The anesthesia machine
• Components work together to deliver controlled amounts of oxygen and anesthetic gas
Components of breathing system
• Everything after the common gas outlet o Anesthetic tubing
o Rebreathing bag
o CO2 absorber
o Scavenge system
Functions of breathing system
• To deliver oxygen and anesthetic gas
• To remove CO2 from exhalation
• To facilitate controlled ventilation
Anesthetic systems/circuits
• Circle system or Rebreathing system
o Commonly used in patients greater than 7 kg
• Utilizes inspiratory and expiratory valves as well as CO2 canister
o Closed or partially closed system
• Also called low-flow anesthesia
• Refers to the oxygen flow rate and position of the pop-off valve
• Non-rebreathing system
o Most often used for patients less than 7 kg
The importance of oxygen
• Anesthesia machines are designed to deliver volatile anesthetics in the presence of oxygen: Oxygen is the carrier gas for
anesthetic
o 100% oxygen is commonly used to deliver anesthetics
o This is necessary for the delivery of adequate amounts of O2 to tissues
• Anesthetics reduce tidal volume
• Anesthetics cause some degree of respiratory depression
• It is important to avoid hypoxemia
• Low arterial oxygen concentration
Oxygen cylinders
• Obtained as compressed gas
• Pressurization is necessary to fit a large amount into a relatively small container
• Sizes A-H available, most common are sizes E and H
• Full cylinders contain 2200 psi of gas with varying volumes based on size
o E-cylinders
• Small and easy to carry
• Holds ~ 770 L of oxygen
• Commonly found attached to an anesthetic machine
o H-cylinders
• Huge and heavy
• Holds ~ 7000 L of oxygen
• Commonly found in a closet or chained to a wall
Other medical gases
• All medical gas cylinders are color coded for safety
o Oxygen is green
o Nitrous oxide is blue
o Air is yellow
o Nitrogen is black
• These colors are true in the US only
Pressure regulator
• Provides a safe, constant operating pressure within the machine regardless of the pressure in the tank
