Ambulatory Surgery Center a model of infection management and contamination control
With increased outside air, special exhaust systems, positive/negative pressure rooms, direct digital temperature controls, and air filtration systems, the retrofitted facility now offers the latest in high-tech medical environments.
By Susan English-Seaton
In January of this year, Beth Israel Medical Center, located in New York City`s busy Union Square, opened its new ambulatory surgical center, a prototype urban retrofit offering not only the latest in high-tech medical and environmental systems, but a radical new design concept based on creating a more patient-friendly environment.
The conversion of existing fourth floor office space in Beth Israel`s five-story Phillips Ambulatory Care Center into a full-service, state-of-the-art ambulatory surgery center posed many engineering challenges to the project`s architectural team — Larsen Shein Ginsberg LLP and Cosentini Associates LLP. It involved increasing outside air, special exhaust systems, positive/negative pressure rooms, direct digital temperature controls, and air filtration systems to service the center`s operating and recovery rooms, as well as support areas.
A new concept in design
Drawing patients to ambulatory care facilities has become a pivotal strategy for health care providers in the competitive, market-driven health care environment. To keep pace, new facilities have changed their design dramatically to reflect a philosophy of patient-centered care. In urban centers, these facilities are usually retrofits. According to Angela Claudatos Parks, an architect with Cosentini Associates, clinics being opened as retrofits represent “a big movement now in hospitals. In New York City, there are a lot of hospitals doing this. They`re going into already-existing buildings, assessing their infrastructure, and then retrofitting the spaces to make them ambulatory care facilities. They`re trying to change the image of people having to come in for health care, trying to make it more patient friendly, and the whole environment a happier one with a less sterile look about it. So our MEP systems had to reflect that in the sense that they had to be very flexible and very accommodating to different temperature ranges.”
The new design departs dramatically from the traditional. It is based on a sterile core, which serves as the medical/surgical hub of the suites — completely isolated from the patient area. Flexible operating rooms are designed to be generic and equipped to accommodate a wide variety of procedures, rather than specific types of surgery. This inner core houses scrub sinks for surgeons, an instrument sterilization area (all instruments are sterilized in-house), sterile instrument storage, and warming cabinets. Stainless steel walls and hard surface floors are designed to ensure cleanliness; to enhance flexibility, all storage is portable. The floor plan respects the privacy of patients, allowing them to leave their private dressing rooms and emerge directly onto a patient-only corridor circling the suite of six operating rooms (ORs). Patients enter the OR through a door off this corridor; physicians enter separately from a second door off the core clinical area. Each OR is 400 square feet — large by urban standards. When combined, the six operating rooms can accommodate up to 7,000 outpatient surgeries per year.
Of the challenge of providing updated air-handling for the 75,000 sq. ft. space, Cosentini`s Parks says, “Beth Israel asked us to perform a feasibility study on the floors to see if a retrofit was possible. We had to work closely with Larsen to make sure enough space for return fans and filters was added. Filtration on the supply side was necessary, but we needed to have the space to properly install it, access it, and make sure the airflow wasn`t restricted — also, the additional return air — to make sure we were getting the air back to the systems properly. Additional fans for outside air were necessary to increase the outside air percentage.” The system is capable of operating on 100 percent outside air on an airside economizer, says Parks, but the air is returned. Condenser water capacity had to be assessed, and fans were changed to variable frequency drives so that a VAV (variable air volume) system vs. a constant volume system could be offered in areas where needed.
The existing air-handling units of the base building system had to be completely refurbished with HEPA filters, variable frequency drives, and return fans to supply filtered air and to maintain adequate airflow to patient care areas. New outside air fans were installed to provide additional outside air requirements. In addition, exhaust air was filtered with HEPA and/or carbon filters to meet code requirements and also to minimize odors for adjacent occupants.
To accommodate the special environmental requirements of the OR suite, a new 45-ton air-handling unit generating approximately 15,000 cfm was installed to provide dedicated service to the OR suite, including recovery and associated sterilizing areas. Housed in its own specially built mechanical equipment room, the system includes 90 to 95 percent high efficiency final filters, a humidifier, variable frequency drives, and a return air fan. In addition, each of the six ORs was provided with reheat coils and humidifiers, so that temperature and humidity within each OR could be individually controlled. Not only was air supplied `high` and exhausted `low` off the floor so anesthesia and other medical gases could be passed, says Parks, but because of the proximity of four residential towers above the ambulatory center complex, all exhaust had to be filtered.
In the OR, a constant air change rate of 2.5 air changes per hour is mandated, and a temperature range of 70 to 75 degrees Fahrenheit and an rH of 50 to 60 percent maintained in all operating spaces. Air is distributed at low velocities via laminar flow diffusers and exhausted through floor-level registers. Laminar flow diffusers are vital because of their capacity to generate a continuous, sterile field of low-velocity HEPA-filtered airflow at high volume around each operating table, which protects the patient, the surgeon, the assistant, and the anesthesiologist from both drafts and contamination.
“The laminar flow diffusers provide an isolated field around each table. They are usually ranged in a somewhat rectangular or square pattern, with the patient inside the rectangle,” says James Snyder, Larsen Shein Ginsberg`s architect on the project. “Air comes down in a curtain surrounding the table and is pulled out to the side through two separate returns, each in opposite corners, so that you`re constantly getting a supply of fresh, HEPA-filtered air over the patient.”
A manifold medical gas system with distribution piping was installed to service the surgical suite. Gas columns dispensing medical gases are laid out on a diagonal and include oxygen vacuum, anesthesia scavenging, nitrous oxide, nitrogen, and medical air. Laser and portable x-ray power outlets serve each room. Gas is distributed to the various outlets in each OR — isolation valves for emergency shutdown. All electrical systems were upgraded and, to ensure continuous uninterrupted operation, an emergency generator was installed to supply emergency power to the entire Beth Israel complex.
Negative and positive pressure rooms
Pressurization is controlled by a complete, standalone DDC-based (direct digital control) computer airflow control system. Remote control panels adjacent to the rooms include position switches (positive or negative), mode and alarm indicators and digital display of pressurization, airflow, and alarm conditions.
In the complex`s isolation rooms (holding areas for pre-op or post-op patients), either positive or negative pressurization may be required, depending on the need to isolate patients who are either infectious or who can be easily infected. According to Parks, the solution was a control system that could adjust a room to whatever pressure was required via a switch on a panel located right next to the room. “Generally in ambulatory surgery, you don`t operate on very sick people. Sometimes you will find that patients have TB, and therefore, you need to be in a negative environment. If their immune system is compromised, you want to have the room pressurized so they won`t be susceptible to infection.”
Rooms where soiled instruments are kept — so-called `dirty` rooms — are generally kept at negative pressure. In the instrument processing area, instruments are washed by hand, put into an ultrasonic cleaner, and then into a washer/decontamination unit. These decontamination units have both a dirty and a clean side separated by a stainless steel wall, with a door leading to the clean side. Instruments are taken out and put into packs for the various procedures, and then autoclaved.
In the support areas, flexibility was achieved by using a “wet wall” system, in which plumbing risers were located inside walls separating each suite. This allows for the relocation of plumbing fixtures as required by users without going to the floor below. Self-contained variable volume diffusers were installed to provide individual room control and to permit relocation of diffusers as needed.
In the OR, wainscoting was finished in a solid surface material typical of that used in kitchen cabinets. According to Snyder, it is impervious to just about everything, including bumps and/or microbial growths, and can be cleaned very rigorously, and there are no flat, exposed edges. The material — DuPont`s Corian — comes in 30-inch-wide sheets, which can be welded in twos. The application of a chemical bonding liquid turns two sheets into one 60-inch solid sheet, virtually eliminating joints. Wainscoting is terminated about 42 inches above the floor and covered by a rounded rubber bumper, also capable of being cleaned with disinfectants and vigorously scrubbed.
Floors are sheet vinyl and chemically bonded to form a seamless floor. There are no 90-degree corners. Intersections of walls and floors feature coved bases, rounded and extended up the wall approximately 8 inches, and capped off with a stainless steel top for easy cleanability. CR
Atrium view: Besides high-tech equipment and services, a convenient location, and a clean, infection-free environment, the new facility uses natural sunlight, which bathes the entrance — a two-story, skylit atrium filled with trees and an indoor waterfall — a view which can be enjoyed by those sitting in the family waiting area. The waiting area itself is located on an open internal terrace and is visible from the patient waiting area through a wall of windows, providing a comforting point of contact between patients and their families.
In the instrument processing area, instruments are washed by hand, put into an ultrasonic cleaner, then into a washer/decontamination unit. When taken out of the decontamination unit, they are put into packs for the various procedures and then autoclaved.
Part of the core area of the Ambulatory Surgery Center used for flash-sterilizing and storage.
In the ambulatory surgery sterilization area, decontamination units have both a `dirty` and a `clean` side, separated by a stainless steel wall, with a door leading to the clean side.