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Figure 1-5. Flow sensor
The area of the orifice changes depending on the flow rate.
It opens progressively as the flow increases, creating a pressure
drop across the orifice. The pressure difference is measured by
a high-precision differential pressure sensor inside the ventila-
tor. The pressure difference varies with flow (relationship deter-
mined during flow sensor calibration), so the patient’s flow is
determined from the pressure drop. The device calculates
volume from the flow measurements.
The flow sensor is highly accurate even in the presence of
secretions, moisture, and nebulized medications. The device
continuously flushes the sensing tubes with mixed gases (rinse
flow) to prevent blockage.
1.3 Physical description
1.3.1 Breathing circuits and accessories
NOTE:
To ensure proper ventilation operation, use parts and
accessories specified in Table 1-1 only.
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