Cabrini Medical Center

Ultraviolet = ultra-efficient disinfection

Cabrini Medical Center's new UVGI system helps protect the patients and employees from transmission of infectious diseases such as tuberculosis. A primary concern was the Stuyvesant Polyclinic, a designated AIDS center that provides its outpatient HIV services. Some of the clinic's patients are immunocompromised and at increased risk for TB infection.When they recently saw a sharp rise in the incidence of tuberculosis (TB) in a segment of its patient population, it enacted additional preventive measures. The solution was a low-cost, quiet and energy-efficient system.

The Challenge	Cabrini Medical Center (CMC) in Manhattan recently saw a sharp rise in the incidence of tuberculosis (TB) in a segment of its patient population
The Traditional Approaches	The clinic relied on the waiting room's high ceilings, HVAC (heating, ventilation, and air conditioning) system, and ceiling fans to help circulate and remove airborne droplet nuclei.
The UVGI Solution	Two nine-watt mercury vapor lamps in each unit produce UV-C radiation with a 253.7 nanometer (nm) wavelength. When a microorganism in an airborne droplet nuclei passes through this irradiation, its DNA is penetrated and destroyed, disabling the microorganism's ability to replicate and transmit disease.
The Results	The new UVGI system provides improved protection against TB and other infectious diseases.
What did it all cost?	The four UVGI fixtures cost $2500, and required two days for installation.

The Challenge: Protecting Patients and Staff from Airborne Pathogens

When Cabrini Medical Center (CMC) in Manhattan recently saw a sharp rise in the incidence of tuberculosis (TB) in a segment of its patient population, it enacted additional preventive measures. A primary concern was the Stuyvesant Polyclinic. CMC is a New York designated AIDS center, and the clinic provides its outpatient HIV services. Therefore, some of the clinic's patients are immunocompromised and at increased risk for TB infection.

Each patient who came into Stuyvesant Polyclinic's waiting room registered and then waited to see a doctor. As many as 50 patients were in the 40-foot by 40-foot room at one time. Patients expel small "droplet nuclei" when they cough, sneeze, or even talk. If droplet nuclei containing disease-causing organisms are inhaled and deposited, in the lungs or respiratory tract of employees or other patients, the organisms can spread infectious diseases such as tuberculosis (TB), measles, and influenza.

To combat this problem, CMC first changed the way patients were processed when entering the clinic's waiting room so that patients likely to be TB carriers were isolated. Now when patients enter the Stuyvesant Polyclinic, staff members immediately evaluate them according to updated TB correlation data. Suspected TB patients are isolated or removed from the general waiting room population.

The medical center also considered available engineering options that would further ensure the safety of waiting room patients and staff. It decided that Ultraviolet Germicidal Irradiation (UVGI) offered the best and most cost-effective supplemental protection against airborne pathogens.

The Traditional Approaches

Stuyvesant Polyclinic was built in the 1800s. The clinic relied on the waiting room's high ceilings, HVAC (heating, ventilation, and air conditioning) system, and ceiling fans to help circulate and remove airborne droplet nuclei. To increase protection, CMC considered adding combination ultraviolet (UV) high efficiency particulate air (HEPA) filters to the waiting room. But UV/HEPA units that already cleaned the air in other hospital areas took up valuable floor space and generated annoying noise. In addition, workers had to replace pre-filers monthly and service motors and blowers regularly. So equipment replacement costs and maintenance labor costs were high. Personnel replace HEPA filters and UV lamps less frequently, but HEPA filters were costly,

Upgrading the clinic's HVAC system to provide additional air cleansing would have been prohibitively expensive and would have created excessive noise and drafts. Another option, creating negative pressure in the clinic's waiting room, would have been ineffective in such an open area.

The UVGI Solution

When CMC received Ryan White Title 1 funds, it was able to install UVGI systems to reduce the chance of airborne disease transmission. In August 1995, CMC installed four electric UVGI fixtures at nine-foot heights in the corners of the clinics waiting room. Two nine-watt mercury vapor lamps in each unit produce UV-C radiation with a 253.7 nanometer (nm) wavelength. When a microorganism in an airborne droplet nuclei passes through this irradiation, its DNA is penetrated and destroyed, disabling the microorganism's ability to replicate and transmit disease.

Louvers in each fixture serve to:

Direct the UVGI beam into an intensely irradiated upper room zone to kill pathogens there.
Minimize UV-C intensities at eye level (since the eye is the body part most sensitive to UV-C radiation).

To avoid direct UV exposure, workers turn off the fixtures when dusting, inspecting and changing UV lamps, or during any other upper room work.

Air in the lower regions of the room must be circulated to the upper region where the air will be exposed to the UV-C energy and disinfected. The required circulation can be provided by ceiling fans or other air circulation systems. Ceiling fans ensure adequate vertical air flow and mixing.

The Results: Quiet, Effective Air Disinfection

Cabrini Medical Center's new UVGI system provides improved protection against TB and other infectious diseases and offers many additional benefits.

Highly effective protection from airborne pathogens. Studies indicate that, given sufficient UV intensity and exposure time, the 253.7 nanometer UV-C radiation produced by UVGI units destroys virtually all organisms carried in airborne droplets.
No noise. The UVGI units are absolutely silent, so patients are not distracted by the humming noise produced by some UV/HEPA units.
Improved appearance. The stainless steel UVGI units are architecturally styled, attractive, and unobtrusive.
No footprint. The wall-mounted units free up floor space for patient separation, comfort and safety.
Easy maintenance. Units require monthly cleaning and dusting by hospital personnel.
Minimal maintenance costs. The UVGI units have no mechanical parts to maintain and repair. Total yearly labor cost for all of the UVGI fixtures is estimated at $480.
Safe operation. The UV-C lamps are totally enclosed to reduce any possibility of tissue irritation that might be caused by direct exposure. Units are mounted at 9-foot heights to reduce exposure at eye level. The National Institute for Occupational Safety and Health has established that germicidal UV exposure levels less than 0.2 microwatts per centimeter over eight hours causes no eye irritation.
Low capital cost. The UVGI fixtures cost $2500 for all four units. Estimates to upgrade the HVAC to produce equivalent air cleansing were over $100,000.
Low operating costs. Yearly electrical operating cost for all four UVGI units averages about $40, compared with $3,600 for an upgraded HVAC system

What did it all cost?

The four UVGI fixtures cost $2500, and required two days for installation. Each UV lamp in the UVGI fixtures has an 8,000 hour life and is replaced annually at a cost of $16. By comparison, HEPA filters used elsewhere in the facility are replaced every two years at a cost of $200 each.