Dynamics of bed use in accommodating emergency admissions: stochastic simulation model

Editor - Bagust et al’s simulation model suggests that failure to provide a
bed for patients in acute NHS hospitals in England should be infrequent at
current annual occupancy levels (79.5% in 1997-98)[1]. In the absence of
published data, their model corresponds to most clinicians’ experience.

Their projection of rapidly rising annual occupancy levels for all
acute specialties “which could exceed 90% by 2002-03” is implausible.
Average occupancy in acute specialties in Scottish NHS hospitals has risen
slowly because rising numbers of emergency and elective admissions and
falling bed capacity have been accompanied by falling average lengths of
stay[2]. Average occupancy rose by only 4.6% between 1980-98 (Table).
While occupancy statistics in English NHS hospitals are limited to 1996-97
and 1997-98 (79.5% in both years), long-term English and Scottish
occupancy trends are likely be similar[3]. In this respect the authors’
simulation model conflicts with past experience.

In the absence of total closure, the frequent disruption experienced
by patients and staff in acute hospitals at periods of high occupancy
results from long waits in Accident & Emergency Departments due to
delays in finding scarce beds and from the frequent failure to accommodate
patients in their consultants’ parent units. This leads to their
dispersal within the Medical Directorate (since most emergency admissions
are medical), extending to their wider distribution in other directorates
as occupancy rises. Long ward rounds to multiple wards and the
cancellation and postponement of elective surgical procedures follow,
contributing to rising stress levels in medical and nursing staff and
rising waiting lists. Far from planning to increase reserve bed capacity
as Bagust et al sensibly suggest, new hospitals being built by the Private
Finance Initiative will contain about 30% fewer acute beds than those they
replace[4].

In the absence of increased reserve bed capacity, our experience
suggests that pressures on acute beds can be alleviated by the appointment
of experienced senior nursing staff as bed managers with wide
responsibilities for the direction of inpatient “traffic” and for the
implementation of effective discharge planning policies.

TABLE

Changes in inpatient activity in acute specialities in Scottish NHS
hospitals between 1979 - 80 and 1997 - 98.

Year         Inpatient    Average 
             discharges   staffed beds
1979 - 80    508,360      18,144
1997 - 98    751,543      12,136
Change %     + 47.8       - 33.1

Year	    Mean stay       Occupancy
            (days)          (%)

1979 - 80     10.8            71.9
1997 - 98      5.1            75.2
Change %    - 52.8           + 4.6

REFERENCES

1. Bagust A, Place M, Posnett J W. Dynamics of bed use in
accommodating emergency admissions: stochastic simulation model. BMJ
1999; 319: 155-8.

2. Scottish Health Statistics. Edinburgh: NHS (Scotland)
Information and Statistics

Division, 1980-98.

3. Department of Health. Bed availability and occupancy. England,
financial year

1997-98. London: DOH 1998.

4. Pollock A M, Dunnigan M G, Gaffney, D, Price D, Shaoul J. The
private finance

initiative. Planning the “new” NHS: downsizing for the 21st
century. BMJ, 319: 179-84.

Matthew G. Dunnigan
Senior Research Fellow
Department of Human Nutrition, Royal Infirmary Glasgow G31 2ER

Myra M. McMurdo
Discharge Co-ordinator
Stobhill Hospital, Glasgow G21 3UW

18/7/99

The Editor,
British Medical Journal,
BMA House,
Tavistock Square,
London. WC1H 9JR

EDITOR - I agree that a simulation model as described by Bagust et al
1 using a spread sheet is a valuable way of investigating the dynamics of
bed use. We have already described a similar system using a Smartware II
spreadsheet that showed the dynamic use of beds in an obstetric and
gynaecology unit. 2 Obstetrics inevitably has a high percentage of
"emergency" admissions.

In 1992 following the Changing Childbirth report there was increasing
pressure to reduce the size of the estate and the bed complement. The
required bed complement estimated from historical bed occupancy rates,
from other comparable units or calculated from simple formulae often lacks
credibility with clinicians. The dynamic spreadsheet approach allows "what
if" scenarios to be entered and can take into account variations in length
of stay, Caesarean section rates and community visits etc, and the staff
requirements for the level of activity. Too many beds leads to inefficient
use of resources while too few requires finding beds in other parts of the
hospital during periods of high admissions and the associated risks to
patients that this involves. We showed that such a model was a valuable
tool in change management, and it has proved a realistic simulation for
bed requirements since the change in bed numbers has been effected.

David J R Hutchon
Consultant Obstetrician & Gynaecologist

References

1 Bagust A, Place M, and Posnett J W. Dynamics of bed use in
accommodating emergency admissions: stochastic simulation model. British
Medical Journal 1999;319:155-8

2 Hutchon D J R. Using computer modelling for the rationalisation of
hospital beds. British Journal of Health Care Management 1997;3(6):332-4