A mass-casualty incident (MCI) is an event that generates more patients at 1 time than locally available resources can manage through routine procedures. MCIs result from multiple causes which include ‘conventional MCIs’ (transportation incidents, burns, and severe weather events); exposure to chemical, biological, radiological, or nuclear agents due to an unintentional or accidental release or act of terrorism; and catastrophic health events (major explosions, major hurricanes, influenza pandemics, and others). With regards to MCIs, it seemed natural to think about disasters. Disasters are incidents where more than 10 people are killed or more than 100 are affected. ¹ Disasters are the main cause of MCIs. Global trends indicate that the frequency of disasters worldwide have doubled, as disaster hazards are on the rise. ^{Reference Swienton and Raymond2} Over the last 20 years, 7348 disasters were recorded by the Emergency Events Database (EM-DAT), and these disasters claimed approximately 1.23 million lives, with an average of 60000 deaths per annum. ³ MCIs are classified according to different levels depending on the number of victims: Level 1 = 5 - 10 victims, Level 2 = 11 - 20 victims, Level 3 = 21 - 100 victims, Level 4 = 101 - 1000 victims, and Level 5 = over 1000 victims. ^{Reference Busby4}

In order to cope with MCIs, exceptional emergency arrangements and additional or extraordinary assistance are required ^{Reference Lomaglio, Ansaloni, Catena, Sartelli, Coccolini, Kluger, Coccolini, Catena and Ansaloni5} ; this is referred to as surge capacity. Surge capacity is a critical component of preparedness ^{Reference Barbisch and Koenig6} ; it describes the ability of a health system to respond to a sudden increase in patient care demands. ^{Reference Hick, Koenig, Barbisch and Bey7} In addition, surge capacity includes the staff, structure, and system (4S) that can help to develop optimized sustainable surge capacity. ^{Reference Hick, Koenig, Barbisch and Bey7} Based on the 4S system, Hick et al. proposed the CO-S-TR tool, which can be incorporated into job action sheets or can stand alone as a reference or poster. ^{Reference Hick, Koenig, Barbisch and Bey7} The CO-S-TR includes 3 main elements, each of which contains 4 sub elements (Figure 1). In addition, a brief, facility-specific mobilization checklist is designed to enable the rapid identification and prioritization of resource needs, the recognition of key objectives, and early stages of incident control. The tool provides a means to proactively determine what resources are needed and how to deploy them to minimize omissions and optimize outcomes. It is a practical tool for emergency response or surge capacity education. As suggested, the integrated and efficient response can only come about if the personnel involved are educated and trained in the unique procedures thought to be necessary in the response to these incidents. ^{Reference Lomaglio, Ansaloni, Catena, Sartelli, Coccolini, Kluger, Coccolini, Catena and Ansaloni5} With regard to the emergency response training of MCIs, exercises are indispensable.

Figure 1. The CO-S-TR framework.

An exercise is a focused practice activity that places participants in a simulated situation requiring them to function in the capacity that would be expected of them during a real event. ⁸ By testing policies, plans, and training personnel, exercises for MCIs could help ensure that the organization or individuals is in a constant state of well-prepared readiness. ^{Reference Moss and Gaarder9} To improve the surge capacity of medical institutes, comprehensive exercises are indispensable. There are 5 main types of comprehensive exercises: orientation seminars, drills, table-top exercises (TTXs), functional exercises, and full-scale exercises. ⁸ TTX acts as a bridge between simple and complex, narrow and broad, least expensive, and most costly to implement, and theoretical and realistic. In a TTX, the participants come together to take on their roles and work through an incident. The participants examine and resolve problems based on existing operational plans. They also identify where those plans need to be refined. The major elements of a TTX include policy-level personnel evaluating plans and procedures, resolving coordination and responsibility questions, and facilitating group discussion. Such exercises provide participants with an emergency scenario to analyze, thereby increasing their awareness of the roles and responsibilities of individuals who need to respond to, stabilize the situation, neutralize threats, and help others recover from emergencies. They are designed to prompt constructive discussion about existing emergency response plans as participants identify, investigate, and resolve issues. These features make TTXs a common training activity used during emergency preparedness and disaster education. The TTX is classified as a discussion-based exercise with little or no practice. In this study, we tried to reform the TTX by inviting the participants to discuss and respond in a simulated scenario. In recent years, a specific type of TTX has involved the use of reports and details from recent MCIs to challenge and assess a healthcare system or institution. ^{Reference Moss and Gaarder9–Reference Skryabina, Betts and Reedy12} This type of TTX was proven to be valuable in testing plans and informing policy and practice during incidents. ^{Reference Hirsch, Carli and Nizard13} Therefore, we developed a TTX training based on a real event that occurred in Shanghai in recent years, namely, a crush that occurred in Shanghai’s historic Bund district on December 31, 2014, that killed 36 people and injured 49 others. ¹⁴ The crush was categorized as a level-3 MCI. It is a representative MCI that happened in a megacity with tremendous social influence. The event was such as could arouse the participants’ memory and interest. The crush may also have triggered surge capacity of different level for some hospitals based on the status of shunted casualties. The healthcare system experienced challenges in its ability to provide an effective and coordinated response to this MCI in Shanghai. This tragedy highlighted the need for cohesive strategies that focus on management systems for major public health and medical responses. In this study, we aimed to develop a TTX training program based on this event, to apply it in practice, and to evaluate it.

Even though functional or full-scale exercises have many benefits, they are undoubtedly difficult for recently graduated medical staff to accomplish. The TTX allows for easy adaptability for various programs, departments, and disaster scenarios. ^{Reference Sena, Forde and Yu15} This makes it a suitable tool for senior medical students or newly graduated medical staff. According to the National Disaster Life Support course manual, disaster exercises should be designed to test incident command and control, communications, logistics, laboratory coordination, and clinical capabilities, among others. ^{Reference Swienton and Raymond2} This idea is consistent with the CO-S-TR model. Therefore, we tried to develop a scenario simulation TTX kit based on the CO-S-TR model and to evaluate the effectiveness of the TTX training among recently graduated medical staff in this study.

Development of the TTX program

The purpose of a TTX is to strengthen or evaluate readiness to manage a health emergency through facilitated group discussions. Therefore, it is paramount that exercises are designed to focus on issue areas that require concrete decisions over a limited period. The design and implementation of a TTX program determine its success or failure. In order to ensure the quality of the program in this study, a design group of 4 researchers with ample emergency care teaching experience was recruited, and these researchers took charge of the program development.

First, information on the sequence and casualties of the Shanghai New Year crush was collected through a literature review. A brief timeline of the incident was drawn. After the TTX protocol was drafted, an expert conference was held to discuss the purpose, content, format, and details of the program. Furthermore, the TTX program was based on the CO-S-TR model, ^{Reference Hick, Koenig, Barbisch and Bey7} involving elements C4, S4 and T4. All 12 CO-S-TR elements were addressed within the TTX scenario. It was designed according to the 8 TTX design steps proposed by the World Health Organization: assess needs, define the scope, write a purpose statement, define objectives, compose a narrative, write major and detailed events, list expected actions, and prepare messages. ⁸ The core objectives that the participants were expected to achieve at the end of the TTX program were set according to the SMART (simple, measurable, achievable, realistic, and task oriented) system. The primary purposes of the TTX program are as follows: to strengthen and evaluate first aid strategies for MCIs (the participants are required to choose the proper first aid technique for each injury and attach the measure card to the injury models), to learn and verify management skills for MCIs, and to formulate and validate the assumptions and procedures for an emergency response plan.

The TTX training program contains 2 parts: the on-scene emergency response and the in-hospital emergency response. The in-hospital part is divided into 3 stages: mild, moderate and severe surge status (Figure 2). During the on-scene response part, a frontline medical team with 7 crews is supposed to respond within 5 minutes after the initial crush. This part mainly focuses on site control: triage, emergency treatment, and transport are the key points, and emergency incident management on scene is another teaching element. In the in-hospital part, each stage corresponds to different surge levels. The parameters of the hospital beds, the extensible resources of each department and all kinds of medical resources are provided before the exercise, and the participants should deal with the injuries based on the available resources and the possible capability of overload. The injuries’ total needs will exceed the resources step-by-step. As the first batch of casualties arrives, the hospital enters the mild surge stage, and the resources of the emergency department should be mobilized to meet the demands. As the second batch of casualties arrives, the resources of the emergency department cannot meet the demand, and the whole hospital should be mobilized. As the third batch of casualties arrives, all hospital resources should be utilized. The extended capability of the hospital should be explored, and outside resources should be sought. All the casualties arrive at an increasing frequency. Once the injured patients arrive, the ambulance sirens continue to sound until the injuries are managed properly, while the instructors urge the participants to respond quickly to create tension. As the participants proceed through the event, they experience different degrees of overload and implement an emergency response accordingly.

Figure 2. The TTX process.

To ensure the effectiveness of the training program, all instructional props were designed and made specifically for the program (Figure 3). Diagrams of the layouts of the Bund district and the hospital were drawn by designers according to their actual layouts. The casualty models were made of acrylic with precast magnets and were designed to be able to stand, sit and lie down. In addition, the injury information cards, and emergency measure cards were all made of magnetic material so that they could be attached to the casualty models. The instructional props recreated the scene of the crush event and simulated all the injuries as much as possible. The instructors acted as bystanders, members of the media, and family members of injured patients so that the participants could practice in an authentic environment.

Figure 3. Instructional props.

Evaluation of the TTX program

Sample

Recently graduated medical staffs were recruited by convenience sampling, and all the medical staff voluntarily participated in this study.

Instruments

Self-designed questionnaire

Demographic items collected information on the participants’ gender, age, MCI training experience, and MCI response experience. In addition, a program evaluation questionnaire with 7 items was developed by the research group, focusing on both the degree of willingness for involvement and the perceived likeability of the TTX. The instructional props were evaluated on a 5-point scale ranging from highest involvement/willingness to lowest involvement/willingness or from strong dislike to strong like. The difficulty ratings of the TTX ranged from extremely easy to extremely difficult, and a score of 3 represented moderate difficulty.

Simulation design scale (SDS)

The SDS is a 20-item, 5-point Likert-scale instrument with 2 dimensions: the appropriateness of the researcher-developed simulations and the most important features of the simulations. ^{Reference Jeffries16} The SDS was translated into Chinese and was found to have good properties in terms of the presence of features, r = 0.88, and the importance of features, r = 0.89. ^{Reference Wang, Fitzpatrick and Petrini17}

Educational practices in simulation scale (EPSS)

The EPSS is a 16-item, 5-point Likert tool used to measure the extent to which best practice principles in education are used in TTXs. The elements evaluated in the EPSS scale are active learning (10 items), diverse ways of learning (2 items), high expectations (2 items), and collaboration (2 items). The EPSS was translated into Chinese and was found to have good properties in terms of the presence of features, r = 0.87, and the importance of features, r = 0.94. ^{Reference Wang, Fitzpatrick and Petrini17}

Intervention and procedure

An experienced instructor who was familiar with the TTX was primarily in charge of the training course. Another 2 instructors were assigned to act as recorders, documenting actions taken during the TTX. The TTX began with a briefing to orient the participants to the TTX objectives, ground rules, communication, and simulation procedures. The scenario narrative was then presented in an intelligence briefing. The scenarios generally described the New Year’s Eve crush in Shanghai, taking the participants back to the ‘chaotic scene’ in Shanghai’s historic Bund district and the emergency department of 1 hospital, while describing other developments up to the present. The participants were instructed to use their knowledge of actual resources at Changhai Hospital. The instructor announced the beginning and the end of the exercise and introduced the first problem, along with subsequent pacing messages, to the participants. The instructors presented the messages 1 at a time to individual participants. The group then discussed the issues raised by the message. The group determined what, if any, additional information was needed and requested that information. They took some actions with the teaching props provided to them. In addition, the participants received messages presented by the instructor individually, thus, making decisions for the team. At the end of each stage, the instructor invited the students to give a group report. At the end of the class, the instructor organized a debriefing, and each student was invited to share his or her feelings and questions. The TTX lasted for 3 hours, and the specific time allocation is shown in Table 1.

Table 1. Time allocation of the TTX

Data analysis

Data analysis was performed using SPSS 26.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics (M, SD) were calculated. The demographic characteristics and the participants’ evaluations were summarized using frequencies, percentages, means, standard deviations, medians, and quartiles. Multivariate stepwise regression analysis was used to examine the influences of the instructional props, the participants’ ratings of the difficulty of the training course, the participants’ degree of involvement, and the participants’ EPSS scores and SDS scores regarding perceptions of the TTX training course. All statistical tests were 2-tailed, and the level of statistical significance was set at P < 0.05.