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How can we better calculate evacuation times in hospitals and healthcare facilities? This article discusses the key issues, latest research, and technologies being developed to tackle this problem.
A complex problem
Planning the emergency evacuation of healthcare facilities is a challenging task. Hospitals often have expansive and complex building structures, while wards vary enormously in their design and function, with different layouts, equipment, patient profiles and staffing structures. There are likely to be large numbers of vulnerable occupants and people with reduced mobility (PRM) in occupation throughout a hospital – a far greater proportion than in other buildings.
Many patients will require continuous care before, during and after an evacuation. Being moved can be dangerous for critically ill patients, so evacuation procedures must also include triage processes with different strategies for different patient groups. Considering the destination and on-going support of evacuated occupants is crucial. These factors place additional importance on the methods of notification and emergency management to mitigate unwarranted risk during a false alarm or minor incident.
Clinical and public areas in healthcare facilities have highly variable occupancy levels, with patients presenting a variety of physical and mental capabilities. Many occupants routinely rely on aids, or on other people, for movement or visual/auditory assistance. In comparison to other building types, patients in hospitals are more likely to await personal staff instruction on hearing an alarm.
This means that the success of an evacuation relies greatly on the responses of staff members. But typically there is a high employee turnover in healthcare premises and therefore upkeep of training can be onerous. It is difficult to conduct frequent hands-on training as live drills are impractical, costly and arguably unethical.
Evacuating patients is particularly challenging when many require assistance and only a few members of staff are on hand (e.g. on a night shift). During an evacuation available staff must make many trips, assisting individual patients in turn. This is physically demanding, and the fatigue staff members experience may slow the process. Transferring patients between wards and through stairways can also cause blocking, and potentially delay the evacuation of others.
There are similar challenges in the evacuation of residential care homes, and mental health facilities. It can be expected that many people will require assistance to evacuate and therefore staff are similarly vital to the evacuation strategy. Given our aging population there will be even higher demand for care facilities in the future and therefore planning must consider more people with movement impairments than ever before.
Is horizontal evacuation enough?
To address this complex problem, healthcare facility management teams work to devise strategies for the safe evacuation of all hospital occupants in the event of fire. While fire and rescue services will play a key role during a fire event, the emphasis for evacuation planning is on in-house procedures. For example, to meet legal requirements in the UK, management must plan its emergency response assuming no evacuation assistance from the emergency services [1].
The most common strategy is progressive horizontal evacuation, where wards are allocated into compartments separated by fire resistant barriers. In the event of a fire, occupants are progressively moved into adjacent compartments away from the fire. This provides time to assess the situation, and to fight the fire. It is typically expected that horizontal evacuation will suffice, because of the fire protection installed between compartments, and that full hospital evacuation is unlikely to be required. But every year we see fire incidents in healthcare facilities and care homes where full building evacuation is needed, and many incidents that require some amount of vertical evacuation (via stairs) in addition to horizontal evacuation. Tragically, we also see more injuries and casualties from hospital and care home fires than from fires in other non-dwelling buildings where the population is likely to be more independent and capable of self-evacuation.
The perception that horizontal evacuation is likely to be sufficient has led to a lack of focus in risk assessments on the vertical component. In many guidance documents there are only cursory mentions of movement devices such as hospital ski skeets and evacuation chairs, or the sizing of stair refuges (e.g. to fit a single mattress) [2]. The lack of specific guidance about assisting patients in vertical evacuation adds to the perception that stair evacuation is not practicable or likely for vulnerable populations. This leaves gaps in planning and in the provision of training and equipment such as movement devices for evacuation down stairs.
Internationally, we now see taller hospital developments; for example, those with mid-rise bed towers and smaller footprints in urban areas. These changes, alongside diversity in the fitness and obesity levels amongst staff as well as patients, will impact both horizontal and vertical evacuation times.
Can we time this?
For an evacuation strategy based around protecting occupants through progressive horizontal evacuation, the importance of assessing the time required cannot be overstated. The success of a hospital evacuation in a developing fire situation is reliant on the time limits of fire protection and suppression measures available, alongside the timeliness of detection, notification, decision, and triage; and the cycle of patient preparation, movement, and reassessment.
Where a fire safety engineering approach is taken, a prediction of evacuation time must be made to estimate the “Required Safe Egress Time” and compare it to the tenability conditions, i.e. the “Available Safe Egress Time”. Similarly, in managing safety operations, risk assessments typically call for an estimate of evacuation time, typically accounted for in terms of distances and capacities (i.e. the travel distance from any ward, and the number of beds in that ward).
However, there is little guidance on methods to estimate evacuation time for hospitals. Broad approaches suggested include table-top exercises, hand calculations and the timing of other hospital evacuations [3]. Ideally, any calculation would be informed by drills in the building itself, but this is rarely possible and therefore is often substituted by “walk-throughs”. Applying walk-through times in traditional hand-calculation methods cannot capture the key factors: patient dependency, awareness and cooperation; the time taken to disconnect/reconnect medical devices and to prepare patients in movement devices; the time taken to travel the distance to an adjoining compartment in crowded conditions; and the numbers of staff members and their levels of training.
The use of movement devices is critical in assisting patients in evacuations. However, only wheelchair use has formal regulation; the stair devices such as ski-sheets and chairs which must be used in vertical evacuation are not regulated and their performance varies greatly, as does their appropriateness for different patient types. Guidance on the selection and use of track-type evacuation chairs is available [4], however performance factors of varying device types, such as their speed, are not yet considered. The use of such devices can affect the performance of other evacuees. Having devices in a flow of evacuating people can lead to blocking (due to physical or social factors) and changes in behaviours such as interpersonal distance. The time taken to prepare and use these devices, as well as their size, width and speed, is a crucial factor in the healthcare evacuation timeline.
In recent years these issues have been highlighted, particularly in the context of assisted evacuation for those with disabilities, prompting research and experiments to support these types of calculations. While much more is needed in addressing these crucial factors, two key improvements have been made: the provision of data and the development of assessment models. These improvements allow different designs and procedures to be quantified (albeit crudely) and then compared.
Data and models
While there are a wide range of commercially available devices that can be used to assist in evacuation in healthcare environments, there are only a few data-sets available to quantify their performance. The latest edition of the SFPE handbook [5] includes a summary of data available for quantifying assisted evacuation and movement of people with reduced mobility. We do not yet know enough about mixed-ability evacuation, but the experimental work to date provides a good starting point – particularly in showing the enormous variations in performance. For example, evacuation chairs used by expertly trained operators can achieve speeds (in experimental conditions) that are four times faster than those recorded in an evacuation drill where the operators were less well trained [6,7].
These data-sets on movement times for assisted evacuations can improve hand calculations, but only on a singular basis. It can help us to estimate the time for one assisted evacuee or for a number of evacuees as long as they are not moving simultaneously. We know that more space is needed in assisted evacuation: those who are assisting, plus the person being assisted, plus all of their medical and movement equipment (e.g. a wheelchair and a drip), will move in the evacuation flow together forming a larger footprint. An equation alone will not be able to properly represent the space taken by a range of movement devices alongside other evacuees; indeed typical flow calculations already make broad assumptions about the “average body size”, and are often based on out-dated flow data.
To address this, efforts have been made to add assisted movement to computational evacuation models. This provides a way to capture the interactions between different patient groups and staff actions. A number of different types of models are available, however their underlying methods may prevent the representation of assisted evacuation. Many models can represent people with reduced mobility by modifying the walking speeds of agents but are not able to reflect the shape and increased footprint of devices, particularly in vertical evacuation, and the impact they might have on navigation, manoeuvrability, speed, and on the movement of the adjacent population. In particular, it is the size and shape of the assisted patient group that must be introduced into the evacuation flow. Applying data without explicitly representing the devices (i.e. using singular patients to represent stretchers, beds, wheelchairs, evacuation chairs, etc.) does not effectively capture these dynamics.
The next generation of microsimulation models is introducing assisted evacuation functionality based on research conducted over the past decade [8].These will provide valuable tools for the assessment of horizontal evacuation procedures in hospitals and for quantifying the time taken to prepare and move patients. Crucially, they also provide the means with which to test vertical evacuation strategies – something very difficult to assess given the problems with live drills.
What should we take away from all of this?
There is much work yet to be done to develop our understanding of assisted evacuation in hospitals. Clearly, research is needed into behavioural theory to characterise the factors at play and their interactions. Data is needed to quantify the impact of these factors and to futureproof our emergency planning and code development, to assess their performance before they are employed in reality. Models need to be developed, validated, and used cautiously in healthcare environments, to provide an evidence-base and a means of identifying problems and solutions. Codes need to reflect future demographics, and standards need to be developed for the performance of all movement equipment, not just wheelchairs.
In the meantime, we can use up-to-date developments in our practice. The latest data can be used to consider more realistic demographic profiles in hospitals and to assess the efficiency of mobility equipment. Given the great variability between the performances of different movement devices, we can use data to assess their suitability depending on the healthcare environment by considering the highest dependency population expected and the lowest staffing numbers available.
Microsimulation can be used to assess multiple scenarios at design stage or within operational environments. When used thoughtfully and where limitations are fully understood, this new technology can provide insight to better inform design and practice. It can evaluate both progressive horizontal evacuation and vertical evacuation, considering future service levels for staff-patient ratios and roles. It can also be used as a valuable training aid by providing a realistic picture of a live evacuation; something that is difficult to achieve during table-top exercises and walk-throughs.
We can never predict an evacuation outcome with certainty, but we can improve our methods of calculating mixed ability evacuation times by using the latest research into assisted evacuation. In many ways we have only scratched the surface of the issues faced in planning hospital evacuations. But in light of recent incidents, and to address the needs of our rapidly changing societies, we must review fire protection methods for vulnerable populations and work towards the serious consideration of full vertical evacuation in the risk assessments of the future.
Aoife is a managing consultant and hospital evacuation specialist at Movement Strategies, UK. She uses data analytics and simulation tools to assess pedestrian and evacuation movements in buildings and urban environments across the world.