BOOKS OF RtfiDIfGS - PAHO/WHO

- 240 -
vallie in thc sensitivity analysis of the cancellation and turnaway SIMULATION
constraint. OF HOSPITAL
OCCUPANCY
Application of Results in Facility Sizing
-The results of this study may be applied in determining the correct
size of a hospital. The method is as follows.
A. Obtain an estimate of the average daily census (ADC) of the
facility. For planning purposes, this is frequently obtained by
taking the present ADC and adjusting for demographic factors
over thc planning horizon.
B. Estimate the parameters for the facility (percent EMG, percent
scheduled, mean LOS, and scheduling pattern). The usual
assumption is that the percentages will not change over the planning
horizon.
C. Find the graph in Figs. 2-5 that is closest to the parameters
estimated in B above.
D. Determine the necessary number of beds (NB) using successive
approximations as follows.
1. Use ADC as an initial estimate of the number of beds, and
determine a percent occupancy from the appropriate graph.
2. Determine the number of beds needed using NB = ADC/
(% occupancy/100).
3. Use the number of beds found in step 2 to determine a
revised percent occupancy.
4. Return to step 2 and compute a new NB using the revised
occupancy of step 3.
5. Repeat steps 2, S, and 4 until the bed-number estimates
converge.
Use of the algorithm described above assumes, of course, that the
ASCS system will be used to admit patients to the facility. The specific
schedules, CRA and CA, which are specific for day of the week,
can be quickly obtained using the admissions simulator. These values,
of course, will vary for any point on the particular curve used.
As an example, consider a facility with average daily census =
180.0, percent EMG = 66, and percent scheduled = 70. To determine
the optimal number of beds, find the occupancy estimate Of 96.3 percent
from Fig. 2b using number of beds = 180. Then,
NB = 180.0/(96.3/100) = 186.9
This rounds to 187 beds. Figure 2b gives the occupancy estimate of
96.5 percent for 187 beds. Thus the second estimate of beds is
NB = 180.0/(96.5/100) = 186.5
This again rounds upward to 187 beds, the sequence has converged,
and the optimal number of beds of such a facility is 187.
The results of this study should not be extrapolated to small
(fewer than 40 beds) facilities, which should be simulated individually
sinc. percent occupancy is extremely sensitive to the number of beds
in the facility.