Millar MPVS Duo: Admittance Set Up

In this demonstration video Mark de Reus, Head of Training and Support at ADInstruments, shows you how to set up the MPVS Duo for Admittance PV recordings.

Step 1: Connect the hardware

Step 2: LabChart Preparation

Step 3: Turning it on

  • Switch on the MPVS Duo by pressing the power button on the MPVS Duo keypad.

Step 4: LabChart Set Up

  • Open LabChart on your computer.
  • Close the ‘Welcome Centre’ pop-up.
  • Click ‘Setup’ from the menu bar at the top of the page.
  • Select ‘Channel Settings’ from the ‘Setup’ dropdown menu, this will trigger a pop-up box to appear with your channels and their settings.
  • Reduce the number of channels to 4.
  • Give the channels the following names:
    • Channel 1 = Pressure
    • Channel 2 = Volume
    • Channel 3 = Phase
    • Channel 4 = Magnitude
  • Click ‘Ok’

Step 5: MPVS Duo Start Up

  • After LabChart set up the MPVS Duo will initialize
  • Connect a catheter
  • Press 1 on the keypad to start a new PV Loop protocol
  • Press 1 to select Admittance
  • You will be prompted to soak the catheter for 30 minutes, if you have already soaked the catheter for 30 minutes simply press the ‘>’ button on the keypad to move forward with calibration.
  • In LabChart select ‘PV Loop’ from the menu bar, and then select ‘Workflow’ from the dropdown menu, this will open the workflow menu on the left of your screen.
    • If this option is greyed out select ‘Workflow mode…’ instead. This will bring up a PV Loop Workflow Mode pop-up. Check that the ‘Enable PV Loop Workflow’ box at the bottom of the pop-up is ticked.

Step 6: Setup PV Loop Channels

  • The PV Loop Workflow menu will open on the left side of your LabChart screen. Within the ‘Setup PV Loop’ section there are five dropdowns, set them to the following options:
    • Select Workflow = MPVS Duo - Admittance
    • Pressure Channel = Ch1: Pressure
    • Volume Channel = Ch2: Volume
    • Phase Channel = Ch3: Phase
    • Magnitude Channel = Ch4: Magnitude
  • Once all five are filled out a green checkmark will appear next to the ‘Setup PV Loop’ heading.

Step 7: Duo Channel Calibration

  • Select the next heading in the setup list; ‘Duo Channel Calibration’
  • To begin, you will need to select the type of catheter you are using from the ‘Duo Catheter’ dropdown menu. These are limited to: mouse, rat, five sizes of ventri-cath, or a manual option if you would like to enter all of the values from scratch.
  • We recommend using actual voltage values from the MPVS Duo, as there could be variation between systems.
  • To produce actual voltage values:
    • start LabChart by pressing the ‘Start’ button at the bottom right of the screen.
    • On the MPVS Duo, press 1 on the keypad to go the low voltages screen.
    • Press 0 to output this to LabChart.
    • Record for a couple of seconds.
    • Press the ‘<’ arrow on the MPVS Duo to go back to the calibration screen.
    • Press 2 on the keypad to go to the high voltages screen.
    • Press 0 to output this to LabChart.
    • Record for a couple of seconds.
    • Press the ‘<’ arrow again to go back to the calibration screen.
    • Stop the recording in LabChart by pressing the ‘Stop’ button at the bottom right of the screen.
    • To enter the values for the pressure channel:
      • Select the area of the graph before the bump in voltage, and add that to the calibration box next to 0mmHg.
      • Select the area of the graph after the bump in voltage, and add that to the calibration box next to 100mmHg.
      • Tick the ‘Apply pressure calibration’ box below the calibration values.
    • Repeat the above process for the volume, phase, and magnitude channels.

Step 8: Balancing The Pressure Sensor

  • Start LabChart by pressing the ‘start’ button in the bottom right corner.
  • On the MPVS Duo, press the ‘>’ arrow to move on to the ‘Balance Pressure’ screen.
  • Press 1 on the keypad to balance the pressure sensor in the PV catheter.
  • Press 1 again to zero the pressure.
  • The current reading on the MPVS Duo, and in LabChart, should drop to zero.
  • Stop LabChart by pressing the ‘stop’ button in the bottom right corner.
  • Press the ‘<’ arrow on the MPVS Duo to go back to the Balance Pressure Sensor screen.
  • Press the ‘>’ arrow to move on to the Calibration Parameters screen.

Step 9: Determining Calibration Parameters

Step 10: Optimizing Catheter Position

  • In LabChart, move to the Sampling section of the PV Loop Workflow.
  • Click the ‘Start’ button beside ‘Start Sampling’.
  • On the MPVS Duo, press the ‘>’ arrow to open the Optimize Catheter Position screen.
  • Insert the catheter into the ventricle.
    • For small animal catheters, only one segment selection is available, so you can press the ‘>’ arrow on the MPVS Duo when ready.
    • For larger animal catheters, select the segment with a size suitable for the animal’s ventricle. Press 1 on the MPVS Duo, enter the segment number, and then press ‘OK’.
  • Press 5 to turn on a low pass filter (non-compulsory).
  • Check the manual to determine the specified ranges for ‘phase’ and ‘magnitude’. Use these ranges to guide your placement of the catheter within the ventricle.
  • Once your catheter positioning is optimal, press the ‘>’ arrow on the MPVS Duo to move into experimental mode.

Step 11: Experimental Mode

  • Now it is time to follow your experimental protocol; recording baseline and occlusion data.

Step 12: After the Experiment

  • In LabChart, once the experiment is complete, stop recording and tick the ‘Sampling Complete’ box in the PV Loop Workflow.
  • The data is now ready to be analyzed using the ‘Analysis’ section of the PV Loop Workflow.