DEVELOPMENT AND ASSESSMENT OF A NEW SOLUTION FOR CARBON DIOXIDE REMOVAL FROM ANAESTHESIA REBREATHING CIRCUITS

Abstract

Background: Our aging population’s rising health care costs cannot be met by the limited numbers of young tax payers. Compounding the cost of surgery are the costs associated with post operative cognitive decline (POCD) that up to 80% of patients experience. Currently, chemical absorbers are mandatory for most anaesthesia procedures yet the resultant by- products are known to contribute to the incidence of POCD. Approach: This thesis presents a unique approach for a new dense skin poly-methyl-pentene (PMP)membranebasedCO2filter. Theobjectiveistheeliminationofchemicalabsorbers’ contributiontoPOCDinanaesthesia. Themainchallengeofthisapplicationistheexclusion of active components for improved CO2 removal. Such a passive system is key for fast regulatory approval and adoption in anaesthesia practice. Methods: First, the continued need for CO2 removal is confirmed in a literature review. Second, the optimization of a custom PMP hollow fibre membrane for CO2 removal and anaesthetic vapour selectivity is successfully demonstrated. A unique characterization approach guided the optimization. Third, an application module is modeled and prototypes are built using the optimized custom membrane. Applying membrane system theory, CO2 removal performance is further optimized; developing a unique double-pass sweep flow arrangement. Fourth,theprototypesareverifiedforthesafeusein-vivoinanimalandhuman studies. Fifth,patientventilationcasesaredemonstratedusingdatarecordedattheNova Scotia Health Authority. These cases are used in conjunction with a unique dynamic system model to optimize the design based on the trade-off between surface area and sweep gas use. The predictions are verified in a bench setup using an anaesthesia machine ventilating a lung simulator with CO2 feed. Results & Conclusion: It was shown that (i) CO2 removal in anaesthesia is required in the future (not replaced by TIVA), (ii) the membrane and system could be optimized for minimal surface area and sweep flow, (iii) such passive membrane systems can match or exceed the performance of chemical absorbents. This confirms that PMP membranes can safely replace chemical absorbents, thus eliminating the contribution to POCD. A clinical study is recommended for the final validation of these study results.