Multicentre audit of the efficiency of hospital-wide central vacuum systems

Abstract

Vacuum suction is a critical clinical tool used to maintain airway clearance; manage respiratory conditions; and facilitate drainage therapy and specialised wound care. Most hospitals provide wall-mounted suction ports connected to a central vacuum system. These systems include multiple pumps; backup units; and extensive pipework. While designed for reliability, they are prone to entrainment and leaks due to the high number of end ports, resulting in energy consumption even when suction is not used actively. Portable on-demand suction devices, powered by batteries or mains electricity or driven by compressed air or oxygen through a Venturi effect, offer an alternative that operates only when required and may reduce environmental impact and costs.

A prospective audit was conducted across three UK hospitals (Raigmore Hospital, Inverness; Aberdeen Royal Infirmary, Aberdeen and Sheffield Children's Hospital, Sheffield). The data collected focused on equipment usage, with no patient interaction and included the number of suction ports for each ward and the frequency and duration of suction use. Electrical consumption was inferred from logbooks and kW ratings of pumps. Carbon emissions were calculated using UK government greenhouse gas conversion factors [1].

Across all hospitals, high-acuity areas such as operating theatres, endoscopy and ICUs reported daily suction use. In contrast, low-acuity wards showed substantial underutilisation. For example, single episodes of suction use of < 30 s over the course of a month were reported in medical wards with ≤ 26 wall ports. Similar patterns were observed across the audited hospitals, indicating systemic overprovision of central vacuum system infrastructure (Table 1). Most suction procedures last < 3 min, with many lasting < 30 s. Usage for 3 min represents just 0.2% of a 24-h period, meaning the system remains clinically unused for 99.8% of the day while pumps maintain a continuous negative pressure.

Compressor logbooks at Raigmore Hospital revealed intermittent operation of 3 kW motors on a ‘duty cycle’ – sequentially running whenever the vacuum pressure falls to a lower limit. Even with minimal clinical demand, negative pressure must be maintained across the entire pipe network. Average weekly energy use was logged at 490.5 kWh, giving an annual total of 25,506 kWh which emits 4515 kg of carbon dioxide equivalent (CO₂e) and equates to 1300 tonnes of CO₂e emissions across the UK.

Annual financial costs for running the Raigmore Hospital central vacuum system pumps amount to £7396 ($9941, €8551) for electricity, not including maintenance. Based on 123,000 acute beds across the UK [2], the potential annual green dividend of reviewing central vacuum system provision is > £2.0 million ($2.69 million, €2.31 million). For new build hospitals, a current stage 4 tender for a 450-bed hospital lists the central vacuum installation at £1.47 million ($1.97 million, €1.70 million) [personal communication].

The findings reveal a fundamental inefficiency in hospital-wide central vacuum system deployment. Whilst deemed essential in high-acuity areas, central vacuum system infrastructure is vastly underutilised in general wards. The design of the system, with the need to maintain vacuum over and above any allowable loss, multiple cycling pumps, extensive pipework and unavoidable leaks, means that energy consumption is driven not by clinical need but by the requirement to maintain a negative vacuum pressure.

Portable on-demand suction devices offer a practical alternative with the environmental advantage of reduced energy consumption. They operate only when needed in general wards and for emergencies as mains and battery powered units (though require maintenance and a battery replacement programme). Venturi units have the advantage of very low maintenance requirements and at a cost-point similar to the existing vacuum control devices. The units are powered by compressed medical air or oxygen, and some allow simultaneous vacuum and oxygen delivery. However, because they are powered by compressed gas, the embedded carbon and financial cost must be considered when analysing leanest service options. For high-volume surgical use in operating theatres and endoscopy units, on-demand systems such as Stryker Neptune (Stryker UK, Newbury, UK) [3] or Drainstar (M.A.S. Medical s.r.l., Racconigi, Italy) [4] allow direct discharge to grey water systems, which improves staff wellbeing by reducing moving and handling requirements, and decreases clinical waste tonnage and transport of surgical fluid for high temperature incineration [5]. Though the recurring cost of filter procurement for this equipment is high, it should be compared with the capital and maintenance costs of hospital-wide central vacuum systems.

This work shows that centralised vacuum systems are environmentally and financially unsustainable in low-acuity hospital wards and could be replaced by on-demand units, with efficient alternatives also available for high-acuity areas. Despite suction being used for < 1% of the day in many areas, central vacuum system pumps must always maintain vacuum, generating substantial carbon emissions and financial costs. Transitioning to a hybrid model, or designing future hospitals without central vacuum systems, offers an opportunity to reduce carbon emissions, lower costs and maintain high standards of clinical care.