2.2.2. System Form

The healthcare delivery system is composed of resources representing system form (i.e., the components of a system). Four types of resources have been previously defined in the literature [15], similarly to system function. The healthcare delivery system form is thus represented as the union of the following four resources: *Transformation Resource*: A resource capable of a transformative effect on its operand (e.g., the health state of an individual). They include the set union of *human* transformation resources (e.g., surgeon, cardiologist, psychologist) and technical transformation resources (e.g., operating theaters, drugs, chemotherapy infusion room, delivery room); *Decision Resource*: A resource capable of advising the operand, an individual, on how to proceed next with the healthcare delivery system. They include the set union of human decision resources (e.g., oncologist, general practitioner) and technical decision resources (e.g., decision support systems, electronic medical record decision tools); *Measurement Resource*: A resource capable of measuring the operand: here the health state of an individual. They include the set union of human measurement resources (e.g., MRI technician, sonographer, phlebotomist) and technical measurement resources (e.g., magnetic resonance imaging scanner, ultrasound machine, hematology analyzers); and *Transportation Resource*: A resource capable of transporting its operand: the individuals themselves. They include the set union of human transportation resources (e.g., runners, emergency medical technician, clinical care coordinator) and technical transportation resources (e.g., ambulance, gurney, wheelchair).

## 2.2.3. System Concept

The allocation of system function to form then allows for the composition of a matrix representing a bipartite graph between system processes and resources, which is referred to as the system concept. This allocated matrix is defined as the system knowledge base [56–62] and represents the elemental capabilities that exist within the system.

#### **3. Designing Clinical Models Using Systems Thinking and Systems Methodology: An Illustrative Example**

This section takes a current clinical model and develops it into a system model as an illustrative example of a clinical model represented using elements from systems thinking. The example is of a service model that embeds behavioral health (BH) care into primary care. The remainder of this section describes the clinical model, followed by the methodology for developing the system model, and finally presents a detailed description of the designed system model.

#### *3.1. Clinical Model of Behavioral Health Integration into Primary Care*

Behavioral health care is a broad umbrella term used to encompass care for patients around mental health, substance use conditions, health behavior change, life stresses and crises, as well as stress-related physical symptoms [63,64]. Growing recognition for behavioral health needs makes this example critical and timely. The National Academy of Medicine has highlighted the importance of health care's recognition of the interaction of physical, mental, and substance use issues when providing health care [65].

The importance of behavioral health has been echoed by many sources, including the World Health Organization (WHO) [66], the Agency for Healthcare Research and Quality (AHRQ) [67], and the Substance Abuse and Mental Health Services Administration (SAMHSA) [68]. The call to action has been strengthened by recent federal and state actions, including the Mental Health Parity and Addiction Equity Act of 2008 ensuring parity in coverage between behavioral and physical conditions and the Patient Protection and Affordable Care Act (ACA) of 2010 containing many provisions promoting integrated behavioral and physical care delivery.

There currently exist several clinical models that describe varying levels of integration of behavioral health into primary care. One of the typically referenced models is the Collaborative Care Model (CoCM) based on the IMPACT trial [69]. The Collaborative Care Model was developed by the University of Washington's Advancing Integrated Mental Health Solutions (AIMS) Center [70]. It is typically presented using the Collaborative Care team structure visual, published initially in 2015, Figure 1 [71], and updated in 2017 with a newer visual, Figure 2 [70]. CoCM includes several figures that describe certain aspects of the model, such as the stepped care aspect of the model (where a stepped intensity level of providers are enlisted if insufficient results are being achieved) [72], or the step-by-step guide to implementing the model (described as a one-page document of high level tasks) [73]. The closest representation of functions and activities is described by the task list in Figure 3.

**Figure 1.** Collaborative Care team structure from 2015 (adapted from works created by the University of Washington Advancing Integrated Mental Health Solutions Center, 2015, [71]).

**Figure 2.** Collaborative Care team structure from 2017 (adapted from works created by the University of Washington Advancing Integrated Mental Health Solutions Center, 2017, [70]).


**Figure 3.** Collaborative Care tasks (adapted from works created by the University of Washington Advancing Integrated Mental Health Solutions Center 2012, [74]).

While the CoCM is considered a clinically successful model, "the degree of integration of behavioral care into the primary care setting can vary from selective screening, diagnosis, brief treatment, and referral to a truly integrated care approach in which all aspects of primary care recognize both the physical and behavioral perspectives" [75]. This statement describes the dissociation between the description of the model and many varying levels of implementation across different healthcare delivery systems.

#### *3.2. Methodology for Developing the System Model*

A team at a local hospital was assembled and tasked with integrating behavioral health into primary care for an initial implementation at a test site, to be further rolled out in the future as a system-wide model to several other sites. The team included a systems engineering researcher and a range of personnel from the Departments of Psychiatry and Internal Medicine. The team proceeded to develop the hospital's integrated behavioral health service, with a heavy focus on the clinical aspect of the model followed by the operational aspect of the service model. This one-year implementation environment and process provided the knowledge needed for the development of the system model from an engineering perspective. Developing the system model of the CoCM was achieved in two steps: (1) by first describing system function, form, and context and (2) graphically representing the system.

First, the healthcare service model was described from a system function and form perspective by identifying the processes and resources, using the methodology presented in Section 2 and described in more detail in prior work [15]. Next, the system context was constructed, describing the resources

performing each function at several clinically appropriate levels. This included a high-level description of the model as is typically presented in healthcare and in other fields. Next, more specific levels describing the details of the operations were constructed. This was prepared so as to highlight specific pros of integration. The determination of resources, processes, and allocation of function to form at varying levels was accomplished in two ways and from two sources. First, the material and literature on the Collaborative Care Model was used to begin to develop the model. Next, the year-long experience shadowing, interviewing and meetinging at the implementing hospital provided the much needed details.

Second, the system model was represented using a systems engineering graphical language. As part of systems thinking and systems engineering, there exists a systems modeling language that maps English language structure into graphical elements [76]. It also involves a unique vocabulary for describing structure and function of a system and can therefore be thought of as a language. The model was graphed using the model-based systems engineering tool, SysML. Finally, the model was presented and validated through individual and group feedback from the hospital team integrating behavioral health into primary care.

#### *3.3. Description of the System Model*

This section describes the system model describing the integration of behavioral health into primary care based on the collaborative care model. The multi-level system model is described by three levels. The description of the model follows in the remainder of this section, organized by system function, form, and concept.
