The ins and outs of the anesthesia machine (Proceedings)

Apr 01, 2009

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