In order to make comparisons between different vessels and experimental conditions, an internal circumference that exerts a Target Pressure needs to be determined to make comparisons meaningful. The relaxed vessel wall is stretched to a number of micrometer settings for a specific size myograph. The vessel wall force in response to each stretch is recorded by using the Add Point command. After a curve is generated from these forces, the Calculate command is used to determine the internal circumference at a Target Pressure, usually 13.3kPa. The normalized internal circumference is usually determined to be 90% of this value.
Calibrate the myograph(s) to be used in the experiment, according to procedures outlined in the myograph documentation.
With the wires positioned and exerting no stretch, click Record.
If the wires have been properly calibrated, the pressure should be zero. Click Stop.
In Two Cursor Mode, position the cursors on either side of a representative section of the trace and select Add Point from the Normalization menu. The mean value between the cursors will be recorded in the Normalization Dialog.
Increase the micrometer setting to stretch the vessel wall minimally. Click Record.
After the pressure has stabilized, click Stop.
Position the cursors on either side of a stabilized section of the trace and select Add Point from the Normalization menu.
Repeat this procedure for a number of micrometer settings. Once enough points have been recorded, select Calculate from the Normalization menu, opening the Normalization Dialog. The micrometer setting, the force registered by the wires, and the vessel wall pressure are displayed for each data point recorded.
In the Normalization Dialog, enter the Target Pressure, the Wire Diameter, the IC Ratio, and the Vessel Length.
Click Fit Exponential Equation to Data. A graph is generated and the Internal Circumference at the Target Pressure, the normalized IC, and the correct micrometer setting for that normalized internal circumference are displayed.
Outlying data points can be deleted by selecting the point and clicking Delete Point.