| 摘要 |
In anaesthetic apparatus comprising an evaporator with a by-pass, each branch incorporates a valve or restriction both of which have the same resistance characteristics with change in gas velocity. Preferably an adjustable cone valve is used, in each branch, in which the ratio of the width of the annular passage to the length of the cone is less than 10-2 for all possible open positions of the valve. With this arrangement the ratio of mixture proportions remains substantially constant irrespective of the rate of total flow. |
