The most common respiratory circuitry of anesthesia is the circulatory system. Two one-way valves allow gas to flow into a loop that absorbs carbon dioxide by chemical methods. In this system, fresh gas from the anaesthetic machine enters the respiratory circuit at the downstream part of the carbon dioxide absorbing tank and the upstream part of the valves. The incoming fresh gas mixes with the original gas in the loop system, flows through the suction unidirectional valves, and reaches the Y-shaped tube through a reusable or disposable corrugated pipe. The patient's exhaled gas flows through another branch of the circulatory system (exhale) and enters the airbag through a one-way valves. By squeezing, the airbag produces positive pressure, forcing the collected gas through the carbon dioxide absorption device. Because fresh air flowing into the loop system is much more than the amount of gas consumed by the patient and the absorbent, one such safety valve must be installed between the expiratory unidirectional valves and the carbon dioxide absorbing tank. Excess gas can escape when the pressure exceeds the specified threshold. A mixture of soda lime (sodium, potassium and calcium hydroxide) or a mixture of barium hydroxide (barium hydroxide, eight hydrogen hydrate and calcium hydroxide) is contained in the absorption tank. These substances absorb carbon dioxide through chemical reactions, releasing heat and water (releasing water that can moisten the air in the circulatory system). When the absorptive capacity is depleted, the indicator changes color. The absorption tank must be designed to facilitate the replacement of absorbent. The APL valve used for discharging too much gas is usually a spring load valve. Spring tension is the control of the loop pressure, if the patient spontaneously breathing, the safety valve is in the open position, breathing with minimal resistance to inhale and exhale air.
After anesthesia induction, the patient connects the air anaesthetic machine with a closed mask or a tracheal catheter. When inhaling, the anesthetic mixture gas is valves into the patient's body by an open suction, and the exhale valves open while inhaling the valves off and exhaling the exhaled gas. Folding bellows can be used when using auxiliary or controlled breathing. Inhale and press down, exhale and pull up to ensure that the patient has adequate ventilation. At the same time, according to actual needs, adjust the ether switch to maintain a stable level of anesthesia.
The disadvantage of this device is that the ether concentration is low, only as the maintenance of anesthesia, and the consumption of ether is large, easy to cause environmental pollution.