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Description
Measurements
Example:
f = 3/min = cycle time (1/f) = 20 seconds
T
Apnoea > = 15 seconds
This system is designed to prevent mandatory ventilation being
prematurely triggered in the event of irregular spontaneous
breathing, whilst at the same time giving an alarm for any long
period of low ventilation.
Measurements
Flow measurement
Regardless of whether ventilation is volume-controlled or
pressure-controlled, positive pressures are generated in both
the breathing system and patient lung during the inspiration
phase. Depending on the ratio of lung compliance to hose
system compliance, the volume delivered by the ventilator is
distributed to the patient's lung and to the hose system
installed between the ventilator and patient. Deviations in the
measured expiration flow and derived values, such as the
minute volume and breath volume, are low for adult patients,
due to their relatively high lung compliance in relation to the
much lower compliance of the ventilation hoses.
However, since only the volume attained and surrendered by
the lung is relevant to the efficiency of ventilation, and since
higher differences are possible during paediatric ventilation,
Evita 2 dura provides basic compensation for hose
compliance during ventilation.
Compensation of the effect of hose system compliance
During the device check before ventilation, Evita 2 dura
determines the compliance of the ventilation hoses, and then,
during ventilation, compensates for the effect of compliance
on volumetric flow measurement.
Depending on the airway pressure, Evita 2 dura increases the
tidal volume by the amount that remains in the ventilation
hoses.
In addition to hose system compliance, flow/volume
measurement is influenced by the environmental factors of
temperature and humidity and by leaks in the hose system.
Evita 2 dura takes these factors into account and corrects the
settings and measured values accordingly.
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