Hoffrichter TRENDvent, Руководство пользователя

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How the device works 25
HOW THE DEVICE WORKS
The function of the TRENDvent ventilator is based on a control mecha-
nism, which adjusts the power of the blower to the air output required for
therapy in a closed loop. The blower power is controlled by the signal of
the respiratory pressure and the signal of the inspiration
fl ow.
Starting the device (initialization)
When the device is started, the parameters are read from the memory
(EEPROM) and checked for validity. The pressure, the
fl ow sensor and the
acoustic alarm are also tested. In the event of an error, the error detection
is saved and shown on the screen.
The calibration data is loaded from the EEPROM and tested for validity.
If an oxygen sensor is connected, it is calibrated against the ambient air.
Parameter measurement
The device’s analog measurements are read in and analyzed. Target val-
ues are calculated on the basis of the set parameters and/or ventilation
modes. Then the target values are transferred to the motor control via a
digital-to-analog converter (DAC).
The proximal pressure, the valve-control pressure and inspiration fl ow
are measured. This data is used to calculate the inspiration volume and
respiratory frequency. In addition, the actual patient
fl ow is calculated by
subtracting the leakage fl ow. If an oxygen sensor is present, the oxygen
content of the inspiration air FiO
2
is measured.
The pressure or fl ow sensor detects the patient’s spontaneous respiration
and sets off the triggers, which compensate mask leaks. The sensitivity
of the trigger is adjustable. The inspiration trigger is a pressure or volume
trigger. The expiration trigger is a fl ow trigger, which is set as a percent-
age of the maximum inspiration fl ow.