D-8 624074/07
D NIV (Noninvasive ventilation)
D.8 Alarms
Volume alarms are less meaningful in noninvasive than in other
modes, because of the unpredictable gas leakage in these
modes. Alarms are based on the returned expiratory gas vol-
ume measured at the flow sensor; this value can be signifi-
cantly lower than the delivered tidal volume, because the
delivered tidal volume is the sum of the displayed VTE and the
leakage volume. To avoid nuisance volume alarms, set the low
Vt and ExpMinVol alarms to a low level.
Because the noninvasive modes are pressure modes, however,
do pay attention to the pressure-related alarms. If the defined
PEEP and inspiratory pressure can be maintained, the ventilator
is compensating the gas leak sufficiently.
D.9 Monitored parameters
NOTE:
• Due to the changing and unpredictable amount of
leakage, the following numeric monitoring parame-
ters cannot be used for reliable analysis of patient
conditions: RCexp, Rinsp, Insp Flow, AutoPEEP, and
Cstat. Continuous monitoring of the clinical parame-
ters and patient comfort is of critical importance.
• The parameters VTE NIV, ExpMinNIV, MVSpoNIV and
MVLeak are leak compensated, and are used in non-
invasive modes. These parameters are estimations
and may not reflect exact values.
Due to the leakage at the patient interface, displayed exhaled
volumes in the noninvasive modes can be substantially smaller
than the delivered volumes. The flow sensor (a bidirectional
device proximal to the patient) measures the delivered volume
and the exhaled tidal volume.
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