Are endotracheal tube, laryngeal mask airway (LMA), and King airway examples of closed systems?

• A. No
• B. The devices are not related to system type
• C. Only ET tube
• D. Yes

Answer: (D)

The main idea here is what constitutes a closed ventilation system. A closed system means the patient breathes through a sealed path that is connected to a ventilator or anesthesia machine, so gases flow in and out through a contained circuit rather than mixing freely with room air.

An endotracheal tube does this by placing a cuff inside the trachea. When the cuff is inflated, it seals the tracheal lumen, and the tube connects to a breathing circuit. This creates a continuous, enclosed pathway for inspired and expired gases, with most of the gas exchange happening within that closed loop.

A laryngeal mask airway forms a seal around the laryngeal inlet with an inflatable cuff. Once connected to a ventilation circuit, gas delivery and removal occur within that circuit, making ventilation largely a closed process despite the device not apposing the trachea as tightly as an endotracheal tube. Some minor leaks can occur around the seal, but the system remains enclosed relative to the room.

The King airway works similarly as a supraglottic conduit with its own seal, allowing ventilation through the connected circuit in a largely closed manner. Again, the critical factor is the sealed pathway provided by the device when attached to a ventilator circuit.

If any of these devices is used without a sealed circuit, or if there’s a cuff leak or disconnection, the setup can become open to the environment. But when they’re used with a proper ventilator circuit, they exemplify closed systems because they keep the inspired and expired gases within a controlled, enclosed pathway.