Pneumatic tube systems – the ‘invisible heroes’

Communication technologies like mobile phones and Wi-Fi have catapulted us into an era where today’s reality is often even more incredible than yesterday’s science fiction. However, when it comes to the transportation of physical objects, we are clearly a long way from replicating the type of teleportation machines synonymous with the Star Trek franchise.

So, how does a modern-day hospital cope with the accurate and timely transfer of thousands of critical supplies — such as blood samples, patient specimens, and pharmaceuticals — across its sprawling campus? The answer lies in a technology that can be traced back around 200 years. Pneumatic tube systems (PTS) exist in almost every major UK hospital, utilising the same combination of vacuum and air pressure that was first commercially used by the postal system in the mid-19th Century. Nowadays, a major NHS hospital PTS requires up to 5 kms of precision-extruded pneumatic tubing to transport sealed products throughout its network of floors, departments, and buildings.

Aerocom (UK), one of the UK’s largest suppliers and installers of pneumatic tube systems to healthcare organisations, has to date installed such systems in well over 100 NHS and private hospitals in the UK. The company’s most recent project involved the upgrade and replacement of the entire network of pneumatic tube systems across Bristol Royal Infirmary’s city centre hospital complex.

Pneumatic tube systems are piped networks that propel cylindrical carriers through arrays of tubes by low-pressure air movement or partial vacuum. Comparable to a national railway network, the mainlines are separated into both long distance and localised zones, with stations either inline, where the carrier passes through, or end of line branches. Each zone operates individually, the multiple zones of the network operate simultaneously and, like railways, there are interchange stations where the carrier can cross from one zone to another.

The physics is not entirely the same as the original postal systems used for transmitting telegrams on single tracks to nearby buildings such as Government offices or the Stock Exchange. The addition of 21st Century automation, computerisation, and robotic enhancements, mean the technology has developed from single lines to multiple station mainlines, with diversion branches and much improved traffic flow.

Making the networks largely invisible to users

While the design and installation task differs depending on whether the systems are being retrofitted, or designed for a new-build hospital, the goal is to make the tube networks largely invisible to hospital users. The pipelines may be installed through ceiling spaces or down service risers, for example, or buried underground if they are required to transport items between campus buildings. Central interchange hubs may be created within available service areas of the hospital.

However, while it may first appear to be a huge expense to install several kilometres of tubing in a hospital that may still need to remain fully operational while work is underway, the reality is entirely the opposite. In fact, tube systems save an enormous amount of time and staffing costs for the NHS. The modern PTS must be capable of dealing with several thousand specimens daily in major hospitals — and remember that is just specimens. A&E alone can account for up to 25% of the traffic flow of these largely unnoticed, but essential, hospital logistics services.

Reducing walking distances

The complex network of tubes vastly reduces what would previously have been the walking distance for hospital porters and medical staff delivering samples, or trips between the pharmacy and the patient wards or day units. This therefore makes the tube network a much more efficient process, and takes pressure off the hospital staff. The tube system also works ’24/7′, and never sleeps, eats, encounters security doors, uses lifts, has any distractions, time off, or holiday requirements.

Additionally, it has been calculated that it would take up to 30 extra porters in an average 1000-bed hospital to cover the same work as a site-wide PTS. The initial investment is recovered within several months of a system going into service, which is a huge saving for the taxpayer and the hospital Trust alike. Medical staff, likewise, have more time to focus on patient care and patient therapy.

A retrofit installation will typically take a few months per project. With a new-build hospital, the PTS designer may team up with the main contractor’s design engineers possibly six years ahead of the actual installation. Putting a project together is like constructing a 3-D jigsaw with thousands of components. Aerocom’s design team, headed by Graeme Bell, pre-plans and co-ordinates all systems, working with building architects and design engineers to also develop new systems for future hospitals.

Using the example of Bristol Royal Infirmary, which is operated by University Hospitals Bristol and Weston NHS Foundation Trust, the installed tube system includes 60 separate user group stations throughout the complex, mainly for the transportation of patient specimens. Another larger capacity network of seven stations transports drugs from the pharmacy to the wards or clinic areas. The whole thing must be seamless and 100% reliable.

Initially, hospitals utilised a basic point-to-point system. However, pneumatic tube systems were enhanced by developers in conjunction with developments in computer software. As a result, modern multi-zone systems are controlled by a central computer system, complete with RFID tracking and diagnostics. These systems will cope with multiple simultaneous and tracked transportations.

Station sizes and designs

Stations come in a range of sizes and designs. Standard design includes a loading port and an interface panel. With users keen to improve efficiency, the latest lab designs have features such as auto-unloading. Accessories can also be added to ensure safe and secure transport, including lockable receiving cabinets, or PIN code secured retrieval.

Diverters placed within the system are extremely important also, allowing packages to array to branch lines and/or change directions within the tube network. A diverter switches between sub-routes to guide carriers along the desired path. Once installed, diverters are operated automatically by the control system.

Another essential system component is the blower, which is the driving force behind pneumatic tube systems, providing the system with its air supply. ‘Blower’ is used to describe the single diaphragm exhausters that create the vacuum and air pressure within the transport tubes, causing the carriers (usually plastic canisters) to move. These exhausters create a difference in air density behind and in front of the canister. This difference in air pressure enables the carrier to be pushed or pulled along the tube. The blowers are calibrated for propelling containers through the system at speeds of up to 5 metres per second.

It is the computerisation rather than the physical properties behind the control of air movement that makes the modern pneumatic tube system so hi-tech.

Powerful dedicated software

Today, dedicated software can control and monitor an infinite number of ‘send and receive’ stations in unlimited zonal areas within a user-friendly Microsoft Windows package. Real-time graphics can display each carrier’s progress through multiple zone networks, using scanners to verify every RFID track-and-trace tag. As a result, every ‘transaction’ can be recorded, filed, and made accessible for future diagnostics, while added security functions can control access to the tube stations via PIN codes, swipe cards, barcode readers, and so on.

As with any technology these days, advances and improvements are being made continuously. Challenges surrounding the installation of pneumatic tube systems vary greatly from site to site. The system can be pre-designed into a new-build project far in advance, while a retrofit or upgrade project tends to be much more of a bespoke affair. For a retrofit or upgrade the surveyor will first review all departmental needs with the hospital — which may well have changed dramatically since any previous system was installed. Then, existing building plans and on-site visits will help determine the most efficient or cost-effective placement of tubes and tube stations, always looking to utilise available ceiling apertures and service areas. In simple terms it is akin to having a house rewired or replumbed, but on a much larger scale.

Last year, Aerocom (UK) was asked by St James’s University Hospital in Leeds to connect eight tubes leading from its Gledhow Wing to a new pathology laboratory (see HEJ — February 2024), with no existing corridors or service ducts. The tube system had to travel down an embankment and across a main road to a new service duct, requiring a trench to be dug to house the traversing tube system. Notwithstanding the inevitable obstructions that were uncovered, such as high voltage cables, the underground pipes must be leak and pressure tested before burial. The polyethylene high-density (PEHD) tubing is fusion welded, which is a more suitable plastic for buried pipes, and also needed to be transformed to adapt with the PVC tubes at either end of the connection.

Replacing an older system

The uncovering of ‘challenges’ can be very common when a new supplier is asked to upgrade or replace an older PTS that had been installed by another contractor. Royal London Hospital, for example, invited Aerocom in 2018 to review its 64-station PTS, which was installed by another contractor 10 years earlier. The system was suffering downtime, and the system software was regularly ‘freezing’. The site survey quickly discovered that the system controller was operating on Microsoft XP, which had been unsupported by Microsoft since 2008. The pneumatic operating system was also deemed to be too basic, with limited capacity to self-diagnose faults, and a myriad of other knock-on design and computer errors flagged.

As a result, the system was replaced in 2020. Only then did Aerocom installers discover the extent of poorly fitting tubing in the system — and ‘lost’ carriers dating back several months were discovered jammed in some of the worst sections. The newly installed system immediately reimbursed the Trust, allowing it to reduce the large number of porters that had been needed 24/7 to manually carry out the tasks that should have been performed by the tube system. In our calculations, the return on investment would have paid back within the first year, and will provide several millions of pounds in manpower cost savings for at least the next decade. 

So, until the unlikely day that patient specimens, drugs, and other items can be ‘beamed up’ Star Trek-style — instead of physically transported — the advances in pneumatic tube systems have led to them becoming one of the most indispensable sample handling innovations in modern hospitals.