Possible Alternatives to Soda Lime

It is difficult to classify methods of removing carbon dioxide (C0 2 ) from expired air.Many methods are possible.Some are impractical at present but rapid advances are being made in the fields of aviation, space, underwater and environmental medicine and those methods currently regarded as far-fetched may become accepted within a few years.One way of classifying methods of CO 2 removal is to divide them into: (a) non-regenerative, removing CO 2 alone; (b) non-regenerative, removing CO 2 and supplying oxygen (0 2 ); (c) regenerative, removing CO 2 ; (d) regenerative, removing CO 2 and producing O 2 , Another way is to classify compounds used to remove CO 2 into: 1. absorbents 2. adsorbents (a) carbonaceous adsorbents (b) liquid film sorbents (c) zeolite molecular sieves 3. biogenerators 4. other.Both classifications will be used in this article to clarify the present position in the midst of ongoing research by industry and in other fields of medicine. (a) Non-regenerative methods of CO 2 removalSolid absorbents include sodium, potassium, calcium, barium and lithium hydroxide which have all been used in rebreathing systems.Adsorbents include charcoal and other carbonaceous materials.Liquid and deliquescent absorbents are not used in anaesthesia or in personal portable rebreathing systems owing to the risk of caustic liquid entering and damaging the lungs.Anaesthetists use soda lime and barium lime to absorb CO 2 , Charcoal and Carbosieve also adsorb hydrocarbons, halogenated hydrocarbons and other *EEA.(S.A.), ER.C.