BOOKS OF RtfiDIfGS - PAHO/WHO

160
I indicates the flow of patients through the department.
Many of the patients are scheduled. Experience
has shown that the scheduled paticrts will either arrive
and enter the department too early, or will arrive too late.
Scheduled inpalients are assisted by orderlies to arrive at
I)RD in 20 min, depending on lile ivailability of clevators.
Due to these random elements, it is assumcd l:al the
patients enter the DRD with an interarrival distribution
time of f(t); with probability P, of being an outpatient,
and wilh prohahility I - P, of hcing an inpatient. The
inpatients will wait for ocie of I¡le ¡enl orderlies (Ot : 1(1)
for assistance to be taken to the control desk by one of
three means of transportation; walking, wheelchair and
stretcher with probabilities P2, P 1, P,, respectively. An
oulpalient reporis to thc reception Jcsk itt which inme the
individual is serviced for time r,. A fraction P5 of the
outpatients will change to a hospital gown which takes time
r2 if one of the dressing rooms (DR = 16) is ava!lNble. The
outputient then reports lo the control desk and sNpends time
,t. Each patient using thc dressing rooms will lock ¡he
room for the entire period of the examination and therefore
prevent others from utilizing the room until the individual
is released.
At a typical DRD, Ihere are over 200 different types of
examinations which can be grouped into 13 major
categories with minor variations within a category.
For the most part, however, the demand for the
different radiographic examination will vary over the day.
Gl. BE and IVPt are performed during the morning hours
before the patient has eaten; while a Myelogram is usually
scheduled for the afternoon.
Table 2 presents a list of the 13 examinations with the
corresponding mean examination time 74, and the range
for cach category. Pi(j) is the probability of having
examination type j at period i = (8-10 a.m.), i=2
(10 a.m.-12 p.m.), i = 3 (12-2 p.m.), i =4 (2-4.30 p.m.).
The patient is then assigned an Examination Room
(ER= 14), at the control desk. This assignment is an
important one since it determines the length of stay for
that patient in the queue. The DRD at Temple is one
where not all examination rooms are equipped with the
tExp'anations of category names are given in Table 2.
R u. IrV orr
,, nl
Table 1. List and explanation of variables
inpalient, l Ool...n.I
.- 109 -
1d,--. v 1 C-l'eI - ( ,*
Th Wpellntait lo o r n po Dcesng it r
Fi1. nrow. Maeporflol owharl tpatien
Tjma
sam facilities, and oy cenain rooms can prformrly
specific examinations. Most of the examinations require
one of the Technicians (TE= 10), while other rooms
require radiologists. When the examination is completed.
the patient waits time as for film processing with the
probability P6 that the individual may need additional
films to complete the study. If supplementary films are
necessary, the patient then returns ¡o the control desk
with high priority. If the study is adequate, the outpatient
is released, and the inpatient will wait for an orderly to be
returned ¡o the room which takes time Te.
EVALiJAiON OF SUCH A SYSTEM
It is important to recognize that in most large systems,
there is mnore than one measure of performance. Thus, it is
not surprising that in this case there are several, some
Vt..' i.lMl, ' -xp i .na11It'on DI i lelstill ¡nll
f (t)
Inter Arrival Time letween Two Patienta
rl Service Time At Reception Desk
,t 2 . eDressing Time
r3 Servicr Time At Control Desk
T'1 Examination Time
y5 Iíilm Process Timne
(Walk
T1 t ~Trau.,lorlotion
Time To or rroma ~ ielechair
1'.- IhgUinrlmelll r
iStretcl.lr
P1'
k' S
I''rceintoge Of Outpatients
Ierentage Of Walk/ Wichelehair/ Stretcher
l'ercentage Or Outputients Needing Dressing Room
p; PGl'.ce'tag Of' I etrlntu N ti.dilg Adlitinoial tilm
ER í ,,I:xtnll Jtoll NoOmS
OR Orderlier
TE Technicians
DR Dressing Rooms
Un 1 unm
Uniform
Uniform
Constant (t1 lin.)
See TabLc 2
Constant (10 Hill.)
Unfarorn
Uniform
Uli fornm
45X (55% lnpatlent)
5/20/7W%
803
llI
10
16