BOOKS OF RtfiDIfGS - PAHO/WHO

- 237 -
HANCOCK
ET AL Fig. 4. Maximum average occupancy vs. number
of beds with 95 percent emergency arrivals and
all electives called in.
o95
100oo
90
85
0% CH
0 50 75 o00 125 150 175 200
NUMBER OF BEDS
below. Perhaps it would be desirable to use Fig. 4. as a benchmark
when examining the remaining figures since it is closest to the historical
Poisson arrival process.
In all cases, maximum average occupancy increases with increasing
facility capacity. The higher percent occupancy in larger facilities
results from a decreasing coefficient of variation of census (standard
deviation/mean) as the number of beds increases. When the coefficient
of variation is small, the maximum average mean census may be
doser to the facility-capacity while still maintaining the turnaway
and cancellation constraints.
For a given number of beds maximum average occupancy is observed
to increase with decreasing percent scheduled. This is a result
of the fact that as percent scheduled decreases, the number of call-ins
is increased. Thus the ability of call-ins to reduce census variance is
improved as percent scheduled decreases.
In this study when patients are scheduled five days a week, a lack
of call-ins is felt most heavily on weekends. With no patients scheduled
for Friday and Saturday, it is necessary to call patients in to
maintain a high maximum average occupancy. If the call-ins are
unavailable due to a high percent scheduled, a weekend drop-off in
average occupancy occurs. (Remember that the ratio of call-ins to
scheduled patients is constant.)
In most cases, maximum average occupancy is observed to increase
as percent EMG decreases. This is because, in general, emergency
arrivals introduce a greater variance in the census than elective arrivals.
In certain cases, however, this is not true. In this study, when
percent scheduled is 90 percent, the variance in census caused by elective
admissions is larger due to the drastic weekend drop-off in averlHELTH
age census. Thus, when percent scheduled is high and patients are
ReIEARCH scheduled five days a week, maximum average occupancy will decrease
as percent EMG decreases and the percent of elective patients
increases.