Authors (including presenting author) :
Leung CK(1), Ng WS(1), Yau TY(2), Lee CC(2), Yuen KC(3), Ko SM(1)(3), Yeung WC(2), Lee CK(1)(2)(3)
Affiliation :
(1) Sterile Services Department, Pok Oi Hospital
(2) Sterile Services Department, Tuen Mun Hospital
(3) Sterile Services Department, Tin Shui Wai Hospital
Keyword 1: :
Thermal Disinfection
Keyword 2: :
Conductivity
Keyword 3: :
Chemical Residue
Keyword 4: :
RO Treatment
Introduction :
Water quality is crucial at various stages of medical device reprocessing, especially during thermal disinfection. Poor water quality can adversely impact medical devices, the process and potentially lead to patient infections or pyrogenic reactions. In NTWC Sterile Services Departments, water used for thermal disinfection undergoes reverse osmosis (RO) treatment to remove chemical contaminants, organic material, endotoxins and microorganisms. Conductivity serves as a critical indicator for monitoring the RO system performance and checking for residual detergents from prior cleaning stages, as it measures the concentration of electrically charged impurities. According to ANSI AAMI ST108:2023, conductivity for incoming final rinse water should below 10μS/cm, while detergent supplier guidelines specify a maximum tolerable residue limit of 25 μS/cm in processed rinse water. Traditionally, conductivity is assessed by manual sampling during disinfection, but this method has notable drawbacks. This study introduces a new approach for real-time monitoring of final rinse water conductivity in washer disinfectors.
Objectives :
To develop a routine workflow for monitoring the conductivity of critical water during thermal disinfection in washer-disinfectors.
Methodology :
A conductivity sensor was installed inside the washer disinfector chamber for real-time monitoring. A remote transmitter was placed next to the washer disinfector’s monitor to record measurements when the disinfection stage was identified. Additionally, a conductivity pocket tester was used to measure water samples taken from the side door. The measurements from both devices were compared for accuracy.
Result & Outcome :
A strong correlation (r2= 0.8719) was found between the built-in conductivity meter and the pocket tester, confirming the reliability of continuous monitoring. Utilizing the washer’s built-in conductivity meter provides a reliable, cost-effective means of ensuring water quality compliance. By eliminating manual sampling, it reduces staff exposure to 90°C heat and steam hazards. Staff can continuously monitor the real-time conductivity data over a 5-minute disinfection period directly on the control panel, while the pocket tester may struggle with sample homogeneity and produce inaccurate results. Routine calibration and standardized protocols further ensure adherence to AAMI/supplier thresholds, safeguarding the sterility and longevity of medical devices.
