Table 3 Design features, decisions, and rationale
| Design feature | Final design decision | Rationale [Source]* |
|---|---|---|
| Blood pressure plot | ||
| Style of plot | Use a line graph | Unnecessary to introduce a novel design. Use a format with which all users are already familiar. [RT] |
| Denoting specific sources of BP readings | Use two symbols to denote BP data as “home” or “office” readings |
Unique symbols for additional possible data sources—beyond home and office measurements—could lead to confusion. [RT] Physicians reported specific differentiation beyond home and office measurements was unnecessary as some sources are already evident due to their density (e.g., high density inpatient or operative values). [FG] |
| 2-line paradigm (systolic and diastolic), mixing both home and office readings, with the source differentiated by two symbols | 4-line paradigm could result in overlap and visual confusion. [RT] | |
| Goal ranges | Add filled goal range bands on the graphical display to denote systolic and diastolic goal ranges | Allows of the visual centres of the brain to employ the pre-attentive attributes of color and 2-dimentsional position to judge control at a glance [16]. [RT] |
| Create goal ranges which are adjustable on a per patient basis | Goal ranges can vary for special populations or for patients with specific symptoms. [FG] | |
| Out of range | No additional affordances aside from data points being outside the goal range bands | Additional affordances, such as colored points or fills, were found to be distracting or unnecessary. [FG] |
| Color | Add colored goal range bands which match colored systolic and diastolic points and lines |
Strong patient preference for use of color. [FG] Creates a like-with-like paradigm for fast visual processing to determine if points are within or outside goal ranges [16]. [RT] |
| Use a two-color scheme of mint (#008471) for systolic BP measurements and cocoa (#9C652B) for diastolic measurements | Color scheme needs to be colorblind-safe and avoid conflict with existing color scheme in the EHR. [RT] | |
| Data and how to handle it | ||
| Data table | Include a data table to show the corresponding values for each point on the graphical display | Preferences of both patients and physicians for the inclusion of a data table with the measurement values. [FG] |
| Data density | Use a display which can accommodate 62 data points | A future with high density home BP measurements will require a display of sufficient size to aggregate and visualize the data. A proposal for data density was developed and presented in Table 2. [RT] |
| Missing data | Use a dashed line on the line graph when > 10% of consecutive data points are missing | The current potential for large amounts of missing data is high as home BP measurement is only beginning to become more common and missing data needs to be clearly denoted. [RT] |
| Smoothing data | Use a LOWESS algorithm to smooth data and add smoothing line to graphical display | Patients overweigh the impact of variability and outliers in their BP measurements [18, 19] while variability has been shown to have much less clinical significance, compared to mean BP [24]. [RT] |
| Annotations | Add an annotation timeline onto which use-generated annotations can be organized | The research team, patients, and physicians recognized the value of user-generated annotations for tracking behavioral changes impacting BP not easily captured elsewhere. [RT, FG] |
| Medication timeline | Incorporate a medication timeline so users can understand the impact of medication changes on BP measurements | The medication timeline we previously designed [25] can provide users with additional context which is currently unavailable. Patients found the timeline was intuitive to use and provided additional context to their BP measurements. [RT, FG] |
| Scrubber bar | Use a scrubber bar which links the various elements of the display | Patients found the scrubber bar helped link the various elements of the display (graphical display, data table, and medication timeline) into a more coherent story. [RT, FG] |