Cross-recording Analysis in LabChart Lightning
- 25 Sep 20
LabChart Lightning has a flexible table, where you can analyse data from different recordings, all in one place. The table gives you the power to do cross-recording analysis without having to export your data.
In this video we’re going to analyse data from 11 recordings of non-invasive blood pressure (NIBP) in humans. To follow along, you can download the NIBP example data here.
In this example we will use data sampled during a wall sit exercise to calculate baroreflex sensitivity. We have a total of 11 recordings in this project, each representing a different subject.
Creating regions of interest
Lets start with the first of our recordings. There are 6 signals of sampled data, and today we’ll be working with Systolic Pressure and Inter-beat Interval, IBI for short. I’m going to drag the Inter-beat Interval signal up so that it’s in the same channel as Systolic Pressure. Now I’ll maximise this channel, so that we’re only looking at the data we are interested in.
Within the data, you should be able to see two annotations. These mark the start and end of the wall sit exercise. This is the data we want to analyse, so we'll create a wall sit region and a Baseline region.
How to create a region in LabChart Lightning »
A region is a saved selection of data in Chart View, which is used to mark and analyze data of interest. Regions have a start time, an end time, and a type; e.g. “Baseline”, “Occlusion”, and are used to calculate data in the Table View.
Displaying data in table view
When we open the Table View (using the button in the left sidebar), we can see data for the two regions we created above. The table shows that the mean systolic pressure is higher during the wall sit than during the baseline.
The table uses groups to categorise data. Checking the properties for this recording, we can see that this particular recordings is in the “Female” group, and the data is under the “Female” heading in the table. As we create more regions in our other 10 recordings, that data will be categorised too.
Now lets open our second recording, and follow the same steps as before, moving the Inter-beat Interval signal, and creating regions. You can see that the two regions are automatically added to the table, and we have started doing cross-recording analysis.
The table has automatically calculated the mean across our two different recordings. Continue to do this for the other 9 recordings, and you will see all the data appear in the table.
You can see that the subjects are now split into Female and Male groups, and the mean is calculated for each group.
To calculate baroreflex sensitivity, I need to know the change in systolic pressure and inter-beat interval, during the wall sit exercise. I can calculate this by adding more columns to the table. When I select End Value minus Start Value, you can see the data appear in the table.
Correcting for unwanted artefacts
We expect the change in interbeat-interval to be negative, but for subject two, we have a large, positive value. To investigate this anomaly, we can click the table cell, then navigate to the region that this data comes from in Chart View.
We can see that the data has a few unwanted artefacts at the start of the region. Let’s move the start of the region, so that this bad data isn’t included. You can see that the table has updated automatically, and is now showing a negative change in inter-beat interval for subject 2.
Calculating baroreflex sensitivity in Table View
Now that we have our relevant data in the table, we can calculate baroreflex sensitivity during the wall sit exercise. Open the table view properties and choose “Create Column” from the Calculated Columns dropdown. In this example we are going to label it BRS, for baroreflex sensitivity.
We can use the calculation editor to select data from the table. In this particular example, I'm going to calculate baroreflex sensitivity using the change in interbeat interval, divided by the change in systolic pressure.
You should now be able to see the baroreflex sensitivity for each subject, and the mean across our two groups.
You can add other cross-file calculations using the Table View Properties. These are called Summary Calculations.
Hiding data in Table View
As more data is added to the table, you may need more space. You can hide data you aren’t using to reduce clutter, and you can also close the chart view to create more space.
To hide data in Table View, click on the column you with to hide then navigate to the Table Regions Properties tab on the right. Under 'visible channels' you can select the channels you wish to hide.
In this example we have analyzed sampled data, but you can also create calculated signals and include them in your regions, so that they appear in the table for analysis.
The LabChart Team