A SILICON BIDIRECTIONAL FLOW SENSOR FOR MEASURING RESPIRATORY FLOW

We describe a solid-state, silicon integrated, bidirectional flow sens or for respiratory applications. The sensor is a thermal vector sensor . The electronic circuitry for obtaining bidirectional sensitivity is presented together with actual application to a healthy volunteer put on mechanical ventilation. The sensor's input how range is from -60 to +60 L/min, and its rise-time is less than or equal to 40 ms and fall- time is less than or equal to 60 ms. The effect of changes in gas comp osition as used in mechanically ventilated patients on the sensor outp ut signal are estimated to be less than 2%. The temperature sensitivit y is about -1.5% per degree Celsius.