Breathing circuit

Breathing Circuit

A breathing circuit is a medical device used to deliver oxygen, remove carbon dioxide, and deliver inhalational anaesthetic agents to a patient. It is commonly used in anesthesia and intensive care medicine.

History

The concept of a breathing circuit was first introduced in the late 19th century by Arthur Guedel and Ralph Waters. They developed the Guedel-Waters circuit, which was the first closed system for delivering anesthesia.

Types of Breathing Circuits

There are three main types of breathing circuits: open, semi-open, and closed.

Open Breathing Circuits

In an open breathing circuit, fresh gas flows directly from the source to the patient. There is no rebreathing of exhaled gases. Examples include the Bain circuit and the Jackson-Rees circuit.

Semi-Open Breathing Circuits

In a semi-open breathing circuit, some of the exhaled gases are rebreathed by the patient. This is achieved by using a reservoir bag. Examples include the Mapleson circuit and the Magill circuit.

Closed Breathing Circuits

In a closed breathing circuit, all of the exhaled gases are rebreathed by the patient. This is achieved by using a carbon dioxide absorber. Examples include the Circle system and the Waters' to-and-fro system.

Components of a Breathing Circuit

A typical breathing circuit consists of several components, including a fresh gas flow source, a patient interface, a reservoir bag, a carbon dioxide absorber, and various valves and tubes.

Fresh Gas Flow Source

The fresh gas flow source provides a continuous supply of oxygen and inhalational anaesthetic agents. It is typically connected to a central gas supply or a portable cylinder.

Patient Interface

The patient interface is the part of the circuit that connects to the patient. It can be a face mask, a laryngeal mask, or an endotracheal tube.

Reservoir Bag

The reservoir bag stores fresh gas and allows the patient to rebreathe some of the exhaled gases.

Carbon Dioxide Absorber

The carbon dioxide absorber removes carbon dioxide from the exhaled gases before they are rebreathed by the patient.

Valves and Tubes

Various valves and tubes are used to control the flow of gases and to prevent the rebreathing of carbon dioxide.

See Also

• Anesthesia machine
• Mechanical ventilation
• Respiratory therapy

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