Average and longest expected treatment times for ultraviolet light disinfection of rooms

• Published in: American journal of infection control Vol. 50; no. 1; pp. 61 - 66
• Main Authors: Dexter, Franklin, Birchansky, Bradlee, Epstein, Richard H., Loftus, Randy W.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2022
• Subjects: Coronavirus disease 2019 (COVID-19); Disinfection; Humans; Log-normal distribution; Operating room management; Operating Rooms; Patients' Rooms; Prediction limits; Ultraviolet disinfection; Ultraviolet Rays; Weibull distribution; Ultraviolet disinfection; Prediction limits; Log-normal distribution; Weibull distribution; Operating room management; Coronavirus disease 2019 (COVID-19)
• ISSN: 0196-6553; 1527-3296
• DOI: 10.1016/j.ajic.2021.08.020

•We studied treatment times of ultraviolet disinfection with a 3-tower system.•When scheduling time for ultraviolet disinfection, categorize by the room.•Proportional variabilities of treatment times by room are like those of surgical procedures.•Longest treatment times can be estimated using non-parametric 90% prediction limits.
Planning Ultraviolet-C (UV-C) disinfection of operating rooms (ORs) is equivalent to scheduling brief OR cases. The study purpose was evaluation of methods for predicting surgical case duration applied to treatment times for ORs and hospital rooms.
Data used were disinfection times with a 3-tower UV-C disinfection system in N=700 rooms each with ≥100 completed treatments.
The coefficient of variation of mean treatment duration among rooms was 19.6% (99% confidence interval [CI] 18.2%-21.0%); pooled mean 18.3 minutes among the 133,927 treatments. The 50th percentile of coefficients of variation among treatments of the same room was 27.3% (CI 26.3%-28.4%), comparable to variabilities in durations of surgical procedures. The ratios of the 90th percentile to mean differed among rooms. Log-normal distributions had poor fits for 33% of rooms. Combining results, we calculated 90% upper prediction limits for treatment times by room using a distribution-free method (e.g., third longest of preceding 29 durations). This approach was suitable because, once UV-C disinfection started, the median difference between the duration estimated by the system and actual time was 1 second.
Times for disinfection should be listed as treatment of a specific room (e.g., “UV-C main OR16”), not generically (e.g., “UV-C”). For estimating disinfection time after single surgical cases, use distribution-free upper prediction limits, because of considerable proportional variabilities in duration.