624074/07 B-25
B.6 Leak compensation
For an invasive ventilator to function properly, no significant
leaks can be present anywhere in the entire system, including
ventilator, breathing circuit, and patient respiratory system. For
optimal ventilator performance, leakage must be stopped or
minimized rather than compensated.
The difference between the inspiratory flow delivered to the
patient, and the patient’s expiratory flow, as measured by the
proximal flow sensor, is a way of measuring the amount of
leakage in the circuit.
Early recognition is the key to stopping leakage. Using the
proximal flow sensor, this device can distinguish between
leakage at the breathing circuit from leaks on the patient side.
The benefits are:
• Detection and notification of the presence of leakage plus
its location (that is, tubing or patient side).
• Display of the actual exhaled tidal volume (VTE) so the
clinician can easily note any discrepancy between set and
exhaled tidal volumes.
• Display of the leak volume (VLeak) breath by breath. VLeak
is determined as the difference between delivered (inspira-
tory) tidal volume and exhaled tidal volume. It is displayed
in mL and also as a percentage of total tidal volume. Note
that VLeak indicates the leak at the patient side only.
In all pressure modes, the device automatically compensates
for leakage by adjusting gas delivery to achieve and maintain
the set pressure profile.
With its IntelliTrig function, the ventilator can automatically
adapt to changing breath patterns and system leaks to achieve
optimum synchronization between patient and device.
To synchronize, IntelliTrig compensates any leaks and resis-
tances between the ventilator and the patient, and with each
breath it measures the leakage at the patient interface (mask).
With this information IntelliTrig adapts the trigger mechanism
so leakage and the changing breath pattern do not influence
the operator-set trigger sensitivity (flow trigger).
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