BPMN SIX A BPMN 2.0 Surgical Intervention Extension

BPMN SIX A BPMN 2.0 Surgical Intervention Extension Concept and Design of a BPMN Extension for Intraoperative Workflow Modeling and Execution in the Integrated Operating Room Juliane Neumann, Max Rockstroh, Stefan Franke, Thomas Neumuth Leipzig University, ICCAS, Leipzig, Germany Juliane.Neumann@iccas.de Abstract. Modern integrated operating rooms (OR) become an enabling technology for new applications in workflow-driven surgical assistance. For this purpose, surgical activities and OR processes have to be described as Surgical Process Models (SPM). There have been approaches for modeling surgical workflows by using common business process modeling languages, like BPMN 2.0. However, BPMN is a general purpose modeling language, which lacks in representation of domain-specific concepts. The goal of this work is to provide a concept and design for a domain-specific extension of the BPMN modeling language for intraoperative surgical workflow modeling and execution in the integrated OR. Keywords: Surgical Workflow Modeling, Workflow Management, Business Process Modeling, BPMN 2.0 Extension, Integrated OR 1 Introduction Surgical workflow management provides process automation, optimization and analysis and is a prerequisite for computer-aided surgical assistance, situation-awareness and decision support in modern integrated operating rooms. Integrated ORs enable a vendor-independent safe and dynamic networking with open and interoperable device integration based on a plug-and-play functionality [1]. This subject has been addressed in the German flagship project OR.NET with more than 50 partners form academia and industry involved [2, 3]. Among others a service-oriented architecture (SOA) is used by medical devices for sharing their data and functionalities as services within the network [2]. Currently, the interoperability of medical devices and IT systems in the OR becomes an enabling technology for computer-aided assistance functionalities and new applications for surgical workflow tracking and modeling [4]. The information about the current situation and surgical events must be provided to the medical devices in the OR for situation-aware configuration and combination of supportive services [5,6]. For this purpose, the intraoperative processes, surgical activities and medical device actions

need to be abstracted, described and visualized as Surgical Process Models (SPMs) [5]. Neumuth et al. defined a SPM as a simplified pattern of a Surgical Process (SP) that reflects a predefined subset of interest of the SP in a formal or semi-formal representation [7, 8]. When modeling surgical processes and workflows, different aspects of a surgical intervention have to be taken into account. A 5-tupel for representing a complete surgical activity was proposed in [9], containing the surgical action, the actuator and the body part the actuator performed the action with, the used instruments/resources and the treated anatomical structure. In literature, different approaches for surgical process and workflow modeling have been described. The methods range from formal knowledge-based approaches using ontologies [10, 11], simple XML [12] or UML representation [6] to statistical methods, like Hidden Markov Models [13]. In addition, there have been attempts to model surgical workflows by using common business process modeling languages, like EPC, BPMN or YAWL [14, 15]. It could be shown, that especially BPMN is suitable for modeling surgical procedures due to its modeling abilities in different points of view and its process automation capabilities [14]. In contrast to other modeling languages, BPMN has a widespread distribution in academia and industry and a large tool support. BPMN 2.0 is declared as a ISO/IEC standard (19510:2013) for modeling and executing business processes [16]. However, BPMN is a general purpose modeling language, which lacks in modeling domain-specific concepts of surgical workflows, like the representation of surgical activities, anatomical structures or medical devices and clinical IT systems. Nevertheless, BPMN provides mechanisms for domain-specific language extension, which allow the extension by addition of domain-specific concepts [17, 18]. There are various extensions available in the area of healthcare processes, especially for clinical pathways (e.g. [19, 20]). In the topic of surgical process modeling using BPMN, research is sparse in general [21] and lacks completely in the domain of intraoperative surgical process modeling in respect to the special requirements of the application in the integrated OR. The goal of this work is to provide a concept and design for a domain-specific extension of the BPMN modeling language for intraoperative surgical workflow modeling and execution in the integrated OR. Therefore, various requirements emerging from the field of surgical workflow modeling and its extension to medical device interoperability will be defined and implemented in a BPMN Surgical Intervention Extension (BPMN SIX ). 2 Methods There are two major challenges in the development of BPMN extensions. First there are no official methodological guidelines for creating extensions and second there are no possibilities for generating graphical notations for extension concepts [17]. Hence, Stroppi et al. present a method for BPMN extension development [17], which was extended in respect to domain analysis and applied for clinical pathways by Braun et al. [22]. This extended method was used for the development of BPMN SIX and is described in the following section [22].

The method consists of six steps. First a requirements analysis based on a domainspecific use case or literature review should be performed in order to define the according domain requirements. Thereby different modeling languages have to be analyzed in respect to their applicability to the modeling domain and the intended use case. If the decision is made for BPMN, a domain-ontology has to be created. The described elements of the ontology have to be examined regarding their matching to BPMN elements. In the third step an equivalence check is performed. The check aims on the identification of BPMN extension elements and their extension requirements. Step 4 and 5 refers to the method of Stroppi et al. [17] and were used to create a valid BPMN extension model (CDME Conceptual Domain Model of the Extension) with an abstract syntax. In the sixth step the concrete syntax is implemented and graphical notations have to be defined for the extension elements. The approach of Stroppi proposes further steps, which allow the transformation of the BPMN extension model into an XML Schema Extension Definition Model and XML Schema Extension Definition Document. These steps are not included in this article but will be part of further research. The transformation of surgical workflow models in executable workflow instances is a prerequisite for the interoperable application of workflow management systems in the integrated OR. 3 Requirement Analysis 3.1 Domain Requirements Analysis The performed requirement analysis consists of three parts. The first part includes a literature review, which has been realized for surgical process and workflow modeling in [14]. Requirements that could not or just partly be fulfilled with BPMN were extracted for further analysis regarding the necessity for representation in BPMN SIX. In the second part, a use-case-based analysis was performed for the acquisition of requirements in the domain of integrated ORs as well as medical device and systems interoperability. In the third part, established BPMN extensions for healthcare and clinical pathways were considered for the combination of extension elements with BPMN SIX due to the hypothesis that processes in the healthcare domain have several commonalities. For this purpose, BPMN4CP (BPMN for Clinical pathways version 1.0 [19] and 2.0 [23]) was chosen as an example. 3.2 Decision of Modeling Language and Domain Ontology Based on the performed requirement analysis in [14] and in comparison with EPC and YAWL, BPMN was chosen as appropriate modeling language for surgical workflow modeling. In the next step, the requirements were translated in domain-specific concepts and modeled as a domain ontology, which is depicted in Fig 1. Surgical Activities are the central concept in surgical process modeling and the smallest logical units of a surgical process. They are described as 5-Tupel consisting of the Actuator and the Used Body Part, the Surgical Action, the Anatomical Structure and the used Resource or Instrument (e.g. surgeon uses right hand to cut skin with scalpel). In accordance to [19],

the surgical activity can be specified as Diagnosis Task, Treatment Task and Supportive Task. According to MacKenzie et al. [24] the Surgical Step describes a lower granularity level of the surgical process. Therefore, a surgical step consists of several surgical activities, gateways, events and sequence flows. A Surgical Phase is composed of several surgical steps. The lowest granularity level is the surgical Intervention, which is composed of several phases (Fig. 1). A Process Flow organizes and arranges all activities within the pathway that are necessary for the appropriate treatment of the patient. [19]. The concept Parallel Flow covers the parallel and simultaneous execution of activities [19]. In addition, a concept for Exceptional Treatment covers the Treatment of complications or other kinds of irregularities (predictable and unpredictable) [19]. If predictable and unpredictable exceptions occur due to resource unavailability, the corresponding Resource Exception concept is needed. Fig. 1. Domain Ontology for intraoperative processes in the integrated OR. Elements marked with *, were extracted from BPMN4CP [19], [23] In the revised version of BPMN4CP a new Resource view for BPMN process models has been proposed [23]. Like clinical pathways, surgical processes consume or use a huge variety of resources during process execution. Hence, it is necessary to define a specific resource representation in the surgical process model. Braun et al. defined a Resource as any consumable or usable object that is necessary for the fulfillment of (CP) activities. Resources can be assigned and composed to Resource Bundles. [23]. For surgical process modeling, resources like surgical instruments, medical devices, materials and substances should be describable. On the technical site clinical ITsystems, different types of clinical data and documents have to be defined as well. Therefore, the complete Document concept of Braun et al., which contains Case Charts, Clinical Documents, Unstructured Documents (images, videos, text documents or signaling documents) as well as Structured Documents, has been adapted for surgical process modeling [23].

3.3 Equivalence Check Table 1 shows the equivalence check results of the domain-specific elements for surgical process modeling. The concepts were classified into one of three equivalence groups [19]: Equivalence, when there is a semantically equivalent construct in the BPMN. Conditional Equivalence, when there is no obvious semantic matching with standard elements, but rather situational discussion is necessary. No Equivalence, when there is no equivalence to any standard element. After the classification, a CDME model concept is created. The decision for mapping the surgical process concepts to a BPMN element respectively to a BPMN4CP concept or create an specific BPMN SIX extension concept is made on base of the adaption of different translation rules proposed by Stroppi et al. [17]. 4 and Design 4.1 Domain Modeling Based on the equivalence check a CDME UML class diagram (Fig. 2) was modeled. The different granularity levels were represented in the BPMN SIX CDME by using Surgical Task as instantiation of BPMN Activities. Surgical Steps, Phase and Intervention are instantiations of BPMN Sub-process concepts. When representing different granularity levels, BPMN SIX can be used for bottom-up modeling of low level surgical tasks and top-down modeling of high granular surgical tasks as well as surgical phases. A surgical activity combines the surgical action, the actuator and the used body part, the treated anatomical structure and the used resource (instrument or medical device) [7]. The action concept is modeled as parameter for the surgical activity without a graphical notation. The anatomical structure is represented with a new graphical notation and can be added to a surgical activity with a resource relation [23]. The resource view proposed by Braun et al. [23] was adapted for surgical workflow modeling. Materials, substances and other accessories could be represented with consumption resources, medicine or auxiliaries. These resource concepts were extended by specific concepts for surgical instruments, medical devices and clinical IT-systems. Due to their importance in surgical process modeling as well as their unspecific representation in BPMN4CP, a graphical notation was developed. The integration of device information in the surgical process model is a prerequisite for situation-aware assistance functionalities. Therefore, the information of the actual surgical situation has to be provided and exchanged between workflow management, OR devices and clinical systems. Hence, Franke et al. proposed requirements for this integration [5]: Independence of process model and OR integration. The representation of medical devices in the integrated OR is described in the newly developed extension of the IEEE 11073 standards family (11073-10207 Domain Information & Service Model) as Medical Device Information Base (MDIB) [1]. The

Table 1. Equivalence Check of requirements (referred to [22]) Concept Semantics Equivalence Check CDME Process Perspective Surgical Activity Surgical activities are the smallest logical units of a surgical process, which can be specified as Diagnosis Task, Treatment Task and Supportive Task. Surgical Step Surgical step consists of surgical activities, gateways, events and sequence flows and has a lower granularity level than surgical activities. Equivalence Task, Activity [18], Diagnosis Task, Treatment Task, Supportive Task [19] BPMN Concept, BPMN4CP Concept, Equivalence Sub-process [18] BPMN Concept, Phase A surgical phase is composed of several surgical steps. Equivalence Sub-process [18] BPMN Concept, Intervention The lowest granularity level is the surgical intervention, which is composed of several phases. Action The action is part of the surgical activity and describes the physical actions performed by the surgeon. Equivalence Sub-process [18] BPMN Concept, No Equivalence Parallel Flow Parallel and simultaneous execution of activities [19]. Equivalence Parallel Flow [19] BPMN4CP Concept Equivalence Exceptional Treatment [19] BPMN4CP Concept Exceptional Treatment Treatment of complications or other kinds of irregularities (predictable and unpredictable) [19] Resource exception Treatment of predictable and unpredictable exceptions in respect to resource integration (e.g. resource unavailability due to errors) and their influence on the surgical process. Organizational Perspective Equivalence Event Sub-process, Error Events, Compensation Events [18] BPMN Concept, Actuator Persons involved in an intervention Equivalence Pool [18] are used to model roles, organizational units, systems or departments. Used Body Part Body part used by the actuator during a surgical activity (e.g. right hand, left hand). Resource Perspective Resource Definition of different intraoperative Resources, which are used during surgical activity, e.g. instruments, medical devices, materials. Resource Bundle Orchestration of different intraoperative resource elements (e.g. instrument sets). Resource Orchestration The resource orchestration modeles the combination of medical device services. Anatomical Structure The treated anatomical or pathological structure during a surgical activity. Surgical Instruments and Materials Specification and classification of surgical instruments and consumables. Medical Device Specification and classification of medical devices. The structure and necessary elements as well as the state of Medical devices have to be described in form of a standard-compliant Medical Device Information Base (MDIB) [1]. Clinical IT system Specification of medical information system structure and functionalities (e.g. PACS, CIS). Clinical Documents and Data Specification of documents for medical or administrative purpose [23] BPMN Concept, Equivalence Lane are sub-partitions within a Pool [18] BPMN Concept, Equivalence Resource [18, 23] BPMN Concept, BPMN4CP Concept Equivalence Resource Bundle [23] BPMN Concept, BPMN4CP Concept No Equivalence. No equivalence. Conditional Equivalence (by specification) Resource [18]. There is no appropriate resource concept for the representation of surgical instruments and materials. The extension of BPMN4CP resource concepts is possible [23]. No Equivalence. There is no appropriate resource concept for the representation of medical device functions, states and structure. No Equivalence. The BPMN Lane concept is not an adequate representation for the diversity of clinical IT systems their function and their structure. Equivalence Clinical Document [19, 23] BPMN4CP Concept MDIB consists of two parts. The first part is the Medical Device Description, which defines the device capabilities in a tree structure with their Virtual Medical Device

components (VMD), channels and metrics. The second part describes the Medical Device State for each description. In BPMN SIX the MDIB is linked to the medical device representation, which is defined in the CDME. Therefore, the modeling of processes and medical devices should be independent from each other. Orchestration of functionalities and medical device services. The abstract functionalities of different medical devices need to be described, combined and orchestrated for situation-aware assistance. Therefore, the needed device services and functionalities of clinical IT systems have to be modeled and configured as MDIB-subtrees. Then these subtrees could be combined by the resource orchestration concept of the developed CDME. Late binding of process information to concrete devices. Late binding is needed to preserve the plug-and-play functionalities in the integrated OR. The modeled functionalities were mapped to concrete devices in the current OR configuration during runtime. Therefore, a tree-mapping between the modeled MDIB subtrees and the specific MDIB of the medical device configuration in the OR has to be performed. 4.2 Abstract Syntax and Concrete Syntax The CDME model was translated in a valid BPMN extension model. In Fig. 2 a part of the abstract syntax of BPMN SIX is depicted. Fig. 2. Example part of the CDME abstract syntax

The classes depicted in grey are BPMN original concepts with their according relations, which are defined in [18]. In contrast to the generalization of concepts (e.g. Task is a generalized concept of Diagnosis Task) an instantiation of concepts defines the specific realization of a concept (e.g. Surgical Activity is an instance of Task). The resource domain model was extended by medical devices, clinical IT systems, anatomical structures, materials and instruments. The BPMN4CP concept Equipment stands for all medical-related material [23] and is described in more detail by the concept of surgical instruments (e.g. scalpel or a surgical drill). A Consumption Resource describe resources, which are consumed within patient treatment [23] and is concretized by the concept of materials (e.g. dressing or drainage). Auxiliaries refer to all other resources, which are not primarily intended for treatment but needed for equipment, rooms or machines [23] (e.g. CO 2 gas for insufflation). Medical devices like a suction device or a microscope could be modeled by capability and current state description in a MDIB subtree with the presented parameters. In Fig. 3 the concrete syntax with the extension of graphical notation is presented. The resource view is adapted from BPMN4CP. Concepts for Instruments, Medical Devices, Clinical IT Systems, Resource Orchestration and Anatomical Structure are part of the BPMN SIX extension concept. Fig. 3. Concrete Syntax of BPMN4CP [23] and BPMN SIX Extension 5 Discussion and Conclusion In this work, a domain-specific extension of the BPMN modeling language for intraoperative surgical workflow modeling and execution in the integrated OR is described. The defined requirements and the developed CDME model can be regarded as a first draft for an incremental development of the BPMN SIX extension. The integrated OR is a variable, complex and changing environment, thus a continuously occurrence of new requirements could be expected. In addition, the observer-based acquisition of Surgical Processes [12] may be replaced by automatic workflow recording based on medical device signal data, video and image data (e.g. from surgical microscope or endoscope), sensor data, instrument or gesture recognition, in the near future. The research in the domain of workflow recognition is manifold and promising in respect to automatic acquisition of Surgical Process Models. These developments will require to change existing concepts and add new ones to the BPMN SIX extension model continuously.

Another unsolved issue is the acquisition and formalized representation of surgical needs and their corresponding assistance functionalities, e.g. the situation-aware profiling for different surgeons. Currently, the surgical situation can be characterized, but the implications to the needed situation-aware assistance are missing. Therefore, rule-sets (e.g. by using the BPMN compatible Decision Model Notation ((DMN) [25]) have to be implemented and combined with the process model and the medical device model. Thus, the orchestration of medical device basic services could lead to new opportunities in situation-aware surgical assistance, decision support and information management. In the next step BPMN SIX will be implemented and extended for workflow execution. Afterwards an approval and evaluation will be performed. Acknowledgements. This work has been partially funded by the German Federal Ministry of Education and Research (BMBF) in the KMU-innovativ funding program under reference number 01IS14022D as part of the OntoMedRisk project (http://www.ontomedrisk.de). References 1. M. Kasparick, S. Schlichting, F. Golatowski, and D. Timmermann, New IEEE 11073 standards for interoperable, networked point-of-care Medical Devices, in 2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015, pp. 1721 1724. 2. F. Kühn and M. Leucker, OR.NET: Safe Interconnection of Medical Devices, in Foundations of Health Information Engineering and Systems, J. Gibbons and W. MacCaull, Eds. Springer Berlin Heidelberg, 2013, pp. 188 198. 3. OR.NET - Sichere dynamische Vernetzung in Operationsaal und Klinik. [Online]. Available: http://www.ornet.org/. [Accessed: 15-Jun-2016]. 4. S. Franke, M. Rockstroh, E. Schreiber, J. Neumann, and T. Neumuth, Context-aware medical assistance systems in integrated surgical environments, in Proc. of the 28th Conference of the international Society for Medical Innovation and Technology (SMIT), Delft, 2016. 5. S. Franke, P. Liebmann, and T. Neumuth, Connecting workflow management to the OR network: Design and evaluation of a bridge to enable dynamic systems behaviour, Biomed. Eng. Biomed. Tech., vol. 57, no. SI-1 Track-N, pp. 771 774, Sep. 2012. 6. T. Neumuth, P. Liebmann, P. Wiedemann, J. Meixensberger, and others, Surgical workflow management schemata for cataract procedures, Methods Inf Med, vol. 51, no. 5, pp. 371 382, 2012. 7. T. Neumuth, P. Jannin, G. Strauss, J. Meixensberger, and O. Burgert, Validation of Knowledge Acquisition for Surgical Process Models, J. Am. Med. Inform. Assoc., vol. 16, no. 1, pp. 72 80, Jan. 2009. 8. T. Neumuth, S. Schumann, G. Straub, P. Jannin, J. Meixensberger, A. Dietz, H. Lemke, and O. Burgert, Visualization Options for Surgical Workflows, Int. J. Comput. Assist. Radiol. Surg., vol. 1, no. 1, pp. 438 440, 2006. 9. T. Neumuth, G. Strauß, J. Meixensberger, H. U. Lemke, and O. Burgert, Acquisition of Process Descriptions from Surgical Interventions, in Database and Expert Systems Applications, S. Bressan, J. Küng, and R. Wagner, Eds. Springer Berlin Heidelberg, 2006, pp. 602 611.

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