Using Computer Simulation to Study Hospital Admission and Discharge Processes

100 Pages·2014·1.12 MB·English

by  Edwin S. Kim

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Masters Theses 1911 - February 2014
2013
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Edwin S. Kim
University of Massachusetts Amherst
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USING COMPUTER SIMULATION TO STUDY HOSPITAL
ADMISSION AND DISCHARGE PROCESSES

A Thesis Presented
By
EDWIN S. KIM

Submitted to the Graduate School of the
University of Massachusetts Amherst in partial fulfillment
of the requirements for the degree of

MASTER OF SCIENCE IN INDUSTRIAL ENGINEERING AND OPERATIONS RESEARCH

September 2013
Department of Mechanical and Industrial Engineering
© Copyright by Edwin S. Kim 2013
All Rights Reserved
USING COMPUTER SIMULATION TO STUDY HOSPITAL
ADMISSION AND DISCHARGE PROCESSES

A Thesis Presented
By
EDWIN S. KIM

Approved as to style and content by:
Hari Balasubramanian, Chair

Philip Henneman, Member

Ana Muriel, Member

Donald L. Fisher, Department Head
Department of Mechanical and Industrial Engineering
ACKNOWLEDGMENTS

I’d like to first thank my Lord and savior Jesus Christ for giving me the opportunity,
strength, and ability to pursue this research topic. I have been blessed in so many ways and hope
to glorify him through all that I do.
My thesis advisers Professor Hari Balasubramanian and Dr. Philip Henneman have from
the beginning been wonderful in their guidance throughout this process. I am so grateful for their
advice and my thesis would not have finished without their integral support. I would like to also
take the time to acknowledge Professor Ana Muriel for her helpful comments and being on my
committee.
To my family, my brother, mother, and father, my greatest support group, I am so
thankful for the love you have given me. I cannot express in words my gratitude.
I would like to also thank all of my peers, who have always been there and have made
special bonds together.
I am truly blessed to have such wonderful people in my life. Thank you all.
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ABSTRACT
USING COMPUTER SIMULATION TO STUDY HOSPITAL ADMISSION AND
DISCHARGE PROCESSES
SEPTEMBER 2013
M.S.I.E.O.R., UNIVERSITY OF MASSACHUSETTS AMHERST
Directed by Professor Hari Balasubramanian

Hospitals around the country are struggling to provide timely access to inpatient beds. We
use discrete event simulation to study the inpatient admission and discharge processes in US
hospitals. Demand for inpatient beds comes from two sources: the Emergency Department (ED)
and elective surgeries (NonED). Bed request and discharge rates vary from hour to hour;
furthermore, weekday demand is different from weekend demand. We use empirically collected
data from national and local (Massachusetts) sources on different-sized community and referral
hospitals, demand rates for ED and NonED patients, patient length of stay (LOS), and bed
turnover times to calibrate our discrete event simulation model. In our computational
experiments, we find that expanding hours of discharge, increasing the number of days elective
patients are admitted in a week, and decreasing length of stay all showed statistically significant
results in decreasing the average waiting time for patients. We discuss the implications of these
results in practice, and list the key limitations of the model.

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TABLE OF CONTENTS
Page
ABSTRACT ..................................................................................................................................... v
LIST OF TABLES .......................................................................................................................... ix
LIST OF FIGURES ......................................................................................................................... x
CHAPTER
1. INTRODUCTION ...................................................................................................................... 1
1.1 Motivation ........................................................................................................................ 1
1.2 Background ...................................................................................................................... 1
1.3 Discrete Event Simulation ............................................................................................... 2
1.4 Problem of Description .................................................................................................... 3
2. LITERATURE REVIEW ........................................................................................................... 6
2.1 Admission Scheduling ..................................................................................................... 6
2.2 Elective Admission .......................................................................................................... 9
2.3 Emergency Department ................................................................................................. 11
2.4 Computer simulation in health care processes ............................................................... 13
3. METHODOLOGY ................................................................................................................... 16
3.1 Baseline parameters ....................................................................................................... 16
3.1.1 Replication Parameters .......................................................................................... 16
3.1.1.1 Number of Replications ................................................................................ 17
3.1.1.2 Warm Up Period .............................................................................................. 17
3.1.1.3 Replication Length ............................................................................................ 19
3.1.1.4 Replication Start Date and Base Time Units..................................................... 21
3.1.2 Uncontrollable Parameters ..................................................................................... 21
3.1.2.1 Type of Hospital ............................................................................................... 22
3.1.2.2 Hospital Patient Make Up ................................................................................. 23
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3.1.2.3 Length of Stay (LOS) ........................................................................................ 24
3.1.2.4 Weekly Arrival Rate ......................................................................................... 28
3.1.2.5 ED Patient Arrival Distribution ........................................................................ 29
3.1.3 Controllable Parameters (CP) ................................................................................ 35
3.1.3.1 Number of Beds ................................................................................................ 35
3.1.3.2 NonED Admission Rates .................................................................................. 36
3.1.3.3 Patient Discharge Hours.................................................................................... 38
3.1.3.4 Bed Turnover Time ........................................................................................... 38
3.1.3.5 Patient Priority .................................................................................................. 39
3.2 Modified Parameters ...................................................................................................... 40
3.2.1 Patient Discharge Times ....................................................................................... 40
3.2.2 Allowable days of arrival for NonED patients ...................................................... 41
3.2.3 Patient length of stay ............................................................................................. 42
3.3 ARENA Model .............................................................................................................. 42
3.3.1 Patient Arrival ....................................................................................................... 43
3.3.2 Waiting for Bed Queue ......................................................................................... 44
3.3.3 Patient Receives Care in Bed ................................................................................ 47
3.3.4 Patient Discharge .................................................................................................. 47
4. RESULTS ................................................................................................................................. 49
4.1 Baseline Parameters ....................................................................................................... 49
4.2 Peaks and Valleys .......................................................................................................... 52
4.3 Patient Discharge Times ................................................................................................ 52
4.3.1 75 bed community hospital ................................................................................... 53
4.3.2 150 bed community hospital ................................................................................. 54
4.3.3 150 bed referral hospital ....................................................................................... 56
4.3.4 300 bed referral hospital ....................................................................................... 57
4.4 Allowable day of arrival for NonED patients ................................................................ 58
4.4.1 75 bed community hospital ................................................................................... 59
4.4.2 150 bed community hospital ................................................................................. 61
4.4.3 150 bed referral hospital ....................................................................................... 62
4.4.4 300 bed referral hospital ....................................................................................... 64
4.5 Patient length of stay ...................................................................................................... 65
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4.5.1 75 bed community hospital ................................................................................... 65
4.5.2 150 bed community hospital ................................................................................. 67
4.5.3 150 bed referral hospital ....................................................................................... 68
4.5.4 300 bed referral hospital ....................................................................................... 70
5. DISCUSSION ........................................................................................................................... 72
5.1 Summary of Results ....................................................................................................... 72
5.2 Transparency and Validation ......................................................................................... 74
5.2.1 Face Validity .......................................................................................................... 74
5.2.2 Verification ............................................................................................................ 75
5.2.3 Cross Validation ..................................................................................................... 76
5.2.4 External Validation ................................................................................................ 77
5.3 Limitations ..................................................................................................................... 78
5.3.1 Input parameters ..................................................................................................... 78
5.3.2 ARENA Limitations .............................................................................................. 80
5.3.3 System Limitations ................................................................................................ 81
6. CONCLUSION ......................................................................................................................... 83
APPENDIX: FULL ARENA MODEL .......................................................................................... 84
BIBLIOGRAPHY .......................................................................................................................... 85

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LIST OF TABLES
Table Page
1. Mass hospital percentage of admission in 2010 ....................................................................... 23

2. Baseline percent admission for community and referral hospitals ......................................... 24

3. Arrival rate chart based on hospital size ................................................................................. 29

4. Two hours with percentages of events occurring with a Poisson distribution
compared to actual events during a 1 year simulation run ............................................................. 34

5. Baystate Medical Center bed cleaning time statistics ............................................................. 39

6. ED and NonED waiting times comparing hospital types using baseline values ..................... 51

7. ED and NonED wait times comparing discharge times
for a 75 bed community hospital ................................................................................................... 54

8. ED and NonED wait times comparing discharge times
for a 150 bed community hospital.................................................................................................. 55

9. ED and NonED patient wait time comparing discharge times
for a 150 bed referral hospital ........................................................................................................ 57

10. ED and NonED patient wait time comparing discharge times
for a 300 bed referral hospital ........................................................................................................ 58

11. ED and NonED wait time comparing NonED arrival schedule
for a 75 bed community hospital ................................................................................................... 60

12. ED and NonED patient wait time comparing NonED arrival schedule
for a 150 bed referral hospital ........................................................................................................ 63

13. ED and NonED patient wait time comparing NonED arrival schedule
for a 300 bed referral hospital ........................................................................................................ 65

14. ED and NonED patient wait time comparing LOS for a 75 bed community hospital ........... 66

15. ED and NonED patient wait time comparing LOS for a 150 bed community hospital ......... 68

16. ED and NonED patient wait time comparing LOS for a 150 bed referral hospital ............... 69

17. ED and NonED patient wait time comparing LOS for a 300 bed referral hospital ............... 71

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