Fluke Biomedical VT Plus HF - Manual (Page 81)

Operation
Special Functions
3
3-31
Assist Test
The Assist test determines the sensitivity of the ventilator in patient assist mode and helps
to calibrate the full range of assist pressures under which the ventilator can operate.
During an assisted breath, the airway pressure drops during the inspiration due to the
spontaneous breath. The assist is triggered by a negative pressure (relative to the end-
expiratory pressure) during the expiratory hold period. See Figure 3-2.
AIR W AY
PRESSURE
ASSISTED
BREATH
TIME
N ORMAL
BREATH
O
MI N IMUM AIR W AY
PRESSURE
EEP
fec072.eps
Figure 3-2. The Assist Test
To perform an Assist test:
1. Press the
FULL/5 key. The Full Test screen displays.
2. Connect the ventilator breathing circuit to the Analyzer in the bidirectional
measurement configuration as shown in Figure 3-3.
O u tlet Inlet
V entilator
Inspiratory Hose
Expiratory Hose
Analyzer
TEST
LU
N G
fec002.eps
Figure 3-3. Ventilator Breathing Circuit Setup for Bi-Directional Measurements
3. Adjust the ventilator controls so that the ventilator is triggered by an effort (negative
pressure) at the lung during the expiration hold period of the ventilator's breath cycle.
Note
Use the Synchronized Intermittent Mandatory Ventilation (SIMV) mode or
Intermittent Demand Ventilation (IDV) mode if the ventilator provides it.
4. Check the control setting by applying upward force at the back of the test lung and
observing if the ventilator triggers as desired.
5. Set a low breath rate to allow the distinction to be made between a triggered assist
breath and a mandatory breath.