24 December 2020
Key Considerations for Engineering Design in US Hospitals
Hospital patients are one of society’s most vulnerable groups, which makes it imperative that healthcare facilities make them comfortable and safe for the duration of their stay. As the cost of healthcare and hospital stay in the United States is considerably more expensive than most other Western countries, patients and healthcare workers are entitled to high-quality engineering design or MEP (mechanical, electrical, plumbing) design in a hospital. Engineering design services must ensure the continuous operation of hospital facilities at all times and in all areas.
It has been reported that in 2019, approximately $11,000 was spent on healthcare per person in the United States. Research has also uncovered that though there are shorter hospital stays, more knee replacement surgeries and fewer angioplasties, the costs for these procedures are more than in other countries. For the prices they pay, patients in the US must expect building services design consultants to both fulfil codes and guidelines and prepare for all eventualities in hospital design.
Building services design consultants or HVAC engineers must consider:
- Codes and guidelines
- Equipment coordination
- Occupant comfort
- Chemical, physical and biological contaminants
When planning or designing a hospital in the US, there are various steps to consider. Engineering design professionals must:
- Understand the space and specific user needs
- Determine the activities and procedures that may take place in each space and any unique temperature (other than 68-75ºF in operating rooms and pharmacies) or humidity requirements (higher for burn units)
- Select medical equipment for each space
- Compare pressurisation, air change and exhaust requirements of rooms and sections to actual heating and cooling loads, including the envelope, lights, people, specialty equipment, refrigerators, sterilisers and major imaging equipment.
- Ensure uninterrupted power supply at all times
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provides guidelines for patient care areas in new hospitals, modifications to existing hospitals and any additions. Some of these guidelines concern:
- Air changes per hour
- Filtration and air distribution requirements
- Pressure relationship requirements
- Humidity and temperature requirements
- Correct air distribution devices and diffuser arrays must be used for each space.
- Diffusers must be correctly placed in patient and operating rooms.
- Non-aspirating Group E diffusers must cover 70% of the area over a surgical table and 1 foot out from the table to create a sterile field.
- Air must flow evenly over patients and doctors and the movement of room air must be minimum across the sterile field.
- Anaesthetic gases can be pulled out of the operating room with low-wall returns 6 inches above the finished floor.
- Terminal boxes and humidifiers must ideally be positioned in corridors. If not, piping must be panned with drainage.
- Air needs to flow from clean to dirty areas of a hospital.
- Operating rooms, delivery rooms, airborne infection isolation rooms, protective environment rooms and central sterile departments should have pressure-monitoring devices.
- Inpatient care facilities, recovery, critical and intermediate care areas and burn units must be fully ducted.
- Combination airborne infection isolation rooms, protective environment rooms, operating rooms, compounding pharmacies and central sterile department suites need pressure-monitoring devices with alarms.
- Pressure-sensitive areas must be fully ducted.
- MEP consultants may need to factor in extra ceiling plenums or interstitial space to accommodate the required ductwork.
Several hospital areas need air to be removed to the outdoors by an exhaust device. Some of the air that is removed by an exhaust can be toxic and is required to be discharged 10 feet above the roof of the topmost floor. Some of these areas are:
- Airborne infection isolation rooms (need dedicated exhaust system)
- Bronchoscopy and sputum collection and pentamidine administration rooms (must be at least 25 ft from outdoor air intakes and far from open windows)
- Emergency department public waiting areas
- Nuclear medicine hot labs
- Radiology waiting rooms for patients waiting for chest x-rays in case of respiratory disease
- Hazardous drug-exhausted enclosures
- Laboratory work areas with chemical fume hoods (must discharge at 2,500 ft per minute)
Valves that track exhaust air are used to maintain room pressure differentials and correct exhaust levels.
Bacteria and virus growth are encouraged with humidity levels that are too high or too low. If the humidity level is too low, it can cause premature coagulation during surgery or increased static on imaging machines. This can affect image clarity and can even damage equipment. These are some of the steps that can be taken to maintain the right humidity levels:
- Set winter humidity levels at 30% and summer humidity levels to a maximum of 60%
- In burn units, higher humidity can provide greater comfort for burn victims, help the healing process and reduce scarring.
- Humidification is provided at the unit level or in ductwork, which should be less than 90% and should have a duct sensor near the injection source.
- ASHRAE will allow adiabatic, high-pressure water-atomising humidifiers, provided that reverse osmosis water is used with ultraviolet sterilisation and a submicron filter.
In addition to these considerations, there are some considerations specific to hospitals that are outside the guidelines of ASHRAE. One of them is regarding the selection of the right hospital equipment.
Ventilation and pressure requirements must be met continuously, so most HVAC equipment placed in hospitals and entire rooms will be on emergency power, such as:
- Exhaust fans
- Chilled water pumps and chillers
- Heating equipment
- Airborne infection isolation rooms
- Protective environment rooms
- Supply and return fans
Spare systems must be in place for equipment used for cooling that is heavier than 400 tons. For heating, in case of failure or maintenance of the main system, extra equipment must be available for:
- Emergency procedures
- Labour and delivery functions
- Inpatient care rooms
Also, as airborne bacteria can cause hospital-acquired infections (HAI), air filtration systems are mandatory. These filtration systems are typically placed in the ceilings of operating rooms, pharmacies and protective environment rooms, taking into account the static pressure drop of dirty filters. Filters also need to be replaced based on any drop in pressure.
Before MEP design can begin, it is essential to access the information on an MRI room site-specific layout from the manufacturer. Data provided in these documents include the equipment’s heat load, requirements for chilled water supply, range of humidity levels, quench vent requirements, oxygen deprivation sensors and emergency exhaust fan placement.
Additional considerations for hospital engineering design include the following:
- Certain room equipment in rooms may need special ventilation for the additional heat generated.
- There may be containment hoods that are connected to exhaust systems by ducts, and some workstations may need a specific kind of compressed gas, vacuum or filtered water.
- It is necessary to assess special requirements for site-specific equipment cut sheets, provided by the medical equipment vendor.
- The hospital facilities must have uninterrupted electricity supply.
- Internal air quality must be high to improve patient health.
As discussed above, there are many layers of considerations for engineering design services in a US hospital. A vast amount of detail is required, and this is where the Building Information Modelling (BIM) process becomes useful, as it organises, modifies, updates and calculates significant amounts of data quickly and accurately. With the right BIM MEP services provider on board, possibly experienced and well-qualified MEP designers in India, all the considerations of mechanical engineering design services can be covered precisely, cost effectively and on time to ensure safe and continuous patient care in US hospitals.
XS CAD has valuable experience providing BIM MEP services, engineering design services, building services coordination and M&E design engineering support for global firms. Our range of mechanical engineering design services for MEP consultants include MEP drafting, MEP BIM modelling and MEP coordination.