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.
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 .
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) . 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
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 . 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
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
, 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  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
The next generation of microsimulation models is introducing
assisted evacuation functionality based on research conducted over the past
decade .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 Hunt, Ph.D
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.