The Hafnia A Circuit: A Valveless Non‐palluting Anaesthetic System

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Abstract
An anaesthetic circuit is described, which fulfils the following requirements: 1) It is suitable for patients of all age groups; 2) There is no expiratory resistance; 3) There is no anaesthetic gas exposure risk to operating room staff; 4) The change from spontaneous to controlled respiration can be made without the necessity of access to the patient attachment; 5) It is easy to handle and clean.The system is a modified Magill circuit, consisting of a corrugated tube with breathing bag, relief valve, and dumping valve. Gas evacuation is performed continuously through an ejector flowmeter connected to a narrow branch tube at the patient attachment.The flow requirement was calculated by analyses of the system and was investigated using 10 conscious volunteers (spontaneous respiration) and five anaesthetized patients (controlled respiration). Significant rebreathing was not seen with a fresh gas flow exceeding the basal respiratory minute volume requirement by 35%.