Acoustic Patient Sensor Coupler with Pressure Equalization
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Solution Overview
Problem
Piezoelectric membranes used in acoustic respiratory monitoring systems face variability in performance due to skin elasticity and attachment force, leading to inconsistent signal outputs, and existing systems struggle with noise compensation in noisy environments.
Innovation Solution
The implementation of an acoustic sensor system with pressure equalization pathways and multiple sensing elements, where the sensing elements are configured to provide both physiological and noise signals, allowing for adaptive filtering and noise attenuation to enhance signal-to-noise ratio and reduce variability in sensor performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If piezoelectric membranes are used for acoustic signal detection, then the sensor can detect a wide frequency range with low acoustical impedance, but the sensor performance varies due to skin elasticity and attachment force
Solution Approach 1:
An acoustic coupler is introduced as an intermediary component between the piezoelectric membrane and the patient's skin. The coupler includes a compressible member that adapts to skin elasticity variations, and an acoustic membrane that transmits body sounds to the piezoelectric sensor. This intermediary structure isolates the sensor from direct contact with varying skin surfaces, maintaining consistent acoustic coupling despite differences in skin elasticity and attachment force.
Solution Approach 2:
The acoustic coupler's compressible member changes its physical parameters (compression level, contact area) in response to skin elasticity variations. By allowing the coupler to adapt its compression state, the system maintains optimal acoustic coupling pressure regardless of whether the skin is elastic or firm, thereby preserving reliable and consistent signal output across different patients and attachment conditions.
2Reliability
If the sensor is tightly attached to the patient's skin, then acoustic coupling is improved, but skin elasticity and attachment force variability cause inconsistent cavity resonance
Solution Approach 1:
The acoustic coupler serves as a mediator that decouples the relationship between attachment force and cavity resonance. The compressible member absorbs variations in attachment pressure, while the acoustic membrane provides a consistent interface to the piezoelectric sensor. This allows the system to maintain stable cavity resonance characteristics even when attachment force varies, as the coupler isolates the resonant cavity from external pressure fluctuations.
3Measurement precision
If multiple sensing elements are used to capture physiological signals, then signal detection capability is enhanced, but noise interference from the environment and patient increases
Solution Approach 1:
A dedicated noise reference sensor is extracted and positioned to capture only environmental and patient-generated noise without physiological signals. This separate noise channel is then used in signal processing to identify and subtract noise components from the physiological signal channels, effectively removing harmful noise interference while preserving the desired physiological information.
Solution Approach 2:
Different sensing elements are assigned different functional qualities: some elements are optimized for physiological signal detection while others are designated as noise reference sensors. The noise reference sensors are strategically positioned to capture only noise, creating localized measurement zones with distinct quality characteristics. This functional differentiation allows the system to process and eliminate noise while preserving physiological signals.
4Reliability
If the acoustic coupler uses a compressible member to adapt to skin elasticity, then attachment variability is compensated, but the device complexity increases
Solution Approach 1:
The acoustic coupler employs a compressible member made from flexible, elastomeric material that naturally adapts to skin elasticity variations through passive mechanical deformation. This flexible structure eliminates the need for active control mechanisms, sensors, or complex adjustment systems, achieving reliable performance compensation across different skin types through simple material properties and geometric design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides accurate and robust measurement of bodily sounds, reducing noise interference and variability in sensor performance across different skin types and attachment forces, resulting in improved signal quality and reliability.
Implementation Method 1
The 'piezoelectric effect' is the appearance of an electric potential and current across certain faces of a crystal when it is subjected to mechanical stresses. Due to their capacity to convert mechanical deformation into an electric voltage, piezoelectric crystals have been broadly used in devices such as transducers, strain gauges and microphones.
Implementation Method 2
The sensing elements and frame define a cavity in which the sensing elements vibrate in response to acoustic signals received from a medical patient
Data Source
AI summary
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.