Infrasonic stethoscope for monitoring physiological processes
Inventors
Shams, Qamar A. • Zuckerwar, Allan J. • Dimarcantonio, Albert L.
Assignees
Analytical Services and Materials Inc • National Aeronautics and Space Administration NASA
Publication Number
US-9867591-B2
Publication Date
2018-01-16
Expiration Date
2035-03-16
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Abstract
An infrasonic stethoscope for monitoring physiological processes of a patient includes a microphone capable of detecting acoustic signals in the audible frequency bandwidth and in the infrasonic bandwidth (0.03 to 1000 Hertz), a body coupler attached to the body at a first opening in the microphone, a flexible tube attached to the body at a second opening in the microphone, and an earpiece attached to the flexible tube. The body coupler is capable of engagement with a patient to transmit sounds from the person, to the microphone and then to the earpiece.
Core Innovation
The invention is an infrasonic stethoscope (or infrascope) for monitoring physiological processes of a patient, which includes a microphone capable of detecting acoustic signals in both the audible frequency bandwidth and the infrasonic bandwidth (0.03 to 1000 Hertz). The device comprises a microphone body with first and second spaced-apart openings, a body coupler attached to the first opening forming a substantially air-tight seal and capable of engagement with the patient, a flexible tube attached to the second opening, and an earpiece attached to the flexible tube. The body coupler transmits sounds from the patient to the microphone and then to the earpiece for monitoring physiological processes.
The problem being solved addresses limitations in conventional stethoscopes and physiological monitors that detect only audible frequencies, lacking the capability to monitor infrasonic acoustic signals below 20 Hertz, which are inaudible but provide valuable information, especially as over 60% of the power spectral density of heart signals falls within the infrasonic bandwidth. High frequency acoustic signals experience high attenuation limiting tissue penetration, whereas lower frequencies, including infrasonic signals, have low attenuation and can offer better monitoring of heart performance and other physiological processes. The invention aims to provide a device capable of detecting both audible and infrasonic signals to enhance physiological monitoring, including cardiac, respiratory, and fetal heart monitoring.
The infrasonic stethoscope includes a sophisticated microphone design featuring a conductive backplate and conductive membrane forming a capacitor, and a preamplifier board configured to measure capacitance changes and convert them into voltage signals. The structure includes chambers within the microphone body to provide damping and flat frequency response across the desired range. The microphone and body coupler are designed to form a sealed acoustic system that can detect very low frequency signals down to 0.03 Hertz, allowing detection of infrasonic signals along with audible signals. The device supports wired or wireless transmission of digitized signals for real-time remote monitoring.
Claims Coverage
The patent presents multiple inventive features across two independent claims, focusing on the structural and functional aspects of the infrasonic stethoscope device.
Infrasonic stethoscope structure with low-frequency detection capability
The device has a body with an opening at a first end and an end wall at the opposite second end, with a side wall extending between. A body coupler is attached to the first end forming a substantially air-tight seal and engaging the patient. Inside the cavity formed by these components, a conductive backplate defines a backchamber, and a conductive membrane spaced apart from the backplate forms a capacitor. A preamplifier board electrically connects to the backplate, measures capacitance changes between membrane and backplate, converts these to voltage signals, is positioned parallel to both, and defines two chambers within the body. The device detects acoustic signals from 0.03 Hertz up to about 1000 Hertz, including infrasonic signals below 20 Hertz.
Damping and airflow features for membrane motion control
The conductive backplate defines multiple holes, and a slot exists between the outer diameter of the backplate and the inner surface of the body side wall. The size and position of these holes and slot are selected to produce substantially critically damped membrane motion to ensure a flat frequency response.
Supporting and insulating structure for electrical isolation and connectivity
A conductive support plate mounted inside the body includes a passageway and apertures. An insulating member extends through this support plate passageway, and a conductive member extends through the insulating member to electrically connect the conductive backplate on one side and the preamplifier board on the other side of the support plate, maintaining electrical isolation and connection integrity.
Acoustic impedance tuning via chamber volumes and slots
The preamplifier board defines first and second chambers with volumes approximately 0.1287 cubic inch and 0.6 cubic inch, respectively. A slot about 0.025 inches wide is formed between the preamplifier board outer diameter and the body side wall. This arrangement provides acoustic resistance and lowers the low-frequency limit for signal detection.
Body coupler design with flexible diaphragm and threaded connection
The body coupler includes an outer ring with a flexible, non-conductive diaphragm spanning its diameter and attaches to the body by threaded connection ensuring a sealed interface, enabling efficient sound transmission from the patient to the microphone.
Signal digitization and transmission capabilities
The device includes a sealed electrical connection through the body side wall for connecting to remote devices. Voltage signals from the preamplifier are digitized on a remote board and can be transmitted via wired or wireless modes, including real-time electronic transmission to remote locations.
Alternative embodiment with flexible diaphragm over body opening
An alternative construct comprises a flexible, non-conductive diaphragm extending over the body opening to engage the patient, with a preamplifier board inside the cavity parallel to the diaphragm, capable of detecting acoustic signals below about 20 Hertz, with conductive membrane and backplate forming a capacitor in between.
The claims cover an infrasonic stethoscope device with a specialized microphone and body coupler structure enabling detection of both audible and infrasonic acoustic signals, employing detailed acoustic damping and electrical configuration for sensitive capacitance measurement, along with sealed connection and signal transmission features for remote monitoring.
Stated Advantages
Enables monitoring of both audible and infrasonic frequencies, providing access to physiological information not available via conventional stethoscopes.
Allows detection of low-frequency heart and respiratory sounds with minimal attenuation, improving diagnostic capabilities.
Facilitates real-time transmission of physiological data to remote locations for immediate analysis and diagnosis.
Is relatively inexpensive and portable, suitable for early-stage abnormality diagnosis, including use in ambulances and remote healthcare settings.
Improves signal quality with high signal-to-noise ratio due to specialized microphone design and passive filtering in the body coupler.
Documented Applications
Cardiac monitoring, including detection of heart sounds S1, S2, S3, and S4 and murmurs.
External fetal monitoring to track fetal heart rate and uterine contractions during pregnancy and labor.
Internal fetal monitoring using catheter tube for precise fetal heart and contraction assessment.
Stress phonocardiography testing to evaluate heart function before and after physical activity.
Doppler phonocardiography for non-invasive measurement of blood flow within the heart.
Biometric identification by capturing heartbeat signatures remotely with high signal quality.
Polygraph examinations measuring cardiovascular, electrodermal, and respiratory physiological processes.
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