By Barry Hunt, Class 1 Inc., Canada
Recent events in the US healthcare industry have combined to create a rush by healthcare facilities toward the adoption of technology for total room disinfection. Events include: 1) changes to the Affordable Care Act that reduced CMS and insurer compensation to hospitals due to high rates of Healthcare Acquired Infections (HAIs); 2) elimination of CMS and insurer reimbursements to hospitals for individual patient healthcare costs if and when a patient develops an HAI; 3) a number of peer-reviewed publications of total room disinfection systems used at terminal discharge demonstrating successful reductions of either bioburden or HAIs or both; 4) presenter advocacy at recent infection prevention professional conferences including American Prevention and Infection Control (APIC) and Society of Healthcare Epidemiology of America (SHEA); 5) industry innovation; and 6) industry promotion.
In the ensuing market competition between hydrogen peroxide vapor (HPV) fogging and UV total room disinfection systems, UV appears to be the leader in the U.S., likely for reasons of speed, safety and ease of use19. Well-trained housekeeping staff can completely disinfect 20 to 50 patient rooms per day depending on the speed of the mobile UV system chosen. The faster the disinfection system, the faster the room turnaround, and the greater the improvement in hospital revenue; the less EVS staff time required, the lower the hospital operational costs; and there is no risk to staff or patients of exposure to residual aerosol disinfectant.
Of the two types of energy-based disinfection systems being marketed today, UVC has been a proven technology for disinfecting air, water and instruments for over a century2,3. UVC is a narrow spectrum technology operating at a frequency of 254 nm, very close to the optimal germicidal frequency (263 nm to 266 nm) for bacterial and viral disinfection.
PX light is a broad-spectrum technology developed in the 1950s primarily for flash photography. PX does however include some germicidal UV in its range of emitted light frequencies.
Efficiency
Narrow spectrum UVC emitters are relatively efficient at generating germicidal UV with a known range of efficiency from 24% to 38%. That means a bulb rated for 100 W input power from one manufacturer may emit 24 W of germicidal UV, while a 100 W bulb from another device manufacturer may produce as much as 38 W of germicidal radiation. Technologies known to impact this range include tubing materials, and temperature management. Further optimization of emission of UV energy onto surfaces can be accomplished with reflectance technology.
By contrast, PX bulbs are relatively inefficient at generating germicidal UV with a published efficiency of just 9%. Much of the input energy is wasted as heat and visible light, rather than being converted to germicidal UV. Consequently, for any given input power, a UVC lamp will emit approximately 4 times more germicidal UV than its PX counterpart.
Given the example of a typical US hospital receptacle that supplies up to 2000 watts of electrical power, the maximum germicidal UV output of a PX device can only be 180 Watts (9 % x 2000 watts = 180 watts), whereas a UVC device can generate 760 Watt of germicidal UV (38% x 2000 watts = 760 watts).
Disinfection efficiency is a direct function of the delivered germicidal UV power and exposure time. Therefore, it becomes quite clear that UVC can disinfect up to 4 times faster, or 4 times more, than a PX device from a single emitter using the same power (760 watts / 180 watts = 4.2X).
Efficacy
UVC constants have been published for all bacteria and viruses allowing easy calculation of time and power required for deactivation with germicidal UV. Disinfection constants vary greatly with the organism. In general, vegetative bacteria are deactivated very quickly, spores require a lot more time.