The design of healthcare facilities is an inherently complicated process involving interdisciplinary teamwork among healthcare administrators, planners, programmers, designers, clinicians, and patient representatives, and others who have different backgrounds and professional languages. Communication between stakeholders during the facility design process, especially while using evidence to inform design and creating evidence by empirically evaluating the built environment, becomes difficult due to a lack of common understanding of terms and measures.

There is a need for a set of standard definitions of key terms and measures used in healthcare design—this base knowledge would make it easier to communicate with team members, interpret and translate research studies to design knowledge, generalize studies to different types of settings, compare data across multiple facilities, and develop a central repository of evidence.

In October 2009, The Center for Health Design (CHD) initiated a project to develop a standard glossary for evidence-based design (EBD) in healthcare. The first phase of the project aimed at: (1) identifying environmental variables and outcome measures in the existing EBD research; and (2) examining how these variables and outcomes were defined and measured in seven high-priority topic areas:

  • Healthcare-associated infections (HAIs)
  • Medical errors
  • Patient falls
  • Patient satisfaction
  • Patient waiting
  • Staff efficiency
  • Staff satisfaction 

A better understanding of key variables, metrics, and measurement tools currently used in EBD research will provide a crucial foundation for future phases of this project by enabling CHD, as well as others, to develop more accurate definitions of terms and variables, to develop more powerful metrics and tools, and eventually to enhance the quality of EBD research and practice.

This paper provides a synopsis of the EBD glossary terms, metrics, and measurement tools extracted from the literature as well as the process of the first phase. Because of space limitation, only a very small sample of the results is presented here. The complete results, including a full research report, literature analysis tables, glossary tables, and conceptual frameworks are available at CHD’s website: For corresponding tables, please see attachments below.



The CHD research team worked together with experts from CHD’s Research Coalition to conduct an extensive literature search and review. The literature review focused on peer-reviewed research articles that empirically demonstrated the effects of environmental variables on healthcare outcomes in each of the seven topic areas. The relevant articles from CHD’s previous literature reviews (for example, two comprehensive literature reviews by Roger Ulrich and colleagues [2004, 2008]) were retrieved.

Publications after CHD’s previous literature reviews were searched in research databases such as PubMed and EBSCO. Additional articles came from the reference lists of existing articles and the recommendations of academic and industry experts.

The articles were sorted and sifted for detailed literature analysis with the goal of creating a comprehensive list of variables as well as metrics and measurement tools. The purpose of the literature review was not to exhaustively review all articles on a particular subject. Rather, the goal was to review a sample of articles in different topic areas that had an empirical focus and clearly defined environmental and outcome variables. Each selected article was analyzed to extract relevant information, including the environmental variable(s) and outcome(s), metrics, measurement tools, sample(s), setting(s), research design, and findings. The results of the literature analysis included a series of tables and a chart for each topic area:

  • An article analysis table including the extracted information from each individual article together with the reference information;
  • A matrix showing the co-relationships between environmental variables and outcomes in a table format;
  • A model/conceptual framework depicting the relationships between environmental variables, intermediate environmental quality variables, and outcome variables; and
  • A glossary table synthesizing all variables (including their definitions), metrics, and measurement tools used in the studies reviewed. 

Finally, the seven glossary tables for individual topic areas were combined into one glossary table of healthcare environmental variables and one glossary table of healthcare outcome variables.



A total of 50 environmental variables and 35 outcomes were identified (shown in alphabetical order in Table 1) in the seven topic areas. Certain environmental variables may be associated with multiple outcomes in various topic areas. For example, the environmental variable “interior finish material” (e.g., carpet flooring versus vinyl) was related to both the “bacterial growth” on interior surfaces (an outcome measure in the topic area of HAIs) and the risk of “fall-related injuries” (an outcome measure in the topic area of “patient falls”). The relationships between the variables are illustrated in the models/frameworks in the full report.

Environmental and outcome variables or terms (including relevant topic areas in the parentheses), the definition, metrics, and measurement tools are included in the glossary tables in the full report (available at CHD’s website), of which only a small portion is shown in Table 2 and Table 3 (See attachments at bottom of page).


Environmental variables, metrics, and measurement tools

The environmental variables were typically measured on a categorical scale. In other words, many studies examined the outcomes under different environmental conditions, such as decentralized versus centralized nurses’ stations, or alcohol-based hand rub dispensers versus water/soap sinks. However, a great challenge in EBD research and practice is that some environmental variables or terms are not well defined in a quantifiable way. A variety of environmental conditions in different studies or study sites may bear the same name even though there are considerable differences between them.

For example, the term “decentralized nursing station” has been used to describe various unit configurations with more than one nurses’ station per unit, ranging from two to 11 patient beds per nurses’ station in one study (Zborowsky, Bunker-Hellmich, Morelli, & O’Neill, 2010). This inconsistency or variation in using the same term in different study sites and publications poses threats to the validity as well as the generalizability of research.

Although some articles provided descriptions (including floor plans and photos) about the study conditions, it is still probable that certain readers may overgeneralize the findings while ignoring the significant variations underlying the same name.

A relatively smaller number of environmental variables were measured on an interval/ratio scale where the distance between values indicates how different they are. For example, ventilation rate was measured by air changes per hour or cubic feet per minute, and one metric of the relative number of handwashing devices was the bed-to-sink/dispenser ratio.

In most studies, environmental variabl
es were manipulated by designers or researchers as independent variables. Other studies measured the environmental variables by using a variety of methods, including subjective measures, such as ratings of physical environment attractiveness; and objective measures using technological methods, such as photometer measurement of illumination level and tracer gas concentration decay technique for the calculation of ventilation rate.


Outcome variables, metrics, and measurement tools

Compared to environmental variables, healthcare outcome variables were relatively better defined with more standardized metrics and measurement tools. However, it is not uncommon to find controversies and weaknesses in the definition and measurement of key outcome variables. For example, there is not a universally accepted definition of patient falls.

Further, most studies in patient falls relied on incident reports completed by staff members to determine the rate of patient falls and other related outcomes. The practice of incident reporting varied significantly across different studies and hospitals, and was believed to underestimate the actual rate of falls.

Almost all outcome variables were measured on an interval/ratio scale. Metrics of patient safety outcomes typically included the prevalence of safety incidents (e.g., the number of infections or patient falls per 1,000 patient days) and the severity of consequences (e.g., the severity levels of medication errors: 1— little or no effect on patient; to 5—likely to lead to death). These outcomes were often collected through reviewing incident reports and medical records except for medication errors, which were often measured by directly observing and evaluating medication processes.

One large group of outcomes, including patient and staff satisfaction, stress, perceived patient waiting, staff burnout, and staff turnover intent, were subjective ratings collected by questionnaire surveys. Direct observation was a key method of measuring behaviors of patients and staff, such as handwashing compliance.

Several outcomes (e.g., surface contamination, staff travel, and staff stress) lend themselves to technological measurement methods, including electrocardiography monitoring, saliva sampling, and radioimmunoassay analysis, air sampling using biocollector, biology analysis, and indoor positioning system. Computer simulation is a major method in evaluating behaviors and performance of surgeons and pharmacists.


Conclusions and next steps

Rome was not built in a day. As a critical step toward a standard EBD glossary, this first phase work not only generated essential and useful resources for healthcare design and research but also identified the current status, including strengths, weaknesses, and gaps in the term definitions, metrics, and measurement tools. The future phases of this project also will rely on the contributions by interested, multidisciplinary volunteers from the field to glossary revisions and additions.

One critical component of the glossary development is to obtain input, feedback, and recommendations from key stakeholders through online and face-to-face discussion (including the online interface at CHD’s website and the two roundtable sessions at HEALTHCARE DESIGN conferences in 2010 and 2011). Further, additional topic areas (such as staff injuries) and additional sources of environmental terms and healthcare outcome measures, will be examined with help from academic institutions and others. With the growth of research in the field, the list of environment variables and outcome measures would be updated and expanded regularly. HCD


The authors would like to thank The CHD Research Coalition for its support. The Research Coalition nurtures, supports, and produces evidence-based design research that contributes to therapeutic, safe, efficient, and effective healthcare settings. Comprised of research professionals, design practitioners, and healthcare administrators, the Research Coalition steers CHD funding for healthcare design research, helps guide these projects to success, and develops information and tools for implementing evidence-based design in existing and new facilities. More information about the Research Coalition can be found at: