DATREND Systems vPad-IV, Operating Manual

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vPad-IV OPERATORS MANUAL
4.3.3.6 Pressure zero
Referring to
Figure 23 , the Zero button on the test configuration menu enables the pressure measurement
to be zeroed. This should be done only when pressures at the input and output of the Module are known to
be zero. When a Module is in the primed state, it is best to set the zero when there is no infusion device
connected to the input port and when input and output tubing sets are lying flat along the test bench so that
hydrostatic pressure or vacuum applied to the Module is reduced as much as practical. This approach will
improve accuracy of the zero calibration and thus accuracy of pressure measurements overall. Under no
circumstances should the pressure be zeroed while an infusion device is actively pumping into the Module's
input as such pumping is likely to cause the pressure at the Module input to be increased above zero.
The pressure zero offset of a Module is affected by altitude above sea level and to a lesser extent by the local
weather. To accommodate use of vPad-IV over a wide range of geographic locations and environmental
conditions, the app allows the zero to be adjusted over a range of -225 to +60 mmHg from the default sea-
level reference. The app will display an error message if the user attempts to set the zero outside the
permitted range of adjustment, in which case the user should carefully inspect the test setup to confirm no
significant pressure or vacuum is being applied to the Module when the
Zero button is pressed.
To assist the user in zeroing the Module appropriately, the app displays a confirmation dialog if the change
in the zero offset will exceed ±25 mmHg from its current setting. As previously stated, zeroing of the
pressure measurement should be done only when pressures at the input and output of the Module are
known to be zero, which is most accurately achieved with no infusion device connected to the input port
and with input and output tubing sets lying flat along the test bench. If this is the case, press "OK" on the
confirmation dialog to set the zero, or otherwise make adjustments to the test setup to reduce the pressure
applied to the Module and repeat.
The most accurate zero calibration is obtained when the Module is completely empty of water and its input
port is open to the atmosphere when the zero is taken. vPad-IV provides two different methods of
obtaining such a zero reference: the channel's zero offset will be updated automatically if the Module is
found to be completely empty at app startup, or alternatively, the Module may be drained during setup of an
Occlusion Pressure Test and the
Zero button pressed with the Module in this state. Respectively refer to
Section 4.2 on page 27 and Section 4.3.7 on page 39 for further details.
Zero pressure offsets are stored for each channel individually. Previously-stored offsets can be individually
or collectively reset via the app's
Setup menu (see Section 4.8.7.2 on page 71).
Operation/Chapter 4
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