MODELLING AND SIMULATION OF A PRE-HOSPITAL EMERGENCY CARE NETWORK USING TIMED COLOURED PETRI NETS
Pre-hospital emergencynetwork serves as a major gateway to the Accident and Emergency (AE) department of hospitals which is affected by overcrowding, and majority of projects studying pre-hospital emergency care networkdeal only with ambulance or firemanlocalisationas a means of addressing the problems confronting the Accident and Emergency (AE) department. However, this research work studied in detail the patient flow through the pre-hospital emergency care network. Taking into account not only fireman and private ambulances localisation, but also the otherservices performed in this network such as Emergency call service the service of the Emergency response teamusing Timed Coloured Petri Nets.
In developing a Timed Coloured Petri Nets (TCPN) model for a pre-hospital emergency care network, the emergency service of the State of Osun (O’ambulance) was used as a case study. The developed pre-hospital emergency care network (TCPN) model consists of five sub-modules. Arrival sub module modelled the arrival of emergency calls with different health cases. Sort call sub module modelled the call desk and how emergency calls are received by the available call desk agent (perm). Perm Decision sub-module modelled the decision of call desk agent (perm) based on the emergency cases. The rescue team (RT) Decision sub module modelled the decision and intervention of the Rescue team. While the Rescue-to-hospital sub-module modelled the transportation of victims to hospital. The developed TCPN model was simulated using CPN tools. The validation of the developed TCPN model was explored by carrying out the statistical analysis between the simulated and the observed emergency call cases under study.
The simulation results of the developed TCPN model revealed the number of emergency cases that require immediate and urgent response as 2, 6 and 19 while those that require no immediate response as 8, 22, 64 for the first, second and third simulations respectively. Revealing that some emergency calls require no immediate response and patients do not need to be taken to the hospital. Statistically, there were no significant difference between the simulated and the observed number of emergency cases that require immediate and urgent response.
Conclusively, this research work has been able to develop a TCPN model for studying a pre-hospital emergency care network. Also, the developed Timed Coloured Petri Nets model, through its simulation, could help in predicting the number of patients that do not need to be taken to the emergency department hence, reducing overcrowding in hospitals.
TABLE OF CONTENTS
Title page i
Table of Contents vi
List of Figures x
List of Tables ix
CHAPTER ONE: INTRODUCTION
1.1 General Overview 1
1.2 Statement of the Problem 2
1.3 Aim and Objectives 3
1.4 Significance of the Study 3
1.5 Scope of the Study 3
1.6 Methodology 4
CHAPTER TWO: LITERATURE REVIEW 5
2.1 Accident and Emergency 5
2.2 Accident and Emergency cases in Nigeria 5
2.3 Classification of Hospital 6
2.3.1 Clinic 6
2.3.2 Primary Health Care Centre 7
2.3.3 Comprehensive Health Care Centre (Medical Centre) 7
2.3.4 Secondary Health Care Centre(General Hospital) 7
2.3.5 Tertiary Health Care Centre(Special Hospital) 8
2.3.6 Teaching Hospital 8
2.4 Pre-hospital Emergency Service 9
2.5 Accident and Emergency Department/Unit 10
2.6 Modelling Pre-Hospital Emergency Care flow 11
2.7 Nature and Scope of Operation 14
2.8 Pre-Hospital Emergency Record 14
2.9 Pre-Hospital Emergency Patient Care Flow 18
2.9.1 Arrival at the Scene 18
2.9.2 Patient’s Safety 18
2.9.3 Initial Scene Assessment 19
2.9.4 Communication 19
2.9.5 Triage 19
2.9.6 Access to Patient 19
2.9.7 Packaging and Evacuation 20
2.9.8 Transport 20
2.9.9 Receiving Hospital 20
2.10. Emergency Triage 21
2.10.1 Benefits of Triage 21
2.10.2 Triage and the Colour Codes(The Health Traffic Light) 22
2.11 Challenges of Accident and Emergency Unit 22
2.11.1 Overcrowding 23
2.11.2 Management of Queues 24
2.11.3 Patient Waiting Times 25
2.12 Petri Net Concepts 26
2.13 Classesof Petri Nets 28
2.13.1 Classification of Petri Nets 29
2.13.2 High Level Petri Nets 29
126.96.36.199 Extension with Colours 29
2.14 Properties of Petri Nets 29
2.14.1 Behavioural Properties 30
2.14.2 Structural Properties 32
2.15 Modelling with Petrinets 32
2.15.1 Parallel Processes 33
2.15.2 Mutual Exclusion 34
2.15.3 Dataflow Computation 34
2.16 Transition Enabling and Firing Rules 35
CHAPTER THREE: RESEARCH METHODOLOGY 38
3.1 The Modelling Approach 38
3.2 The Developed Pre-Hospital System Model Marking Analysis 39
3.3 The Case Study 40
3.3.1 The Call Centre 41
3.3.2 The Rescue Team 41
3.3.3 O’ambulance Management 41
3.3.4 Fire Department 42
3.4 Model of the developed Petri Net 45
3.5 Declarations used for the Model 45
3.6 Data Collection 49
3.7 Data Analysis 49
3.8 The Developed Petri Net Model of Pre-hospital Emergency Care Network 52
3.8.1 Arrival 52
3.8.2 Sort Calls 52
3.8.3 Perm Decision 53
3.8.4 Rescue Team Decision 53
3.9 Validation of the developed TCPN Model 53
CHAPTER FOUR: RESULTS AND DISCUSSION
4.1 The Developed Petri Net Model Of Pre-Hospital Emergency 60
4.2 Simulation Result of the Developed Timed Coloured Petri Net Model of Pre-
Hospital Emergency Care Network 60
4.3 Validation Result of the developed TCPN Model of Pre-hospital Emergency Care
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 66
5.1 Conclusion 66
5.3 Contributions to Knowledge 66
5.3 Recommendation 66
Appendix O’Ambulance Services, State of Osun, Nigeria. 70
LIST OF FIGURES
2.1 Pre Hospital Emergency Care flow 18
2.2 Petrinet basic elements 28
2.3 Compact representation of a Petrinet 28
2.4 Petrinet representing parallel activities 33
2.5 Mutual Exclusion 34
2.6 Dataflow example 35
2.7 Mathematical and Graphical representation of Petrinet element 36
3.1 Flow diagram of O’ambulance Emergency care flow 43
3.2 Flow diagram of O’ambulance rescue team actions 44
3.3 Screenshot for the declaration for the Developed TCPN Model 46
3.4 Screenshot of arrival of rescue team 55
3.5 Screenshot of Sort calls 56
3.6 Screenshot of Perm decision 57
3.7 Screenshot of Rescue Team decision 58
3.8 Screenshot of Accident and Emergency at hospital 59
4.1 Screenshot of Rescue Team decision 61
4.2 Graph showing the variation in the two emergency cases 64
1 General Overview
The accident and emergency (AE) unit is one of the most sensitive and crucial departments in hospitals. Patients with severe conditions are admitted and treated without prior appointment and this department operate 24 hours a day, seven days a week. AE unit reason for being crucial can be accrued to the fact that it provides treatment to patients whose condition needs serious and immediate attention. The sensitivity of the unit is as a result of the fast and important decisions that needed to be made by the medical practitioners, who are to attend to numerous patients with diverse medical conditions ranging from accidents like food poisoning, fire burn and other emergency cases.
As a result of the nature of accident and emergency (AE) unit, it suffers from a lot of complexities, overcrowding and anomalies which must be paid attention to in order to deliver high quality care. AE unit overcrowding is due to many complex reasons that can be related to the pre-hospital emergency care network, the ED itself, or to the exit of the ED. Many studies tried to analyse this problem. Some of them deal with the improvement of the ED system (Yeh and Lin 2007). Other ones focus on the post-hospital care, especially the problem of allocation planning of hospital bed resources (Wang et al., 2007). Some other researchers are interested in studying the pre-hospital network emergency care which sorts out patient flow. In fact, a bad organization of this pre-hospital network may be an important cause of the ED overcrowding (Cotard 2002; La Cour des Comptes 2007).The majority of projects studying this network deal especially with ambulance or fireman localisation (Takeda et al. 2007). In this research work, a detailed study of the patient flow through the pre-hospital emergency care network was considered. Taking into account not only fireman and private ambulances localisation, but also the otherservices performed in this network such as Emergency call service
A model of the actual processes of pre-hospital care network was developed, since modelling plays a key role in complex system development. Modelling is the use of a simple, but explicit form to represent discrete event system. Timed Coloured Petri Nets (TCPN) was chosen to simulate the developed model.
2.1 Accident and Emergency
An accident is an unplanned or unscheduled event, it is the end result of a combination of events and circumstances which usually produces unintended suffering, injury, death or property damage (Naylor, 2000). An emergency is any injury or illness that is acute and poses an immediate risk to a person's life or long term health. A &E patients present with potentially life threatening symptoms such as headache, chest pain, abdominal pain, collapse of unknown cause and severe injury. Such patients have pressing need(s) (Amoah et al., 2011).
1.2 Statement of the Problem
In hospital, problems occur due to congestion and complexity in accident and emergency unit. A lot of anomalies such as overcrowding, long waiting time, and insufficient staffs coupled with wastage of available resources affect the treatment of patients and the overall clinical processes of the accident and emergency department(Joumana et al., 2011).
The previous area of research workstudying pre-hospital emergency care networkdeal only with ambulance or firemanlocalisationas a means of addressing the problems confronting the Accident and Emergency (AE) department. However, this research work studied in detail the patient flow through the pre-hospital emergency carenetwork. Taking into account not only fireman and private ambulances localisation, but also the otherservices performed in this network such as Emergency call service and the service of the Emergency response team. Timed Coloured petri nets (TCPN) was used to model the care flow in pre-hospitalnetwork.
1.3 Aim and Objectives
The aim of this research work is to model and simulatea pre-hospital emergency care network using Timed Coloured Petri Nets.
The specific objectives are to:
i. develop a Timed Coloured Petri Net (TCPN) model for a pre-hospital emergency care network using Osun State Emergency Service, Osogbo, as a case study;
ii. simulate the developed TCPN model using CPN tools;
iii. validate the developed TCPN model on the basis of the simulated and the measured emergency response rate.
1.4 Significance of the Study
In this field of study, a concept is not studied directly but through a model of the system. By the manipulation of the representation, it is hoped that new knowledge about the modelled system can be obtained without danger, cost or inconvenience of manipulating the real system itself. Thus, the developed Timed Coloured Petri Nets model through its simulation could help in studying and improving pre hospital emergency care service and hence, reduces overcrowding in Emergency department in hospitals.
1.5 Scope of the Study
In this research work, Osun State Emergency Service, was considered, having thirty ambulance vehicle distributed across the thirty Local Government of the State, with four ambulance vehicle stationed in strategic places in the State Capital, Osogbo.Timed Coloured Petri Nets was mainly used to model the pre-hospital emergency care network with the use of CPN tools to simulate the model. Validating the developed TCPN model on the basis of the simulated and the measured emergency response rate
The methods of the study employed in this research work are as follows:
i. Establishment of a theoretical foundation for the research through a sound literature review.
ii. Identification of pre-hospital emergency care network process.
iii. Discussion and Collection of record from pre-hospital emergency management.
iv. Development of a model for the process.
v. The developed model was simulated three times using Timed Coloured Petri Nets tools..