Proof of Concept for Ozone-Based Disinfection of Heater Cooler Units

Abstract

Heater Cooler Units (HCUs) are frequently used not only during heart surgery but also in ECMO therapy to regulate the blood temperature of patients. It is known from cardiac surgery that the water circuits of HCUs can be bacterially contaminated and under adverse conditions can lead to a nosocomial infection of the patient. The addition of chemical disinfectants to the water of HCUs is problematic. In addition, it is an increasingly significant cost factor due to the required material and personnel input. The aim of this research project is both the development of an automated device for disinfecting water in HCUs and proof of its effectiveness. The device is based on ozone, a substance with known antimicrobial properties. To prevent ozone from coming into contact with the HCU components, the water is irradiated with UV light (254nm). Two bypasses and ozone sensors guarantee a complete elimination of residual ozone. The effectiveness of the device was tested by series of experiments with the surrogate germ, Pseudomonas aeruginosa. The device allows a wide range of ozone concentrations and exposure times to be selected. In previous test series, it has been shown both that a reduction of the bacterial count to drinking water quality can be achieved with a treatment time of only one hour, and that self-cleaning can be carried out effectively before clinical use, and in standby mode. Attention must be paid to the water quality in HCUs as a potential source of infection, regardless of where they are used. The "proof of concept" showed an excellent disinfection effect with simultaneous elimination of excess ozone to drinking water levels. The number of indicator bacteria in the water tank of the dummy HCU was reduced by approx. 98% after only 30 minutes.

Keywords

• heater cooler unit
• disinfection
• ozone
• ecmo
• mycobacterium chimaera
• computational fluid dynamics
• experimental rig “o3desi”