Flow estimation and compensation of flow-induced pressure swings in CPAP treatment and assisted respiration
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United States of America Patent
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Dec 25, 2001
Grant Date -
N/A
app pub date -
Nov 17, 1997
filing date -
Sep 15, 1995
priority date (Note) -
In Force
status (Latency Note)
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Abstract
A method of flow estimation during CPAP treatment is disclosed and involves measuring turbine (32) speed by means of the motor's Hall-effect sensors (80). The equivalent pressure, p.sub.est, that would be developed by the turbine (32) for the measured speed if the flow were zero is estimated using a predetermined mathematical function. Coincidentally with the speed measurement and pressure estimation, the delivery tube pressure, p.sub.act, is measured by the pressure transducer (42), and from p.sub.act together with p.sub.est, the difference between the two pressures is calculated, representing an estimation of flow, f.sub.est. The flow estimation value can be linearised by the square root device (86), and then filtered by the combination of low pass and high pass filters (90, 92) to derive a filtered flow estimate value, that has the non-respiratory components removed. A method of flow compensation of flow-induced pressure swings also is disclosed.
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