BOOKS OF RtfiDIfGS - PAHO/WHO

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HANCOCK Table 1. Parameters Varied for Simulation of
ET AL
Hospital with Five-Day Scheduling to Determine
Maximum Average Occupancy at 40, 80, 120,
160, and 200 Beds
Phase 2
Phase I
E1%~'~ % ~
EMfG scheduled
Mean
emeremnc
LOS
Mean
elecotuve
LOS
acheduled
30 40, 70, 90 5.1 43 40, 70. 90
50 40,70,90 10.4 8.4 40,70.90
66 40,70.90 14.9 13.1 40,70.90
95 0
In the second phase of the study, the effects of mean LOS on maximum
average occupancy were investigated. Percent EMG was held
constant at 50 percent and patients were scheduled five days a week.
Again, the number of beds was varied over the same five levels. Within
each level, mean LOS and percent scheduled were also varied as shown
in Table 1.
In the third part of the study, the effect of scheduling seven days
a week rather than five was investigated. Percent EMG was held constant
at 50 percent and the emergency and elective LOS means were
10.38 and 8.39 days, respectively. The number of beds was again varied
over 40, 80, 120, 160, and 200, and percent scheduled was varied
over 40, 70, and 90 percent.
A Fortran simulation program developed by Hamilton, Hancock,
and Hawley [11] was used. This program embodies the rules of the
ASCS and allows much flexibility in modeling different hospital and
facility settings. The simulator has been documented and validated
[5,11], but an attempt was made here to estimate the magnitude of
possible errors involved in the simulation process.
The parameters percent emergencies and percent scheduled are
not directly controllable through the input but are dependent on the
number of call-ins that occur. Thus a search procedure is involved in
which the inputs are varied until the proper levels of the parameters
are approximated and the turnaway and cancellation constraints are
satisfied. Once this is accomplished, the allowances are varied until
the maximum average occupancy at the given parameter levels is
determined. This procedure causes two possible sources of error.
It is impossible to set all of the parameters exactly at the specified
levels. Percent emergencies and percent scheduled are generally
within -2 percent of the assigned level, and the error that this induces
in maximum average occupancy may be estimated from the
HEALTH results using linear interpolation. For example, Fig. 2b shows that in
XUEACI
K a facility with 40 beds. a change of 30 percent in percent scheduled
results in a change of 6.5 percent in maximum average occupancy.
Thus an error of 2 percent in percent scheduled would cause an error