THE ANESTHESIA GAS MACHINE

Karen GarciaN747 Evidence Based Practice for Nurse Anesthesia

Components of the Gas Machine

Valves High Pressure System Immediate Pressure System Low Pressure System Circle System/Breathing Systems

Valves

Free Floating/Check Valves Ball and Spring Diaphragm Valves

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)

“Ball and Spring” Type Valve You supply the energy for this valve! Oxygen Flush Valve

Pressurized at 40-50 psi from wall or cylinder

Oxygen delivered to patient at 35-75 L/minute

May cause barotrauma

Is this considered high, intermediate, or low pressure?

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

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?

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?

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

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?

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

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

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 12-19 psi The pressure shut off VALVES have a higher

threshold of 20-30 psi. Ensures that oxygen is the last gas flow

to decrease if oxygen pressure falls

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?

Low Pressure System

Flow Meter Tubes Vaporizers Check Valves Common Gas Outlet

Flowmeter Tubes

Thorpe Tubes 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

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?

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

Vaporizers

Variable Bypass Flow Over Wick Design

Vaporizers

Gas/Vapor Blend (AKA Desflurane Vaporizer)

Circle System Components

CO2 Absorber APL Valve Common Gas Outlet Reservoir Bag Inspiration and Expiration

Check Valves (Flutter Valves) Corrugated Tubing with

Patient Mask

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

Allows rebreathing Exothermic reaction What size mesh is considered

acceptable for granule size?

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 Draeger or Ohmeda?

What happens when the vaporizer is tipped then leveled? Will the carrier flow carry more or less agent to the patient?

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

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.

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

Question 4

The first stage regulator reduces gas pressure to:

A. 15 psi B. 60 psi C. 20-30 psi D. 45-50 psi

Question 5

The second stage regulator reduces O2 pressure to:

A. 45 psig B. 12-19 psig C. 10 psig D. 45-55 psig

Question 6

Where is the second stage regulator located?

A. At the hanger yoke B. Just before flowmeter C. Just after flowmeter

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.

Questions?