• S Inoue, T Sakamoto, K Kitaguch, and H Furuya.
• Department of Anesthesiology, Nara Medical University, Nara, Japan.
• Acta Anaesthesiol. Sin. 2000 Jun 1; 38 (2): 85-8.

AbstractAn anaesthesia ventilator of to-and-fro type incorporated into the anesthesia machine was used for mechanical ventilation in a patient undergoing plastic surgery under sevoflurane anaesthesia. During operation, elevation of blood pressure and tachycardia, which suggested inadequate anesthesia could not be managed by adjustment of sevoflurane to higher concentrations. However, the patient's lungs could be well ventilated without problems. Close to the end of anaesthesia, a disconnection at the mixed gas common outlet before the check valve of anaesthesia machine was detected. The patient could recall and recount all the happening during the operation signifying that he was not sufficiently anesthetized. In the case that the fresh gas supply line before the check valve is disconnected, the lungs can still be ventilated if a to-and-fro type of ventilator is used. Because there is no leakage of gas from the check valve every bit of the gas which drives the ventilator begins to work and deliver a flow of gas sufficiently to maintain a tidal volume. As a result, anaesthetic gas is replaced by a driving gas. A ventilator of to-and-fro type is still used in clinical anesthesia due to its simple design. The phenomenon reflects the pitfall in the design of a to-and-fro type anaesthesia ventilator.

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