Anesthesia rebreathing apparatus

Abstract

A general anesthesia rebreathing system comprised of a disposable portion adapted to be easily coupled to and decoupled from a permanent portion. The system is designed so as to minimize the structural complexity and cost of the disposable portion while assuring that the disposable portion includes all elements which are likely to contaminate gases inhaled by a patient. The disposable portion includes conventional breathing tubing for coupling a source of fresh gas, as from an anesthesia machine, to a patient and in addition an overflow tube for coupling the patient end of the system to an overflow (pop-off) valve, preferably mounted on the machine and constituting part of the permanent portion. The overflow tube entrance is located close to the patient end of the system and in communication with the tubing which conveys expired gas to a reservoir, such as a conventional breathing bag, mounted at the machine end. The arrangement assures that the patient's initially expired dead space gas is conveyed by the tubing to the reservoir with subsequently expired alveolar gas being exhausted through the overflow tube and pop-off valve. By preferentially exhausting alveolar gas in this manner, the need for using CO.sub.2 absorber material within the system is minimized. The use of an overflow tube as described, to preferentially exhaust alveolar gases is applicable to both circle and single tube anesthesia rebreathing systems. The reservoir can be squeezed to assist the patient' s breathing, either manually by the attending anesthetist or mechanically by a machine commonly known as a ventilator. For optimum performance, the pop-off valve is operable in two different modes, i.e. (1) as a manually controlled variable orifice and (2) as an automatically controlled valve responding to a positive control pressure. The source of control pressure is selectable by the attending anesthetist dependent on the type of ventilation being employed, i.e. spontaneous, manually assisted, or mechanically controlled. In order to isolate the ventilator from the patient's gas, the reservoir preferably comprises a container formed by a flexible outer wall containing a flexible septum therein defining two isolated chambers. The ventilator communicates with one chamber and the other chamber communicates with the anesthesia system tubing. As the ventilator pressurizes the first chamber, the flexible septum between the chambers transmits the pressure to the other chamber and thereby to the patient's airway.

Dependencies are inferred from the claim text.