Unveiling Blood Pressure Dips: Exploring Insights with Radial Bar Charts in Power BI

Blood pressure dips, often referred to as the "dip," signify a decrease in blood pressure levels, particularly during nighttime compared to daytime. Understanding these dips is crucial for assessing cardiovascular health.

Understanding Blood Pressure Dips

Before we dive into visualizing blood pressure dips with radial bar charts, let's briefly discuss what blood pressure dips are and why they matter.

Blood Pressure: Blood pressure is the force exerted by circulating blood against the walls of blood vessels. It is typically measured in millimeters of mercury (mmHg) and consists of two values: systolic pressure (the pressure when the heart beats) and diastolic pressure (the pressure when the heart rests between beats)

Blood Pressure Dips: Blood pressure dips refer to temporary decreases in blood pressure, often occurring during periods of relaxation or sleep. While some degree of blood pressure dipping is normal, excessively low blood pressure can indicate underlying health issues such as dehydration, heart problems, or medication side effects.

Dipping status is further categorized into 4 dipping patterns

Dippers: A Sign of Healthy Circadian Rhythm

Dippers exhibit a normal decrease in nighttime blood pressure, reflecting a healthy circadian rhythm.

Non-Dippers: Elevated Cardiovascular Risk

Non-dippers experience relatively unchanged blood pressure levels during nighttime compared to daytime, indicating increased cardiovascular risk.

Extreme Dippers: Vigilance Required

Extreme dippers demonstrate a more pronounced reduction in nighttime blood pressure, requiring careful monitoring to prevent potential complications such as hypotension.

Reverse Dippers: Abnormal Pattern, Elevated Risk

Reverse dippers witness an increase in blood pressure during nighttime, contrary to the expected decrease, suggesting higher cardiovascular risk.

Range	Category
< 0 %	Reverse Dipper
0%-10%	Non-Dipper
10%-20%	Dipper
>20%	Extreme-Dipper

Visualizing Blood Pressure Dips with Radial Bar Charts

Before delving into the intricacies of blood pressure patterns, let's first familiarize ourselves with the dataset we'll be working with. In this dataset, which comprises 77 distinct patients, we have identified the following distribution among the blood pressure dip categories:

• Non-Dippers: 49 patients

• Dippers: 4 patients

• Extreme Dippers: 5 patients

• Reverse Dippers: 7 patients

Now that we clearly understand the dataset and the distribution among different blood pressure dip categories, let's explore how to visualize this data using a radial bar chart.

Creating a Radial Bar Chart

First, we created a DAX function to specify BP Dip categories as per the given ranges

Dip Category = 
IF(
    ('Blood Pressure Tests'[24Hour-SBPDIP%]>= 0 || 'Blood Pressure Tests'[24Hour-DBPDIP%]>= 0) && ('Blood Pressure Tests'[24Hour-SBPDIP%] < 10 || 'Blood Pressure Tests'[24Hour-DBPDIP%] < 10) , "Non-dipper",
 IF(
        'Blood Pressure Tests'[24Hour-SBPDIP%] >= 20 ||'Blood Pressure Tests'[24Hour-DBPDIP%] >= 20, "Extreme Dipper",
        IF(
            ('Blood Pressure Tests'[24Hour-SBPDIP%] >= 10 || 'Blood Pressure Tests'[24Hour-DBPDIP%] >= 10) && ('Blood Pressure Tests'[24Hour-SBPDIP%] < 20 || 'Blood Pressure Tests'[24Hour-DBPDIP%] < 20), "Dipper",
            IF(
                'Blood Pressure Tests'[24Hour-SBPDIP%] < 0 || 'Blood Pressure Tests'[24Hour-DBPDIP%] < 0, "Reverse Dipper",
            BLANK()
        )
    )
))

To kickstart our custom visualization journey, we'll begin by creating a foundational Donut chart in Power BI. This Donut chart will serve as the basis for our eventual radial chart, allowing us to visualize the distribution of patients among different blood pressure dip categories.

Step-by-Step Guide:

1. Select Donut Chart Visualization: In Power BI Desktop, navigate to the "Visualizations" pane and select the Donut Chart Visualization option.

2. Assign Data to Visual Elements:

• Drag and drop the count of patients (Patient ID) to the "Values" field of the Donut chart.

• Drag the blood pressure dip categories (Dip categories) to the "Details" field of the Donut chart.

3. Customize Visual Appearance:

• Turn off the detail labels and legends to declutter the visualization and focus solely on the distribution of patients among different blood pressure dip categories.

• Increase the inner radius of the Donut chart to 85% to create a wider center hole, enhancing the visual appeal and emphasizing the categories. Apply color formatting for Non-Dipper category:

• In the Filter Pane, under the Dip category, choose only  "Non-Dipper" and "Extreme-Dipper"

• For the "Non-Dipper" category, choose a distinct color to highlight its significance. You may opt for a vibrant color that stands out.

• For the "Extreme-Dipper" category, match the colors to the background color of the slide to maintain consistency.

Apply color formatting for "Reverse-Dipper" category:

• Duplicate the "Non-Dipper" category radial bar chart and Under the Dip category, choose only "Extreme-Dipper" and "Reverse-Dipper".

• For the "Reverse-Dipper" category, choose a distinct color to highlight its significance.

• For the "Extreme-Dipper" category, match the colors to the background color of the slide to maintain consistency.

Apply color formatting for "Extreme-Dipper" category:

• Duplicate the "Reverse-Dipper" category radial bar chart and Under the Dip category, choose only "Extreme-Dipper" and "Reverse-Dipper".

• For the "Extreme-Dipper" category, choose a distinct color to highlight its significance.

• For the "Reverse-Dipper" category, match the colors to the background color of the slide to maintain consistency.

• Adjust the Rotation to 205 degrees to ensure that the radial bars are symmetrical and aligned with other radial bars.
  

Apply color formatting for the "Dipper" category:

• Duplicate the "Reverse-Dipper" category radial bar chart and Under the Dip category, choose "Dipper", "Reverse-Dipper" and "Extreme-Dipper".

• For the "Dipper" category, choose a distinct color to highlight its significance.

• For the "Extreme-Dipper" and "Reverse-Dipper" categories, match the colors to the background color of the slide to maintain consistency.

• Adjust the Rotation to 254 degrees to ensure that the radial bars are symmetrical and aligned with other radial bars

4. Stacking Radial Charts:

• Turn off the background for all the charts to ensure the visibility of all the radial bars after stacking

• Stack the radial charts one by one, starting with the Reverse-Dipper chart placed on top of the Non-Dipper chart. Ensure proper alignment to maintain visual consistency.
  

• Place the Extreme-Dipper chart on top of the Reverse-Dipper chart and align it properly.

• Finally, place the Dipper chart on top of the Extreme-Dipper chart and align it to complete the stacking process.

5. Grouping of charts:

• Select all the charts together and group them to show as a single chart

By following these steps and applying the specified adjustments, we'll create a visually striking radial chart that effectively communicates the distribution of patients among different blood pressure dip categories. This serves as a comprehensive visualization of our data, allowing for in-depth analysis and insights.