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Understanding the Common Gas Outlet on Anesthesia Machines

Anesthesia machines combine gases such as oxygen with anesthetic agents to sedate patients and help them breathe during complex procedures. They deliver this mixture via the common gas outlet (CGO), which connects to the breathing circuit and, in turn, to the patient’s respiratory system.

 

The CGO ensures a controlled, properly measured flow of gas, keeps patients breathing, and helps them remain comfortable. It also facilitates the machine’s oxygen flush during emergency situations.

 

As the CGO is paramount for patient safety, it must be properly maintained and serviced on a regular basis with your standard anesthesia machine maintenance. Let’s learn more about the common gas outlet on anesthesia machines, their notable issues and how to source reliable components when they need repairs. 

 

What is the Common Gas Outlet (CGO)?

The CGO is the passageway through which all the anesthetic machines' gases travel. It’s generally a piece of metal pipe sticking out from the rear of the anesthesia machine near the back bar. It features a threaded connector onto which you can screw the device’s breathing circuit.

 

The CGO itself doesn't produce gases like other anesthesia machine parts. It works instead as the primary delivery mechanism. Generally, three kinds of gas pass through the CGO:

 

  • Oxygen – Oxygen is vaporized in tanks and mixed with anesthetic agents to help patients breathe during long procedures. If there’s an issue with the chemical composition the patient is breathing, the CGO can also flush the breathing circuit with oxygen to prevent any further problems.

 

  • Nitrous oxide – Nitrous oxide produces both anesthetic and analgesic effects when inhaled medically.

 

  • Anesthetic agents – Exact agents vary depending on the patient’s needs and the specifics of the procedure.

 

In essence, the CGO supplies everything the patient inhales while under anesthesia. It works in tandem with the device’s other flowmeters, pressure regulators, and other mechanical components to ensure a steady fresh gas flow at all times.

Key Safety Features of the Common Gas Outlet

Because the CGO is responsible for delivering anesthetic gases, built-in safety features ensure correct operation and prevent hazards:

  • Check valve – Prevents reverse flow of gas, reducing the risk of contamination.

  • Hypoxic guard system – Ensures that the oxygen percentage never drops below safe levels, preventing a hypoxic mixture.

  • Gas flow monitors – Track oxygen flow and nitrous oxide levels, alerting clinicians to potential failure or leaks.

  • Automatic shutoff – In case of pipeline failure, the system prevents unsafe gas mixtures from being delivered.

Proper CGO maintenance and testing ensure these safety features function correctly to protect patients.

 

How the Common Gas Outlet Works

Anesthesia machines are complex devices split into multiple chambers of different pressures. Within these compartments are various components—including the ventilator, vaporizer, and other parts. These pieces work together to turn liquid chemicals, such as oxygen and anesthetic agents, into breathable gases.

Pressure Systems in the CGO

The CGO operates within a defined pressure system, categorized as:

  • High pressure – Gases from a cylinder are stored at high psi levels and pass through a pressure regulator to reduce pressure before reaching the patient.

  • Low pressure – Once gases reach the CGO, they are in a controlled low-pressure state, ensuring precise delivery to the breathing circuit.

Since nitrous oxide and oxygen have different supply lines within the anesthesia machine, they don’t mix until they reach the CGO. Therefore, the CGO delivers a tempered flow of both gases to provide the right composition to patients.

 

CGOs are versatile components that are compatible with a variety of breathing circuits, including:

 

  • Closed circuits – Closed breathing circuits rely entirely on rebreathing to supply oxygen to your patients—meaning they remove carbon dioxide before returning air to the CGO.

 

  • Semi-closed circuits – Semi-closed circuits feature some rebreathing—meaning they neutralize carbon dioxide—but also incorporate fresh air to supply the patient with sufficient oxygen.

 

  • Open circuits – Open circuits don’t feature rebreathing or carbon dioxide neutralization—meaning patients derive their oxygen externally rather than from the machine.

 

Common Issues with the Common Gas Outlet

The CGO is a key component of your anesthesia machine and is always in use. To keep it in safe, operational shape and minimize your anesthesia machine repair bills, routinely check your CGO for:

 

  • Blockages – Any debris that enters the CGO can impede gas flow—potentially leading to the wrong chemical composition being delivered to your patients.

 

  • Leaks – Slits and holes can reduce your anesthesia machine's efficiency and cause it to run at the wrong pressure, which can lead to further problems later on. 

 

  • Improper connections – A loose or broken connection or seal acts like a leak, causing gas to escape and altering your machine's operating pressure.

 

  • Wear and tear – Other noticeable signs of wear—such as rust, chips, or worn-out threading—should be addressed and remedied as soon as possible. 

Testing and Maintenance for Common Gas Outlets

Regular CGO testing ensures safe operation and compliance with medical standards. Common procedures include:

  • Leak tests – Checking for gas leaks within the CGO assembly, breathing circuit, and pipeline.

  • Flow rate verification – Ensuring flowmeters are delivering the correct gas mixture and oxygen concentration.

  • Check valve functionality – Verifying that the check valve prevents backflow and contamination.

  • Oxygen flush test – Testing the oxygen flush valve to confirm it delivers emergency oxygen flow at the correct rate.

Proactive CGO maintenance prevents unexpected failures and ensures seamless gas delivery in the operating room.

 

Sourcing Reliable Common Gas Outlets

Since CGOs provide the very pathway through which anesthetized patients breathe, they must be in optimal shape to support clinical safety. 

 

If your CGO breaks down, replace it with compatible, high-quality parts from a trusted source. 

 

PartsSource is America’s go-to supplier for all anesthesia components—from breathing circuits to vaporizers and, of course, CGOs. You must use genuine Original Equipment Manufacturer (OEM) and reliable aftermarket parts to comply with medical safety standards and promote patient safety. Get them straight from the source—PartsSource. 

 

Find Reliable Replacement CGOs and Other Anesthesia Machine Parts at PartsSource 

The common gas outlet on anesthesia machines (the CGO) mixes oxygen and anesthetic gas before delivering it to the patient’s breathing circuit. It’s crucial to keep your CGO in operating shape to ensure patient safety and avoid costly repairs. Inspect your CGO for signs of wear and tear regularly, and if there’s an issue, replace it with genuine parts from PartsSource.

 

Whether you need a new CGO or any other component, PartsSource has top-of-the-line replacement parts for anesthesia machines and a variety of other medical devices. When your equipment breaks down, lean on PartsSource for quick service, expert advice and the best parts around. 

 

Sources: 

 

University of Bristol. Anesthesia Machine Anatomy. https://www.bristol.ac.uk/media-library/sites/vetscience/documents/clinical-skills/Anaesthetic%20Machine%20Anatomy.pdf. 

 

National Library of Medicine. The Basic Anaesthesia Machine. https://pmc.ncbi.nlm.nih.gov/articles/PMC3821260/. 

 

National Library of Medicine. Nitrous Oxide and the Inhalation Anesthetics. https://pmc.ncbi.nlm.nih.gov/articles/PMC2614651/. 

 

National Library of Medicine. Anesthesia Breathing Systems.. https://www.ncbi.nlm.nih.gov/books/NBK574503/.