Anesthesia Breathing Circuit
failures are extremely rare. However, there have been 13 reported cases of failure in the past four years. Failures occurred during the placement of the circuit tubing in the tube tree holder and during the repositioning of the patient's head. All patients who had suffered circuit failures were rescued using an alternate respiratory circuit. While most failures occurred during the repositioning phase, some occurred at critical times.
The most common type of anesthesia breathing circuit is the King circuit, which is the same circuit as used during cardiac surgery. Other systems include the Mapelson D system and the Bain system, but these are inefficient for spontaneous ventilation and require high gas flows. The Mapelson D circuit is also less bulky than the Bain system and provides more humidification and heat to inspired gases. The two systems have their own differences, however.
The Mapleson D and Bain NRB circuits have similar components, but are coaxial. The Bain circuit is a variation on the Mapleson D and Bain NRB circuits. The Bain circuit requires the same components, but directs fresh gas flow tubing within the inspiratory limb. These circuits have been shown to add more heat and humidity to inhaled gases. The diagram below illustrates how they work.
The main component of an anesthesia breathing circuit is a mask that connects the patient to the machine. This mask connects to the patient's airway, the inspiration tube, and the expiration tube. Then, the patient wears a mask or larynggeal mask. Ultimately, these two tubes form the breathing circuit. Regardless of the type, an anesthesia breathing circuit is essential for the patient's safety.