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GARY

Carbon Dioxide Absorber

Carbon dioxide absorbers do just that - absorb CO2. In turn, they allow rebreathing of all other gases except CO2. The most commonly used bases in absorbers are sodium hydroxide, potassium hydroxide, and calcium hydroxide. Some manufacterers may only use one, or they may use a comination of all three.

Inspiratory & Expiratory Limbs

The inspiratory limb carries oxygen and volatile anesthetics to the patient. The expiratory limb carries oxygen, volatile anesthetics, and carbon dioxide away from the patient.

Inspiratory & Expiratory Unidirectional Valves

These valves control which way gases flow. In both valves, "... a light, thin disc seats horizontally on an annular seat" (Dorsch, 2011, p. 141). During inspiration, the inspiratory valve is open and the metal disc rises to allow gases pass. At the same time, the expiratory valve is closed. The reverse is true as well; during expiration the expiratory valve is open and the metal disc rises.

The volatile anesthetic travels into the inspiratory limb and then inside of Gary's lungs to be diffused! Gary is happy.

Scavenging System

The purpose of the scavenging system is to collect excess gases from the AGM or exhaled by the patient and removing them to an appropriate place outside the operating room. Active systems use a vacuum and a waste anesthesia gas (WAG) line to vent the gases to the atmosphere instead of inside the OR. Passive systems do not use a vaccum.

• It is not technically part of the breathing system.

Reservoir Bag

The reservoir bag has the most compliance in the breathing system. It functions by gathering expiratory gases that can be used for inspiration, protects the patient from too much pressure, and can be used to help ventilate the patient (Dorsch, 2011).

• The pressure range on a 3L reservoir bag is 35-60cmH2O.

The volatile anesthetic then finds its way into the inspiratory unidirectional valve. With increased pressure, the disc rises up to let them out.

Fresh Gas Inlet

Fresh gas is delivered into the circle system from the common gas outlet via the fresh gas inlet. Sometimes the flexible tubing is visible, but often it is internal to the machine.

Adjustable Pressure-Limiting Valve

"The APL valve is the only gas exit from a breathing system unless a ventilator is being used" (Dorsch, 2011, p. 117). It is used during manual ventilation mode. The APL valve has a disc inside of it that is spring-loaded. When the pressure in the system is too much, the disc rises up and lets the extra gas out. The pressure will decrease and the disc will return to its seat.

Now this is where things can get a little tricky. The volatile anesthetic can end up in a few different places. It could end up in the reservoir bag, waiting for Gary's next inspiration. It could end up around the APL valve, but if there is too much pressure, it's getting out of there and into the scavenging system, where it will be let out into the operating room or in the atmosphere. Or it can pass right on through to the CO2 absorber

The volatile anesthetic starts as a liquid. It then gets vaporized and follows oxygen out of the vaporizer and in to the fresh gas inlet.

If the volatile anesthetic makes it through to the CO2 absorber, it does not get absorbed. It plays a game of Plinko with the absorbent granules and gets out to end up in the same route it entered in to.

The volatile anesthetic makes it out of Gary, travels down the expiratory limb, eventually making it to the expiratory unidirectional valve. The pressure rises again, making the disc rise up from its seat, and lets the volatile anesthetic out.