections
3. Pipeline Pressure Gauges
4. Oxygen Pressure Failure Device (Fail Safe)
5. Oxygen Supply Failure Alarm
6. Gas Selector Switch
7. Second Stage Pressure Regulator
8. Oxygen Flush
9. Flow Adjustment Controls
10. Alternate Oxygen Control

Question 8

What is the Master Switch?

Answer 8

• When off, pressure in the intermediate system falls to zero

Question 9

What are the Pipeline Inlet Connections?

Answer 9

• DISS

- Check valve at inlet prevents reverse gas flow from machine to pipeline

Question 10

What should the Pipeline Pressure Gauges read?

Answer 10

• They should read 50-55 psi

Question 11

What is the Oxygen Pressure Failure Device (Fail Safe)?

Answer 11

• Loss of Oxygen pressure results in cessation of Nitrous gas flow
• Only senses pressure, not what type of gas is present so it does not prevent potential hypoxic mixture in the case of a pipeline crossover or a cylinder with the wrong gas

Question 12

What is the Second Stage Pressure Regulator?

Answer 12

• Reduces pressure from pipeline to flowmeters (not present on all machines)

Question 13

What is the Oxygen Flush?

Answer 13

35-37 L/min to common gas outlet

Question 14

What is the Alternate Oxygen Control?

Answer 14

• Electronic Flowmeter backup (Aysis) in case of electrical failure.

Question 15

What are the components of the Low-Pressure system?

Answer 15

1. Flowmeters
2. Hypoxia prevention safety devices
3. Unidirectional Check Valve (Aespire)
4. Pressure Relief Device
5. Common (Fresh) Gas Outlet
6. Auxiliary Oxygen Flowmeter

Question 16

Describe Flowmeters?

Answer 16

• Electronic or Variable Orifice (Thrope)
• Variable Orifice (Thorpe)
• Low flows = laminar; viscosity, Hagen-Poiseuille law
• High flows = turbulent; density, Graham’s law

Question 17

Describe the Hypoxia Prevention Safety Devices?

Answer 17

• O2 - N2O Link System

Question 18

Describe Unidirectional Check Valve (Aespire)?

Answer 18

• Located between the vaporizers and the common gas outlet upstream of where the oxygen flush flow joins the fresh gas flow
• Prevents back pressure to the vaporizers and flowmeters from positive pressure in the breathing circuit
• Negative pressure leak test checks function of the valve

Question 19

Describe the Pressure Relief Device?

Answer 19

• Near common gas outlet to prevent and protect machine from high pressure

Question 20

Describe Common (Fresh) Gas Outlet?

Answer 20

• May be internal on newer machines

Question 21

What are the components of the Breathing Circuit?

Answer 21

• Y port
• CO2 Absorber
• Inspiratory and Expiratory Valves
• APL
• Reservoir Bag