Up and walking

Functionality *****
ACAD is an innovative walk-through day hospital that makes a clean break with the labyrinthine layouts of most long-stay hospitals, with their contorted internal corridors and mind-numbing barrages of signs. At ACAD, the patient flow through the building is as direct as in a factory production line and as clearly laid out as in a shopping mall. The facility is currently working at only 60% efficiency because of management difficulties in scheduling doctors' appointments. The building has also proved to be adaptable to constantly changing needs.

Impact *****
Patients are welcomed by a daylight-flooded interior that one would more commonly expect to find in a smart hotel than a hospital. Internal and external materials and furniture are all high quality though not luxurious.

Build quality ****
Robust materials and an efficient environmental control system, with a clear division between high and low serviced areas, make the building easy to maintain and adapt.

(Evaluation criteria of the Construction Industry Confederation's design quality indicator have been adopted by the Building Revisit series.)

At a glance

ACAD is one of Britain's most seminal healthcare buildings in a decade. Completed as part of Central Middlesex Hospital in north-west London in June 1999, ACAD stands for Ambulatory Care and Diagnostic Centre, which in layman's terms means a walk-through day hospital. It is an innovative healthcare building type in which non-emergency operations can be efficiently programmed in a manner similar to a factory production line. The building has also been acclaimed as a model for high-quality public architecture and was even chosen for the cover of Tony Blair's architectural manifesto Better Public Buildings of October 2000.

The North-West London Hospitals NHS Trust commissioned the design from Avanti Architects, with Arup as structural and services engineers and James Nisbet & Partners as quantity surveyor. The 8100 m2 building was built by John Laing Construction for £19m, including fees, equipment and furniture.

Functionality

Good patient flow
"The building works very well," says ACAD's clinical director, Dr Giordano Abbondati. "The basic principles behind it work, and the flow of patients is very good." And if that wasn't enough, estates manager Dave Butland enthusiastically asserts that "this building is a rip-roaring success".

ACAD was originally devised as a result of what Abbondati calls "process re-engineering or hospital deconstruction". The big idea was that all "elective" or non-emergency operations, such as cataract removals, hip replacements and dental surgery, should be carried out in a new stand-alone centre, thereby reducing the waiting list at the acute general hospital next door. Operations can be carried out relatively quickly using keyhole surgery and local anaesthetics, from which patients recover in a matter of hours rather than days. With no emergencies to disrupt the flow, diagnoses and operations can, in theory, be efficiently programmed in advance.

The two-storey building layout was designed around this linear production line. It is in essence a walk-though hospital: patients walk in at one end, and without retracing their steps, emerge from the other end a few hours later with their hernias or cataracts treated. A central mall divides a low-tech wing on one side, containing consulting rooms and patient recovery areas, and a high-tech wing on the other side containing all the highly serviced radiodiagnostic rooms (including advanced MRI and CT scanners), endoscopy rooms and operating theatres. The patient checks in at the reception desk, walks down the central mall and up a prominent open staircase to the consulting rooms. After pre-assessment, the patient is walks across a bridge over the mall to an operating theatre, and after the operation is wheeled back over the mall to a recovery area. After a few hours they are discharged through the back door.

Feedback from questionnaires reveals a high level of patient satisfaction. The questionnaires have a response rate of about 30% of patients, of which as many as 80% are satisfied with the facility, and 82% with the level of care.

Poor resource management
Sadly, Abbondati has to admit that, three years after opening, the day hospital is only functioning at little more than 60% efficiency, with two of the six operating theatres working "at half blast". The current annual throughput amounts to some 17,500 cases of diagnosis, endoscopy and operation.

The reason for the under-achievement is that ACAD's management has not yet cracked the scheduling of operations, much of which lies beyond its control.

The efficient production-line system relies on each operating theatre being assigned to one surgeon for a half day at a time, so that an uninterrupted sequence of similar operations can be carried out in quick succession. This system works well in the USA, where the day hospital concept was pioneered. But in ACAD's catchment area of north-west London, GPs refer patients to the specialist consultants of their choice, not all of whom are attached to ACAD. This results in an uneven workflow and inefficient use of ACAD's medical resources.

However, Abbondati is optimistic that throughput could nearly double over the coming year. A new overnight recovery suite has been fitted out, and this expands ACAD's scope from day surgery to short-stay surgery. More invasive surgery such as tonsil removal and gall bladder treatment, which call for recovery periods of up to 18 hours, can now be carried out. The overnight recovery suite has also paved the way for ACAD's working day to be extended to 8.30pm to fit in more cases.

Another initiative to make fuller use of ACAD's resources comes from the local NHS strategic authority. It proposes that ACAD's catchment area should be expanded to cover most of greater London.

Waiting room bottleneck
The only bottleneck in the entire production line, according to Abbondati, is one of the three small pre-operation waiting rooms, where the 25 patients to be treated each day are required to check in at 7.30am and then sit in their gowns for much of the day. "We know from patient surveys that waiting before an operation is the least satisfactory part of the service," he admits.

Here again, Abbondati blames consultants being unwilling to adapt traditional procedures. "We wanted to avoid this situation by staggering appointments throughout the day. But traditional surgeons want to see all their patients at the start of day. They're used to the luxury of a general hospital, where patients are all lined up in bed the night before."

Clear intelligible layout
A distinct advantage of the building's simple, clearly expressed layout is that patients find their way easily and with the minimum of signage, an important consideration in an area where many patients do not speak English. After checking into the main reception desk, patients simply walk down the mall in front of them and take one of three staircases up to their appointed waiting room (indicated by a single digit).

Adaptable building
Many of ACAD's services have been changed since the building opened in response to the rapidly changing nature of medical practice. The building has undergone three major internal reconfigurations, and an even larger project for a 1600 m2 rear extension is out to tender.

The building was handed over with part of the first floor low-tech wing left incomplete and earmarked as research laboratories. These plans were abandoned and the space was converted in two stages to provide 19 overnight recovery beds.

In the high-tech wing, one of the five original operating theatres was split into two smaller eye surgery units for cataract operations. Two laser diagnostic rooms were converted to a dental suite serviced with general anaesthetics, but this practice has since dropped out of favour, and the space is soon to be converted again as a lithotripsy suite to treat gall bladder and kidney stones.

Butland claims that these changes were made possible by the building's flexible construction system. This was quite conventional and inexpensive, consisting of an insitu concrete frame with internal walls in dense concrete blockwork with plastered finishes. Metal stud walls would have been easier to replace, but were not sturdy enough to hang heavy medical equipment on.

The largest reconfiguration project was the conversion of the operating theatre on the first floor. Here, aluminium cladding panels were carefully removed and the inner blockwork leaf was knocked down to provide access for builders. Building works were sealed behind polythene sheeting to allow the centre to continue operating alongside. After completion, the blockwork inner leaf was rebuilt and the original cladding panels were carefully reinstated, leaving virtually no traces of the rebuilding.

In terms of smaller scale adaptations, the most work has involved installing additional circuits of structured wiring. Where corridors have had suspended ceilings this presented little problem, but several link areas in the building were designed with plaster ceilings, and these had to be cut out and reinstated.

However, Avanti director Claudia Bloom, argues that flexibility would be improved if the building's clinical facilities were rationalised into just eight standard loose-fit room types. "If the rooms were just 4 m2 larger in area, then you would be able to change the service without needing structural building work. The trouble is that funding is never generous enough."

Impact

Patient-friendly architecture
The week before Building's revisit, ACAD had been filmed to appear in a television drama – as a smart bank in Berlin. This illustrates not just the architectural distinction of the building, but also its radical break with the depressingly utilitarian conventions of post-war hospital architecture.

The highlight of the building is the wide, double-height central mall, with daylight flooding in through skylights, window walls and adjoining landscaped courtyards. "Visitors look all around in amazement," says Butland. "They say they shouldn't be here because it must be a private hospital."

Prime minister Tony Blair, who formally opened the building in 1999, recognised the welcoming, reassuring effect that such well-designed public areas have on patients, and that these should not be overlooked in the drive to make clinical facilities functional and convenient for medical staff.

Other attractive areas are the reception area, public cafeteria (let to Costa Coffee) and the recovery areas with views of the courtyards or landscaping. The furniture is as swish and inviting.

Harmonious adaptations
Telltale signs that the building has gone through extensive modifications since it opened three years ago are hard to find. This is largely because the NHS trust has had the sense to commission the modifications from the original architect, Avanti. In the case of the proposed extension, Avanti recommended that detailed design be passed on to another architect with a sympathetic design approach, Ansell & Bailey.

High-quality but inexpensive materials
Attractive and durable but inexpensive materials have been used internally and externally. Internally, blockwork walls are plastered and painted, and in the lift lobbies the paint finish is renewed every three months to keep them looking fresh.

Externally, the dominant material is fairface limestone blockwork, with a more luxurious patch of travertine limestone next to the main entrance. In an area of urban deprivation, the building has suffered from just one incident of graffiti. "If you treat people well with high-quality materials, then they will treat the building well," says Butland.

Build quality

Sound construction
Estates manager Butland says that the building suffered few latent defects. One was a defective aluminium flashing to a clerestorey window, which caused rainwater to leak into a patient recovery ward. It was patched up with mastic.

Efficient air-handling system
A complex air-handling system devised by Arup that provides full filtered air-conditioning to the high-tech treatment areas works efficiently and is easily controlled by a Honeywell electronic building management system, claims Butland.

Arup's fire strategy designated the central mall as a means of escape, with the stipulation that no combustible materials could be added to it. A welcome by-product of this policy is that the mall is left splendidly clear of all the noticeboards, posters and temporary exhibitions that too often silt up circulation areas in public buildings.

Energy efficiency
To reduce energy consumption, the low-tech wing was designed with a mixed-mode ventilation system combining comfort-cooled mechanical ventilation and opening windows. Paradoxically, Butland concedes that this actually increases running costs, as opening windows to ambient air adds to the heating or cooling load and increases cleaning bills.

Pigeon control
One unforeseen nuisance was that pigeons entered the mall through manually operated windows. Systems of wires and spikes fixed to external window sills and other perches proved ineffective, so the estates department resorted to covering both internal courtyards with inconspicuous netting at roof level, at a cost of £3000 each.