What are the steps to calibrate the MPVS-400 Pressure-Volume System in LabChart?

The MPVS-400 Pressure-Volume System, a Millar Instruments discontinued product, can be calibrated in LabChart by following the steps listed below:

  • Connect the MPVS-400 to the computer using the USB cable provided, ensure that the appropriate version of the LabChart software for the computer's operating system is installed. 
  • Turn on the MPVS-400 using the power switch located on the back panel. Ensure that the Power Indicator and Status Indicator located on the front panel are both illuminated. 
  • Launch LabChart, and ensure that the MPVS-400 has been identified correctly in the software.  Configure LabChart to show the desired number of channels for the experiment in the Chart View.
  • Connect the catheter adapter cables to the appropriate input connectors on the back of the MPVS-400. Connect the second pressure catheter adapter cable and the auxiliary analog input BNC cable if desired. 

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  • Connect the pressure transducer and volume transducer connectors on the P-V catheter to the catheter adapter cable. 
  • Using a shallow dish, beaker, or syringe, soak the catheter tip in body temperature sterile water or saline for at least 30 minutes before proceeding.
  • Verify that the appropriate segment length has been selected using the Segment Select switch on the front panel of the MPVS-400. For standard four-electrode P-V catheters, select the “Short” position. For six-electrode P-V catheters, select either the “Short” or the “Long” position depending on the desired electrode spacing (segment length).

 Pressure Calibration

  • Left mouse click the Start/Stop button in LabChart to begin recording from the MPVS unit.

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  • Set the Pressure Transducer/Calibration switch on the front panel of the MPVS-400 to Transducer. Unlock and adjust the Balance control knob for the pressure channel connected to the catheter. Use the Balance control knob to adjust the pressure transducer output while dipping the transducer just below the surface of sterile water or saline (essentially a zero pressure environment). Adjust the Balance control knob until the output signal reads approximately 0 Volts (as displayed by LabChart in the Pressure channel) then lock the knob into position.  For best stability and zero adjustment, shield the sensor from bright ambient light during the balancing procedure. Zero balancing of the pressure transducer should be done prior to each catheterization procedure.
  • While still recording in LabChart, set the Pressure Transducer/Calibration switch on the front panel of the MPVS-400 to 0 mmHg.  Leave the switch in this position for 5-10 seconds.  Move the Pressure Transducer/Calibration switch to the 100 mmHg position, and leave it in this position for 5-10 seconds.  Return the switch to the Transducer position, and left mouse click the Start/Stop button in in LabChart to stop recording
  • Repeat the previous 3 steps if an additional pressure transducer is connected to the MPVS-400.
  • There will now be a recording of known voltages for specific catheter pressure values.  With these values, LabChart can apply a Units Conversion to the pressure channel with either the Units Conversion Channel Calculation or the PV-Loop module (Windows only) workflow feature. The pressure calibration may be verified using an external manometer (digital or mercury).

Volume Calibration

To calibrate the volume electrodes, left mouse click the Start/Stop button in LabChart to begin recording from the MPVS unit.

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  • Set the Volume Control switch on the front panel of the MPVS-400 to 5 RVU. Leave the switch in this position for 5-10 seconds. Move the Volume Control switch to the 50 RVU position, and leave it in this position for 5-10 seconds. Return the switch to the Transducer position, and left mouse click the Start/Stop button in in LabChart to stop recording
  • There will now be a recording of known voltages for specific RVU values. With these values, LabChart can apply a Units Conversion to the volume channel with either the Units Conversion channel calculation or the PV-Loop module (Windows only) workflow feature. Validation of the volume estimates provided by the Millar hardware can be performed by other means, e.g. by thermodilution, flow probes, hypertonic saline dilution, echo, etc.