Acoustic respiratory monitoring sensor having multiple sensing elements
According to certain described aspects, multiple acoustic sensing elements are employed in a variety of beneficial ways to provide improved physiological monitoring, among other advantages. In various embodiments, sensing elements can be advantageously employed in a single sensor package, in multiple sensor packages, and at a variety of other strategic locations in the monitoring environment. According to other aspects, to compensate for skin elasticity and attachment variability, an acoustic sensor support is provided that includes one or more pressure equalization pathways. The pathways can provide an air-flow channel from the cavity defined by the sensing elements and frame to the ambient air pressure.
1. An acoustic sensor comprising:
first and second piezoelectric elements each including respective first and second electrodes; and
a noise attenuator coupled to the first electrode of the first piezoelectric element and the first electrode of the second piezoelectric element, the noise attenuator configured to:
at least partially constructively combine a physiological signal component of a first signal output by the first piezoelectric element and a physiological signal component of a second signal output by the second piezoelectric element; and
at least partially destructively combine a noise component of the first signal output by the first piezoelectric element and a noise component of the second signal output by the second piezoelectric element.
2. The acoustic sensor of claim 1 , wherein the first piezoelectric element and the second piezoelectric element are arranged in a stack, and wherein the second electrode of the first piezoelectric element and the second electrode of the second piezoelectric element are coupled to a common potential.
3. The acoustic sensor of claim 2 , wherein the first and second piezoelectric elements each comprise:
first electrode coatings disposed on surfaces of the respective piezoelectric elements corresponding to an outer portion of the stack; and
second electrode coatings disposed on surfaces of the respective piezoelectric elements corresponding to an inner portion of the stack,
wherein the first electrode coatings are configured to shield the second electrode coatings from electromagnetic noise.
4. The acoustic sensor of claim 1 , wherein the noise attenuator comprises at least one of: circuitry including an amplifier, a signal processor, or a general-purpose processor.
5. The acoustic sensor of claim 1 , wherein the noise attenuator is further configured to generate a reduced noise signal based on constructively combining the physiological signal components and destructively combining the noise components.
6. The acoustic sensor of claim 5 , wherein the reduced noise signal has a lower noise component than one or more of the first and second signals.
7. The acoustic sensor of claim 5 , wherein the noise attenuator generates the reduced noise signal using common-mode rejection.
8. The acoustic sensor of claim 1 further comprising:
a coupling bump configured to apply pressure to at least one of the first and second piezoelectric elements to push at least a portion of the one of the first and second piezoelectric elements into a cavity of the acoustic sensor.
9. The acoustic sensor of claim 8 , wherein the coupling bump is configured to transmit acoustic vibrations to the one of the first and second piezoelectric elements through the acoustic coupling bump when the acoustic sensor is attached to the medical patient.
10. A method comprising:
receiving signals from an acoustic sensor that is attachable to a medical patient and configured to provide the signals responsive to acoustic vibrations indicative of one or more physiological parameters of the medical patient, the acoustic sensor including first and second piezoelectric elements each including respective first and second electrodes; and
by a noise attenuator:
at least partially constructively combine a physiological signal component of a first signal output by the first piezoelectric element and a physiological signal component of a second signal output by the second piezoelectric element; and
at least partially destructively combine a noise component of the first signal output by the first piezoelectric element and a noise component of the second signal output by the second piezoelectric element,
wherein the noise attenuator is coupled to the first electrode of the first piezoelectric element and the first electrode of the second piezoelectric element.
11. The method of claim 10 , wherein the first piezoelectric element and the second piezoelectric element are arranged in a stack, and wherein the second electrode of the first piezoelectric element and the second electrode of the second piezoelectric element are coupled to a common potential.
12. The method of claim 11 , wherein the first and second piezoelectric elements each comprise:
first electrode coatings disposed on surfaces of the respective piezoelectric elements corresponding to an outer portion of the stack; and
second electrode coatings disposed on surfaces of the respective piezoelectric elements corresponding to an inner portion of the stack,
wherein the first electrode coatings are configured to shield the second electrode coatings from electromagnetic noise.
13. The method of claim 10 , wherein the noise attenuator comprises at least one of: circuitry including an amplifier, a signal processor, or a general-purpose processor.
14. The method of claim 10 further comprising:
by the noise attenuator, generating a reduced noise signal based on constructively combining the physiological signal components and destructively combining the noise components.
15. The method of claim 14 , wherein the reduced noise signal has a lower noise component than one or more of the first and second signals.
16. The method of claim 14 , wherein the noise attenuator generates the reduced noise signal using common-mode rejection.
17. The method of claim 10 , wherein the acoustic sensor further includes a coupling bump configured to apply pressure to at least one of the first and second piezoelectric elements to push at least a portion of the one of the first and second piezoelectric elements into a cavity of the acoustic sensor.
18. The method of claim 17 , wherein the coupling bump is configured to transmit acoustic vibrations to the one of the first and second piezoelectric elements through the acoustic coupling bump when the acoustic sensor is attached to the medical patient.
19. A method comprising:
at least partially constructively combining, by a noise attenuator, a physiological signal component of a first signal received from a first piezoelectric element of an acoustic sensor and a physiological signal component of a second signal received from a second piezoelectric element of the acoustic sensor; and
at least partially destructively combining, by the noise attenuator, a noise component of the first signal received from the first piezoelectric element and a noise component of the second signal received from the second piezoelectric element,
wherein the noise attenuator is coupled to a first electrode of the first piezoelectric element and a first electrode of the second piezoelectric element.
20. The method of claim 19 , wherein a second electrode of the first piezoelectric element and a second electrode of the second piezoelectric element are coupled to a common potential.
21. The method of claim 20 , wherein the first and second piezoelectric elements are each stretched from a first side of a cavity of the acoustic sensor to a second side of the cavity of the acoustic sensor.