How can a physiological event's propagation velocity be calculated in LabChart?

Event propagation velocity relates to how fast an event such as a blood pressure pulse or a nerve action potential propigates down an artery or a nerve fiber.  Many analysis menthods are possible utilizing the many features in LabChart. Using the simple method described below, LabChart can calculate the velocity of such events with ease provided the following criteria are met:

  1. The event is being recorded with two transducers or electrodes at different points alont the event's path of propagation.
  2. The output of these two transducers or electrodes are being recorded into separate channels in LabChart.
  3. The distance between these two transducers or electrodes is known.

With these criteria met, the Find Feature and Data Pad can be used to find the event's propagation velocity. Please reference the example file located HERE while reviewing the process outlined below. This file has the output for two pressure transducers being recorded on Channels 1 and 2 of the file respectively.  For the purpose of this example, pressure transducer 1 is 1 centimeter up stream pressure transducer 2 in the artery.

The first step is to setup the Data Pad in LabChart.  The following Data Pad columns will be required:

A selection duration column.

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And a formulae column with the following formula input.

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To enter formulae into a Data Pad cell you will need to left mouse click the cell edit mode button.

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Left mouse click the cell in the first row of the column, and enter the desired formula by using the editing bar at the top of the Data Pad window.

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You can also name the column you entered the formula into by right mouse clicking the column title block, and selecting the "Rename Column..." option form the drop down menu that appears.

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The Data Pad will appear as follows when setup correctly for the example data.

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The Data Pad can now be populated with the Find Feature.  The Find Feature can be accessed under the LabChart Command menu by selecting the "Find..." option. 

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In the Find and Select settings window that appears, direct LabChart to move the active point to the beginning of the file.

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Open the Find and Select settings window again, and direct LabChart find the local maxima in Channel 1 and move the active point to it.

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Open the Find and Select settings window one more time, and direct LabChart to move forward, find the local maxima in Channel 2, and select to the previous point.

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In the example file, the following selection will be made.

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You can now add this selection duration to the Data Pad by selecting the "Add to Data Pad" option from the LabChart Commands menu.

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The Data Pad will now contain the selection duration and the calculated propagation velocity.

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The process outlined above can be repeated multiple time through the file, and can also be automated with a LabChart Macro.  For more information about how to record/write a Macro in LabChart, please review the Macro help topic in the LabChart Help menu.