Fluke VT Plus HF, Operator'S Manual, Page: 128 / 134

VT Plus HF
Operators Manual
A-2
Low Flow
The VT PLUS HF has a low-flow (
±
25 LPM), bi-directional flow measurement. The
flow measurements can be either static (no breath variations) or ventilator waveforms
(i.e., both an expiratory and an inspiratory phase). Flow measurements are made using a
differential pressure drop across a resistive screen mesh. The low-flow signal can be used
for infant/neonatal ventilators or for determining the performance of many other types of
flowmeters. Valves are used to switch between the low-flow and the high-flow
measurements depending on the range selected in the display flow screens (see
Chapter
5, Display Screens ).
Airway Pressure
The airway pressure is measured from a tap off of the proximal (near the exhaust port) of
the flow sensor housings. This tap is connected to a
±
120 cmH
2
O pressure sensor that
generates the airway pressure signal. Valves are used to switch between the low-flow and
the high-flow measurements. When the low-flow port is selected, the airway pressure is
measured off the low-flow port. Likewise, when the high-flow port is selected the airway
pressure is measured off the high-flow port. Use the soft key below
RANGE
from any of
the flow screens to select which flow port (high or low) airway pressure is measured
from.
Low Pressure
This is a dual-port connection consisting of a "+" positive and a "-" negative pressure
port. The differential pressure range is ± 500 mmHg. This pressure measurement can be
used for any pressure differential or gauge pressure in the given range. The transducer is
capable of measuring fluid pressure on the “+” positive port as indicated on the label.
Barometric Pressure
A barometric pressure measurement is provided by the VT PLUS HF . The barometer can
read absolute pressures from 8 to 18 PSIA. The barometer is also used in the automatic
ATP, BTPS, and STPD conversions for flow and volume measurements. The barometric
pressure signal can be fine tuned using the setup described in
Chapter 3, System Setup .
High-Pressure Measurement
The high-pressure measurement is made from a dual-port connection consisting of a "+"
positive and a "-" negative pressure port. The differential pressure range is ± 100 psi. This
pressure measurement can be used for any pressure differential or gauge pressure in the
given range. The transducer is capable of measuring fluid pressure on the “+” positive
port as indicated on the label.
Oxygen Concentration
Oxygen is measured through the high-flow port of the system on the rear panel bulkhead
fitting. The range for this sensor is 0% to 100%. The oxygen cell is mounted inside the
enclosure on the rear bulkhead for the high-flow circuit. The fuel cell will need to be
replaced approximately once a year. Oxygen readings are compensated for airway
pressure.