Are your endoscope channels dry? Development of a novel liquid detection method using humidity readings in an enclosed vessel.

BACKGROUND

Endoscope drying is essential to prevent outgrowth of waterborne organisms during storage and to set the stage for effective gaseous sterilization. However, there are currently no comprehensive approaches for verifying dryness.

METHODS

An air test system was developed to determine the efficacy of a liquid detection method. Detection consisted of a vessel containing a humidity sensor that captured and measured air as it exited endoscope channels. The input-air parameters were controlled to determine the impact on detection in channels by recording the change in humidity as the channels dried. A design of experiments (DOE) was performed with 'dry' (≤1% relative humidity [RH]) or 'wet' (≥30% RH) air delivered at constant pressure and flow rate to endoscope channels (1.7-mm, 4.2-mm and 6.0-mm inner diameter) containing either 0, 0.5 or 1 mg of water or alcohol. A second DOE was performed in test articles to determine the impact of the flow rate, pressure and connection configuration on the method's sensitivity. Follow-up testing was conducted to verify the method's sensitivity in operational endoscopes.

FINDINGS: There was a statistically significant difference between detection of 0 mg (dry) and 0.5 or 1.0 mg. The method's sensitivity was confirmed within operational endoscopes when optimal parameters were applied.

CONCLUSION

A method has been developed that assesses whether endoscope channels contain liquid. Further refinement of this method may support validation of manufacturer drying instructions and end-user drying verification.