High sensitivity noise immune stethoscope

• US 9,078,571 B2
• Filed: 08/08/2012
• Issued: 07/14/2015
• Est. Priority Date: 11/15/2005
• Status: Active Grant

• Current Assignee: Active Signal Technologies, Inc
• Original Assignee: Active Signal Technologies, Inc
• Inventors: Bridger, Keith, Cooke, Arthur V., Kohlhafer, Dennis J., Lutian, Joseph J., Sewell, John M., Strite, Richard E.
• Primary Examiner(s): Paul, Disler
• Application Number:
  US13/569,835
• Publication Number:
  US 20120302920A1
• Time in Patent Office: 1,070 Days
• Field of Search: 381/67, 381/56, 600/528, 600/586
• US Class Current: 1/1
• CPC Class Codes: A61B 7/04 Electric stethoscopes microphones, acoustic transducers therefor H04R

Abstract

A physiological sensing stethoscope suitable for use in high-noise environments is disclosed. The stethoscope is designed to be substantially matched to the mechanical impedance of monitored physiological activity and substantially mismatched to the mechanical impedance of air-coupled acoustic activity. One embodiment of the stethoscope utilizes a passive acoustic system. Another embodiment utilizes an active Doppler system. The passive and active systems can be combined in one stethoscope enabling switching from a passive mode to an active mode suitable for use in very high-noise environments. The stethoscope is suitable for use in environments having an ambient background noise of 100 dBA and higher. The passive includes a head having a housing, a flexural disc mounted with the housing, and an electromechanical stack positioned between the housing and the flexural disc in contact with the skin of a patient. The active system detects Doppler shifts using a high-frequency transmitter and receiver.

Claims

1. A stethoscope, comprising:

a housing;

a passive system incorporated into the housing, the passive system comprising an acoustic transducer;

an active system incorporated into the housing, the active system comprising a transmitter and a receiver, wherein the transmitter generates high frequency signals which are reflected from an object thereby creating reflected high frequency signals having a frequency shift dependent on the motion of the object, and wherein the receiver detects the reflected high frequency signals and converts the high frequency signal into an electrical signal; and

a switch in communication with the passive system and the active system, the switch able to select the passive system or active system.

2. The stethoscope of claim 1, wherein the acoustic transducer is an electromechanical stack.

3. The stethoscope of claim 1, wherein the acoustic transducer comprises at least one of piezoelectric lead zirconate titanate, quartz crystal, lithium niobates, barium titanate, lead titanate, meta-lead niobate, lead magnesium niobate, polyvinylidene di-fluoride, and/or Terfenol-D.

4. The stethoscope of claim 1, wherein the passive system is capable of detecting breathing and heartbeat of a patient with ambient noise levels above 85 dBA.

5. The stethoscope of claim 1, wherein the active system is capable of detecting breathing and heartbeat of a patient at ambient noise levels greater than 95 dBA.

6. The stethoscope of claim 1, wherein the active system is capable of detecting breathing and heartbeat of a patient at ambient noise levels up to at least 110 dBA.

7. The stethoscope of claim 1, wherein the switch is manually operable.

8. The stethoscope of claim 1, wherein the housing has a forward side and a rear side, wherein the passive system and active system are both oriented to receive input from the forward side.

9. The stethoscope of claim 1, further comprising an electronics box including a power supply, control logic, an audio switching circuit, a power amplifier and the switch.

10. A stethoscope capable of use in a high amplitude ambient noise environment, comprising:

a housing having a face;

an active system incorporated into the housing, the active system comprising a transmitter and a receiver adjacent to each other in the housing structured and arranged to send and receive ultrasonic signals through the face of the housing to and from a patient exposed to the high amplitude ambient noise environment; and

a signal conditioner for reducing or eliminating unwanted signals selected from the high amplitude ambient noise and/or other spurious signals.

11. The stethoscope of claim 10, wherein the signal conditioner comprises a front end which receives the ultrasonic signals from the patient and wherein the front end comprises a demodulator.

12. The stethoscope of claim 11, wherein the ultrasonic signals are of a selected frequency and the demodulator comprises a bandpass filter set to pass only the ultrasonic signals within +/−

1.0 percent of the selected frequency of the ultrasonic signals.

13. The stethoscope of claim 11, further comprising a bandpass filter following the demodulator which excludes demodulated signals outside an audible range.

14. The stethoscope of claim 13, wherein the audible range is restricted to about 40 Hz to about 500 Hz.

15. The stethoscope of claim 13, further comprising an amplifier to strengthen the demodulated and filtered signal and a user adjusted gain control.

16. A method for detecting anatomical structure motion in a patient in a high amplitude ambient noise environment comprising:

transmitting a high frequency signal into the patient;

receiving a reflected signal from the patient having a frequency shift dependent upon motion of the anatomical structure;

demodulating the reflected signal;

filtering the demodulated signal; and

transmitting the filtered and demodulated signal to an earpiece.

17. The method of claim 16, further comprising amplifying the demodulated and filtered signal prior to the transmission to the earpiece.

18. The method of claim 17, further comprising adjusting the gain of the amplified signal prior to the transmission to the earpiece.