To the Editor —Cleaning and disinfection of operating room (OR) surfaces is generally recognized as an important practice, ^{Reference Calderwood, Anderson and Bratzler1–Reference Loftus, Brindeiro, Loftus, Brown, Charnin and Dexter4} although the impact on patient outcomes is uncertain. ^{Reference Xie, Sax and Daodu5} A recent systematic scoping review concluded that the existing literature shows suboptimal compliance and inconsistent effectiveness of OR cleaning and disinfection. ^{Reference Xie, Sax and Daodu5} Ultraviolet-C (UV-C) light room decontamination devices have been shown to reduce surface contamination when operated as an adjunct to manual cleaning and disinfection. ^{Reference El Haddad, Ghantoji and Stibich6} However, use of these devices can require a substantial amount of time and the devices can only be operated when people are not present. ^{Reference El Haddad, Ghantoji and Stibich6} Far-UV-C light (200–230 nm) is an alternative technology that may provide similar efficacy while being safe in occupied areas. ^{Reference Memic, Torres-Teran, Cadnum and Donskey7} Here, we evaluated the efficacy of a commercial, ceiling-mounted far-UV-C technology for continuous adjunctive decontamination of surfaces in a simulated OR.

The Visium 1 far-UV-C technology (Lit Thinking, Orlando, Florida) that was tested uses a krypton-chloride excimer lamp (Care222, Ushio America, Cypress, California) that emits a primary wavelength of 222 nm. We tested the Clear Optics version of Visium 1 which emits light over 60-degree angles. With Clear Optics devices placed a minimum of 1.2 m (3.9 ft) apart and operating continuously at a height of ≥2.5 m (8.2 ft), far-UV-C doses are within threshold limit values proposed by the American Conference of Governmental Industrial Hygienists (ie, 161 mJ/cm² for eyes and 479 mJ/cm² for skin) over an 8-hour workday. ^{Reference Memic, Torres-Teran, Cadnum and Donskey7} Users can also choose an “occupied off” mode in which the device runs continuously but turns off when motion is detected, thereby providing decontamination between cases with no far-UV-C exposure to personnel. Each device is intended to provide far-UV-C coverage for an area up to 18.6 m² square meters (200 ft²); multiple devices can be installed to provide coverage for larger rooms. The supplementary material provides detailed information on the technology and shows results of initial laboratory testing demonstrating efficacy of a single device against methicillin-resistant Staphylococcus aureus (MRSA) with 2 and 8 h exposure times.

Testing was conducted in an 8.1 × 6.8 m (26.6 × 22.3 ft) simulated OR with a 3 m (9.8 ft) ceiling height. Six Visium 1 devices with Clear Optics were installed at a height of 2.8 m (9.2 ft) above the floor. A modification of the American Society for Testing and Materials (ASTM) standard quantitative disk carrier test method (ASTM E 2197-02) was used. ⁸ The test organism was a clinical MRSA strain; MRSA was chosen for testing given reports that it may be transmitted in the anesthesia workspace. ^{Reference Munoz-Price, Bowdle and Johnston3,Reference Loftus, Brindeiro, Loftus, Brown, Charnin and Dexter4} A 10 µl inoculum containing 10⁴–10⁵ colony-forming units (CFU) of MRSA was spread to cover 20 mm steel disks with 5% fetal calf serum as a soil load. The inoculated disks were placed at 10 sites in the room within 3.05 m (10 ft) of the nearest lamp, including horizontal, vertical, and partially shaded sites. The disk locations included the OR patient tabletop (horizontal), patient table side (vertical), patient table bottom (partially shaded), floor beside patient table, adjustable light top, adjustable light bottom (partially shaded), sterile item table top, sterile item table side (vertical), floor beside sterile item table, and workstation in the corner of the room. Far-UV-C irradiance was measured using a radiometer (UIT2400 Handheld Light Meter for 222 nm (Ushio America, Cypress, CA). Testing was completed with exposure times of 4 and 16 hours. The supplementary material provides a picture of the simulated OR with the locations of the far-UV-C devices and the test sites.

Figure 1 shows reductions in MRSA and irradiance readings in the simulated OR with 6 Clear Optics devices. After 4 hours of exposure, MRSA was reduced by ≥2 log₁₀ CFU at 5 of 10 sites. After 16 hours of exposure, MRSA was reduced by ≥3 log₁₀ CFU at 6 of 10 sites and by ≥2 log₁₀ CFU at 8 of 10 sites. The sites with the lowest levels of reduction had low irradiance readings and were partially shaded (ie, bottom of the patient table and bottom of an adjustable light) or in the corner of the room outside the area of maximal light exposure.

Figure 1.

Reduction in methicillin-resistant Staphylococcus aureus (MRSA) on steel disk carriers in a simulated operating room after 4 and 16 hours of exposure to far-ultraviolet-C (UV-C) light delivered by 6 ceiling-mounted Clear Optics devices. White diamonds indicate irradiance measured at each test site with a radiometer. Error bars show standard error. Log₁₀ reductions were calculated in comparison to untreated controls.

In summary, we demonstrated that a ceiling-mounted far-UV-C technology reduced MRSA contamination at multiple sites in a simulated OR. After 4 or 16 hours of exposure, MRSA was reduced by >2 log₁₀ or >3 log₁₀ at 50% or more of the test sites. Although light delivery was reduced in partially shaded areas, average reductions of 1.8 to 2.3 log₁₀ CFU of MRSA were achieved after 16 hours of exposure. Given that multiple studies have demonstrated suboptimal cleaning and disinfection in ORs, ^{2,Reference Munoz-Price, Bowdle and Johnston3,Reference Xie, Sax and Daodu5} our results suggest that the far-UV-C technology could be useful as an adjunctive measure. The potential advantages of the far-UV-C technology over standard UV-C room decontamination devices include minimal personnel time requirement after installation and continuous decontamination during procedures.

Our study has some limitations. Testing was conducted in a simulated OR with inoculated steel disk carriers in a limited number of sites. Additional testing is needed to assess efficacy for real-world surfaces in ORs. However, previous studies have demonstrated that far-UV-C light is effective in reducing contamination on a variety of surfaces including portable equipment. ^{Reference Memic, Torres-Teran, Cadnum and Donskey7,Reference Huang, Yang and Hsiao9} We did not assess ozone production. However, we have previously demonstrated that no ozone accumulates in well-ventilated (ie, 8 air changes per hour) hospital rooms with 6 Ushio Care 222 devices operating. ^{Reference Memic, Kaple, Cadnum and Donskey10}