1. The Anesthesia Gas Machine
Karen Garcia
N747 Evidence Based Practice for Nurse Anesthesia

2. Components of the Gas Machine
Valves
High Pressure System
Immediate Pressure System
Low Pressure System
Circle System/Breathing Systems
Will only touch on cylinders to prevent a long lecture! Will go over review questions for us to discuss.

3. Valves Free Floating/Check Valves Ball and Spring Diaphragm Valves
Picture is of a check valve. Note how it is unidirectional.

4. Free Floating/Check Valves
Unidirectional
Located in various parts of the machine
Diameter Index Safety System
Prevents oxygen cylinder gas from escaping the anesthesia machine and going out hospital wall
Check Valve between Vaporizer Outlet and Common Gas Outlet
Prevents reversal of flow to vaporizer
Not Present on all machines (Ohmeda only)

5. “Ball and Spring” Type Valve
You supply the energy for this valve!
Oxygen Flush Valve
Pressurized at psi from wall or cylinder
Oxygen delivered to patient at L/minute
May cause barotrauma
Is this considered high, intermediate, or low pressure?
Intermediate

6. Diaphragm Valves Regulate and Reduce Pressure First Stage Regulator
Cylinder pressure decreased to 45 psi
Why is cylinder pressure slightly less than pipeline pressure?
Second Stage Regulator
Receives wall pressure oxygen or from first stage regulator
Only Ohmeda machines
Slightly less than pipeline pressure to prevent depletion of cylinder contents when attached to pipeline

7. Quick Review Questions: Cylinders
What is the cylinder pressure and capacity for oxygen?
Cylinder pressure and capacity for nitrous oxide?
Who regulates marking, labeling, filling, handling, and transportation of compressed gas cylinders?
psi; 660L
psi; 1590L
Dept of Transportation

8. Cylinders (continued)
Each valve stem on the cylinder has a safety device under which hazardous conditions of excessive heat or fire will cause the cylinder to become exhausted. What is this safety device called?
What is this safety device composed of? At what temperature will it melt?
Wood’s Metal
Composed of bismuth, lead, tin, and cadmium (BLT with Cheese)
Melts at 200 deg F

9. High Pressure System Think Cylinder Pressure! Components
Cylinder Pressure Regulator (aka First Stage Regulator)
Cylinder Pressure Gauge
Hanger Yoke, Yoke Block, and Yoke Plug
Yoke Block with Check Valves (Free Floating)
Pin Index Safety System
Pretty much what is exposed to cylinder pressure

10. Hanger Yoke Valve and the PISS
Yoke Assembly has pins for E Cylinders to fit on
Pin Index Safety System
What is the pin index for Oxygen? Nitrous Oxide? Air?
Failure to open cylinder valve will result in no gas flow to anesthesia machine
Hanger Yoke Valve
Acts as a “safety” valve
Minimizes transfilling between cylinders
Opens with pressure and closes with pressure
Considered unidirectional….so what kind of valve is this?
2, 5
3, 5
1, 5
Check Valves  they are unidirectional

11. Cylinder Pressure Gauge
Reflects cylinder pressure
Bourdon Pressure
PSI in tank exerted on small piece of copper that is bent into a curve, sealed and linked to clock like mechanism
The higher the pressure the more it wants to straighten out which then turns the pointer

12. Intermediate Pressure System
Think Pipeline Pressure
Oxygen Second Stage Regulator
Ventilator Power Inlet
Pipeline Inlets, Check Valves, Pressure Gauges
Flow Meter Valves
Oxygen Pressure Failure Devices
Flush Valve
40-50 psi!

13. Oxygen Second Stage Regulator
Located downstream from oxygen supply source
Supplies constant pressure to the oxygen flow control valves regardless of fluctuating line pressures
Reduces oxygen pressure to psi
The pressure shut off VALVES have a higher threshold of psi.
Ensures that oxygen is the last gas flow to decrease if oxygen pressure falls

14. Oxygen Flush Valve
Separate line to flush valve comes from a common source to the hospital pipeline DISS and cylinder yokes
Used for emergency pressurization on circuit when you lose pressure delivery
Remember, it is what type of valve?
Ball and spring type

15. Low Pressure System Flow Meter Tubes Vaporizers Check Valves
Common Gas Outlet
Usually around 16 psi is considered low pressure system

16. Flowmeter Tubes Thorpe Tubes Gas flows range from 200 mL to 15 L
Variable Orifice Design
Larger diameter at top than bottom
The higher the ball/float, the more turbulent the air
Gas flows range from 200 mL to 15 L

17. Flowmeter Tubes (continued)
Series of 2 flowtubes per gas/air
Left hand tube = fine flow tube
Right hand tube = cooarse flow tube
Traditional flowmeters calibrated at atmospheric pressure and room temperature of 20 degrees Celsius
How many “torr” is one atmosphere?
When flowtubes are used at high altitudes, is the actual flow higher or lower than indicated?
1 atm = 760 torr
High altitudes = actual flow is higher than indicated….this is because atm pressure decreases with altitude
At low altitudes, actual flow is lower

18. Common Gas Outlet Most susceptible to leakage
Point of exit for gas from anesthesia machine
A fresh gas entry port/delivery tube through which gases are delivered from the anesthesia machine to the breathing circuit system

19. Vaporizers
Variable Bypass Flow Over Wick Design

20. Vaporizers
Gas/Vapor Blend (AKA Desflurane Vaporizer)

21. Circle System Components
CO2 Absorber
APL Valve
Common Gas Outlet
Reservoir Bag
Inspiration and Expiration Check Valves (Flutter Valves)
Corrugated Tubing with Patient Mask

22. Carbon Dioxide Absorbers
Soda Lime Final Products
Calcium Carbonate
Sodium Hydroxide
Potassium Hydroxide
Water and Heat
Baralyme Final Products
Calcium Carbonate
Barium Hydroxide
Water and Heat
These are final products when CO2 reacts with soda lime….baralyme….
4-8 mesh
Allows rebreathing
Exothermic reaction
What size mesh is considered acceptable for granule size?

23. Other Nuances to Remember
Scavenging System
Link 25 system for hypoxic guard system
Draeger or Ohmeda?
Oxygen Failure Protection Device is NOT an all or none phenomenon
What happens when the vaporizer is tipped then leveled? Will the carrier flow carry more or less agent to the patient?
Scavenging System – receives gas from APL and ventilator; can be passive or active – basically with or without suction
Link 25 – Ohmeda
OFPD – Draeger
More agent to patient

24. Question 1
The devices that prevents reverse flow of gases from the anesthesia machine to the pipeline or atmosphere is:
A. Diameter Index Safety System
B. Check Valve
C. Pin Index Safety System
D. Pressure Gauge
B. A check valve is located downstream from the inlet. It prevents reverse flow of gases from the machine to the pipeline or to the atmosphere.

25. Question 2
All of the following are functions of the check valve EXCEPT:
A. It reduces pressure in the system.
B. It minimizes leakage from an open cylinder to the atmosphere if one cylinder is absent.
C. It minimizes gas transfer from a cylinder at high pressure to one with lower pressure.
D. It allows uninterrupted gas flow from one cylinder to another.
A. Pressure in the system is reduced by pressure-reducing valves. The check valves mainly control the forward flow of gases through the system.

26. Question 3
The component of the anesthesia machine that changes the pressure of an incoming gas to a pressure suitable for use in the anesthesia machine:
A. Safety Valve
B. Pressure Increasing Valve
C. Pressure Regulator
D. Check Valve
C. Each cylinder supply source has a pressure reducing valve known as the cylinder pressure regulator. It reduces the high and variable storage pressure to a lower more constant pressure suitable for use.

27. Question 4 The first stage regulator reduces gas pressure to:
A. 15 psi
B. 60 psi
C psi
D psi
D. The first stage pressure regulator reduces the gas pressures from their high cylinder level to psi. The second stage pressure regulators then reduce the pressure event further for specific gases.

28. Question 5 The second stage regulator reduces O2 pressure to:
A. 45 psig
B psig
C. 10 psig
D psig
B. Second stage regulators reduce O2 pressure to psi. the pressure shut off valves have a higher threshold of psi. this ensures that oxygen is the last gas flow to decrease if oxygen pressure falls.

29. Question 6 Where is the second stage regulator located?
A. At the hanger yoke
B. Just before flowmeter
C. Just after flowmeter
C. The second stage regulator is located downstream from the oxygen supply source. This regulator supplies a constant pressure to the oxygen flow control valves regardless of fluctuating line pressures.

30. References
Nagelhout, J.J. (1999). Review of Nurse Anesthesia. Philadelphia: Saunders.
Nagelhout, J. J. & Plaus, K. L. (2014). Nurse Anesthesia. St. Louis: Elsevier Saunders.
Memory Master: Questions & Answers for the Student Registered Nurse Anesthetist (2012). Valley Anesthesia.
Morgan, G. E., Mikhail, M. S., & Murray, M. J. (2006). Clinical Anesthesiology (4th ed). New York: McGraw-Hill.
Teich, A. & Schaus, S. S. (2014). A Comprehensive Certifying Examination Review Course Manual. Valley Anesthesia Educational Programs.
Wiltse-Nicely KL and Macksey LF. CRNA Certification Exam Review. Jones and Bartlett Learning: Burlington, MA; 2014.

31. Questions?