EFFECTS OF HALOTHANE, ETHER AND CYCLOPROPANE ON RESPIRATION

Dogs have been anaesthetized with halothane, ether and cyclopropane,and the depth was kept constant at any desired level by maintainingan unvarying gas concentration in alveolar air. Under thesesteady-state conditions carbon dioxide response curves havebeen elicited at different depths of anaesthesia. All threeanaesthetic drugs caused a progressive reduction of ventilationvolumes as the concentration was increased. In one subject therewas an augmentation of ventilation at moderate levels of etheranaesthesia. Halothane, ether and cyclopropane all producedapnoea at an alveolar concentration approximately 2.2 timesthe minimum concentration required to maintain surgical anaesthesia. ^*Author's present address: Department of Anesthesiology, AmericanUniversity of Beirut, Lebanon.     

REBREATHING IN A DOUBLE T-PIECE SYSTEM

A double T-piece paediatric system is described. During spontaneousrespiration, the system will perform like a Magill system ifthe fresh gas flow is delivered via the distal T-piece; theproximal T-piece will provide an outlet. During controlled ventilationthe set will perform like a Rees system if the fresh gas flowis delivered via the proximal T-piece; the distal T-piece willprovide a control outlet. As judged by the degree of rebreathing,distal inflow is more efficient than proximal inflow duringspontaneous respiration. Distal and proximal inflow are equallyefficient during controlled hyper-ventilation.