EvitaXL

Measurements
Automatic leakage compensation
Automatic leakage compensation
EvitaXL 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 EvitaXL as the leakage minute
volume MVleak.
EvitaXL can compensate for this leakage in volume-controlled
ventilation.
Example:
Tidal volume setting VT = 500 mL, 10 % leakage in tube.
Leakage compensation Off
EvitaXL delivers 500 mL. This value is indicated as VTi. 50 mL
escape as leakage during inspiration, and 450 mL reach the
lung. 450 mL are expired, and 45 mL again escape as leakage.
A tidal volume of 405 mL is measured on the expiration side
and indicated as VTe.
With a ventilation rate of 10 strokes per minute, a minute volume
of 5.0 L/min is delivered on the inspiration side and a
minute volume of 4.05 L/min is measured on the expiration
side. The lung is ventilated with an MV of 4.5 L/min.
Without leakage compensation, the set VT determines the
volume delivered by EvitaXL.
Leakage compensation On
With automatic leakage compensation, EvitaXL delivers
550mL tidal volume on the basis of the measured leakage
minute volume, instead of the 500mL set. 500 mL reach the
lung and the inspiratory tidal volume is 500 mL. This value is
indicated as VT.
The volume of 450 mL measured on the expiration side is displayed
without compensation, even when leakage compensation
is activated. The minute volume measured on the
expiration side is 4.5 L/min and is also uncompensated.
If this were not so, the alarm for a low minute volume could be
inhibited by the expiratory leakage compensation. EvitaXL must
always emit an alarm if the minute volume is too low.
With leakage compensation, the set VT determines the
volume to be delivered to the patient.
This example has been simplified:
In fact, the calculated leakage correction takes into account
the pressures in the hose system. A higher percentage volume
is lost on the inspiration side than on the expiration side
because the pressure during inspiration is higher.
The displayed leakage minute volume MVleak is based on the
mean pressure Pmean.
The leakage minute volume MVleak also takes the inspiratory
leaks into account. The sum of the minute volume MV + the
leakage minute volume MVleak is consequently greater than
the inspiratory minute volume delivered to the patient.
220 Instructions for Use EvitaXL