Ca(OH)2 CO2 absorbents: Performance, cost, and environmental effect

A lot has changed ever since the invention of ventilators to save patients with respiratory compromise due to polio. Different ventilators configurations required high fresh gas flows to avoid rebreathing expired CO2. With the introduction of inhaled anesthetics and the associated cost, a new mean was required to enable rebreathing the anesthetics to decrease the cost while removing the CO2 from the breathing circuit. Hence, the introduction of soda lime as a CO2 absorbent in the anesthesia machine. The main component of the soda lime that absorbs the CO2 is calcium hydroxide, other components play role as catalysts to help speed up the absorption of CO2. The chemical reaction is described as: CO2 + Ca(OH)2 → CaCO3 + H2O + heat There are a lot of claims from different companies regarding the efficiency of their product, performance and real cost. Most, if not all, previous work trying to compare these products were small studies, not comprehensive, with no consistent definitions, and variable benchmarks to compare these products. In part one of this PhD project, I will start with defining the efficiency and find a practical way to measure it. I will run an experiment in which I will measure the maximum absorption capacity of different CO2 absorbents. In part twee I will compare the performance of all commercially available soda lime products in vitro under controlled condition. 4 different anesthesia machines will be used, since not all products are available for all machines, namely the ADU (which will be used to compare all loose fill products plus pre-packed that are not available in loose fill packing), Aysis, Zeus and the Flow-i (which will compare pre-packs only). The same protocol will be applied on all machines. This data will be also used to complete part one by calculating the efficiency of the products. In part three I will validate the data collected from in vitro experiments by testing some of these CO2 absorbents products in vivo, mainly with the Flow-I and the Aysis. Lastly, after validating the in vitro data, it will be used to build up a cost model to get an idea of the real cost of some of these products, and I will run an example from data from UZ Leuven.