The Volume Calibration for the MPVS Large animal system can be carried out in the MPVS control software using Rho Cuvette and Baan’s equation. This is performed before recording but requires previous determination of alpha.The Rho Cuvette calibration should be conducted following the selection of your catheter in the catheter tab.
To carry out a Rho Cuvette calibration to calculate blood resistivity:
- Connect the Rho Cuvette to the Cuvette input on the front of the MPVS unit.The cuvette should have been prewarmed to the required temperature for at least 15mins.
- Select the Rho Cuvette tab in the MPVS software
- Select Create New Cuvette, and complete the details in the dialogue box (the details will be included with the cuvette). Your cuvette should then appear in the Millar Cuvette Selection table:
- Give the Cuvette a name and be sure to adjust the K factor which can be found on the cable of your Rho Cuvette
- Add a small amount of blood from the animal (approx 500uL) to the well of the Cuvette.Select Measure.
- The blood resistivity will be calculated, and the details will show at the bottom of the window
- Select Export, to export these details to the Catheter Configuration tab:
- The calculated resistivity will now be used in any volume calculations.
To use the Rho cuvette, the user must also have a method of calculating alpha. (Alpha is an electric field homogeneity factor). To calculate alpha it is necessary to know the cardiac output (CO) or stroke volume (SV). These can be measured using ultrasound for CO or thermodilution for SV. Compare the CO or SV from the thermo/ultrasound to the CO determined by the MPVS Ultra and calculate alpha (CO Ultra/COThermo/Ultrasound or SVUltra/SVThermo/Ultrasound). The resulting Value is entered into the box on the configuration tab.
Anytime a new alpha is entered or the number of segments changes, the user must recalibrate their volume in LabChart.