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6.6.2 Leakage compensation
The leakage from the breathing circuit and mask may cause that the gas volume delivered to
the patient’s lung is lower than the setting value. The leakage also may cause the false
inspiratory trigger or difficult switching between inspiratory and expiratory.
The ventilator provides automatic leakage compensation function. The ventilator updates the
amount of leakage at the end of each breathing cycle according to the difference between the
inspired tidal volume and expired tidal volume, and the amount of leakage can be used for the
calculation of real-time leakage flow in next breathing cycle.
During the expiration stage, the base flow will be regulated automatically to compensate the
leakage and maintain the PEEP valve. In order to prevent the false inspiratory trigger, flow
trigger working mechanism is based on the compensated flow. Maximum leakage
compensation flow is 65 L/min for adults and 45 L/min for pediatrics.
In volume control ventilation mode, the delivered gas volume is the sum of the setting TV
and the amount of leakage. The leakage compensation in invasive ventilation: the upper limit
of the leakage compensation is 80% of the setting TV.
In pressure control ventilation mode, the ventilator regulates the flow automatically to
compensate the leakage in order to maintain the inspiratory pressure. But the upper limit of
the compensation is restricted by the TV high limit. The ventilator will not increase the flow
and display the [Volume Limited] alarm message when the flow exceeds the TV high limit
(If you want to reach the maximum leakage compensation, you can set the TV high limit to
off).
Automatic leakage compensation
The ventilator determines the difference between the delivered flow on the inspiration side
and the measured flow on the expiration side.
This difference provides a measure of the amount of leakage and is displayed by the
ventilator as the leakage minute volume MVleak.
The ventilator can compensate for this leakage in volume controlled ventilation.
Example: Tidal volume setting TV = 600 mL, 10 % leakage in tube.
Without Leakage compensation
The ventilator delivers 600 mL. This is indicated as the inspiratory tidal volume TVi. 60 mL
escape as leakage during inspiration, and 540 mL reach the lung.
540 mL are expired, and 40 mL again escape as leakage. A tidal volume of 500 mL is
measured on the expiration side and indicated as TVe.
With a ventilation rate of 10 strokes per minute, a minute volume of 6.0 L/min is delivered on
the inspiration side and a minute volume of 5.0 L/min is measured on the expiration side. The
lung is ventilated with an MV of 5.4 L/min.
Without leakage compensation, the set TV determines the volume delivered by the ventilator.
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