Ultrasonic respiration/convulsion monitoring apparatus and method for its use
First Claim
1. Apparatus for non-contact monitoring of movement of a subject comprising:
- (a) ultrasound source means for generating and transmitting to the abdominal/chest area of a person to be monitored coherent ultrasound whose frequency is controllable by application to said source of a control signal, the transmitted sound wave being reflected from said person to provide a reflected sound wave;
(b) receiver means positioned to receive said reflected sound wave;
(c) phase detector means coupled to said ultrasound source means and to said receiver means and adapted to compare the phase of said reflected sound wave to the phase of said transmitted sound wave and to generate a phase difference signal therefrom;
(d) change detection means coupled to said phase detector means to modify said phase difference signal to generate therefrom a change signal which is proportional to changes in the length of the air path of said transmitted and reflected sound waves between said transmitter means and said receiver means, said change signal thereby exhibiting variations representing the amplitude of respiratory motion when said source means and said receiver means are aimed at the breathing person;
(e) frequency adjusting means coupled to said change detection means to receive said change signal and coupled to said generating means to adjust the frequency of said signal voltage in response to said change signal so as to maintain substantially constant the number of wave lengths of ultrasound in said air path despite changes in the length thereof; and
(f) window/alarm circuit means coupled to said change detector means to receive said change signal for determining whether said variations in said change signal lie within a selected range of values representative of proper respiration for a selected interval of time and for sounding an alarm when said change signal does not lie within said selected range for said selected interval of time.
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Abstract
Apparatus for monitoring respiratory and/or convulsive movements includes a closed loop phase lock system which measures changes in the air path length of continuous wave ultrasound transmitted to and reflected from (the chest/abdomen area of) a subject, and provides an output change signal proportional to changes in air path length caused by respiratory effort of the subject. A window/alarm circuit receives the change signal and triggers an alarm if the change signal remains below a preset lower threshold for a selected time interval, as occurs in apnea. An upper threshold may be set and an alarm triggered if the change signal exceeds the upper threshold for a selected time interval, as occurs in the case of convulsions. The apparatus includes means to provide a signal which follows movement of the subject in an unambiguous manner and which will not trigger an alarm due to extraneous (non-subject) movement. A method of monitoring movement of a subject is provided which includes transmitting continuous wave ultrasound from a source to a subject and receiving the reflected ultrasound. The method includes measuring changes in the air path length of the standing wave and providing an output signal which is proportional to the magnitude of the changes and sounding an alarm when the output signal falls outside a preselected range for a predetermined period of time.
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Citations
19 Claims
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1. Apparatus for non-contact monitoring of movement of a subject comprising:
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(a) ultrasound source means for generating and transmitting to the abdominal/chest area of a person to be monitored coherent ultrasound whose frequency is controllable by application to said source of a control signal, the transmitted sound wave being reflected from said person to provide a reflected sound wave; (b) receiver means positioned to receive said reflected sound wave; (c) phase detector means coupled to said ultrasound source means and to said receiver means and adapted to compare the phase of said reflected sound wave to the phase of said transmitted sound wave and to generate a phase difference signal therefrom; (d) change detection means coupled to said phase detector means to modify said phase difference signal to generate therefrom a change signal which is proportional to changes in the length of the air path of said transmitted and reflected sound waves between said transmitter means and said receiver means, said change signal thereby exhibiting variations representing the amplitude of respiratory motion when said source means and said receiver means are aimed at the breathing person; (e) frequency adjusting means coupled to said change detection means to receive said change signal and coupled to said generating means to adjust the frequency of said signal voltage in response to said change signal so as to maintain substantially constant the number of wave lengths of ultrasound in said air path despite changes in the length thereof; and (f) window/alarm circuit means coupled to said change detector means to receive said change signal for determining whether said variations in said change signal lie within a selected range of values representative of proper respiration for a selected interval of time and for sounding an alarm when said change signal does not lie within said selected range for said selected interval of time. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Apparatus for monitoring movement of a subject comprising:
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(a) generating means for generating a signal voltage of ultrasonic frequency; (b) transmitter means coupled to said generating means to convert said signal voltage for transmission of an ultrasonic sound wave to the abdominal/chest area of a person to be monitored, the transmitted sound wave being reflected from said person to provide a reflected sound wave; (c) receiver means to receive the reflected sound wave; (d) phase detector means coupled to said generating means and to said receiver means to receive input therefrom and to generate a difference signal indicative of the phase difference between the transmitted and reflected sound waves; (e) change detector means comprising an integrator circuit coupled to the output of said phase detector means to receive said difference signal and generate a change signal indicative of transient changes in the phase difference measured by said phase detector means, said change signal being proportional to changes in the length of the air path of said transmitted and reflected sound waves between said transmitter and receiver means, said change signal thereby exhibiting variations representing the amplitude of respiratory motion when said transmitter means and said receiver means are aimed at the breathing person; (f) frequency adjusting means coupled between said integrator circuit and said generating means to adjust the frequency of said signal voltage in response to said change signal so as to maintain substantially constant the number of wave lengths of ultrasound in said air path despite changes in the length thereof whereby said change signal follows movement of said person in an unambiguous manner; and (g) window/alarm circuit means coupled to said change detector means to receive said change signal for determining whether said variations in said change signal lie within a selected range of values representative of proper respiration for a selected interval of time and for sounding an alarm when said change signal does not lie within said selected range for said selected interval of time. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for monitoring movement of a person comprising:
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(a) generating a coherent ultrasonic sound wave and transmitting said sound wave to the chest/abdominal area of a person to be monitored for reflection therefrom to provide a reflected ultrasonic sound wave; (b) receiving said reflected sound wave to define an air path length of the transmitted and reflected untrasonic sound wave; (c) comparing the phase of said transmitted sound wave to the phase of said received reflected sound wave and determining the difference between the respective measured phases; (d) measuring changes in the difference between said respective measured phases to provide a change signal which is proportional to changes in said air path length; (e) adjusting the frequency of the transmitted ultrasonic sound wave in response to said change signal so as to maintain substantially constant the number of wave lengths of ultrasonic sound in said air path length despite changes in the length thereof; (f) establishing a predetermined range of values for said change signal representing normal breathing of said person; (g) monitoring said change signal which represents variations indicative of the amplitude of respiratory movement of said person; (h) comparing the value of the monitored change signal with said predetermined range of values; and (i) sounding an alarm when said change signal lies outside said predetermined range for a selected interval of time.
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Specification