Table 3 Design features, decisions, and rationale

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]