Apnea monitoring system

• US 4,580,575 A
• Filed: 10/12/1984
• Issued: 04/08/1986
• Est. Priority Date: 06/14/1982
• Status: Expired due to Term

• Current Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Original Assignee: Aequitron Medical, Inc. (Medtronic Plc)
• Inventors: Stasz, Peter, Birnbaum, Michael R.
• Primary Examiner(s): Howell, Kyle L.
• Assistant Examiner(s): Hanley, John C.
• Application Number:
  US06/660,458
• Time in Patent Office: 543 Days
• Field of Search: 128/671, 128/716, 128/721, 128/722, 128/723, 128/708, 128/702, 128/696, 128/706
• US Class Current: 600/484
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0809 by impedance pneumography
• CPC Class Codes: A61B 5/4818 Sleep apnoea

Abstract

Apparatus for monitoring respiration and heartbeat and for processing electrical signals representative thereof, including circuits for developing a phase-shifted and amplitude-offset respiration signal for comparison with an original respiration signal for compensating for signal drift, and circuits for logically combining signals representative of the presence of respiration and heartbeat for eliminating certain false indications which may occur when only heartbeat exists.

Claims

1. An apparatus for monitoring patient respiration and heartbeat, comprising

(a) sensor means adapted for coupling to said patient for sensing composite electrical signals representative of said patient heartbeat and respiration;

(b) oscillator means for generating a carrier frequency, coupled to said sensor means;

(c) detector means for receiving and detecting said heartbeat and respiration signals, coupled to said sensor means and said oscillator means;

(d) heartbeat detection circuit, coupled to said detector means, said heartbeat detection circuit having means for developing a first single signal responsive to each detected heartbeat;

including a first circuit for generating a detected heartbeat signal and for rectifying said signal, a second circuit for receiving said rectified signal and generating a time-decaying signal therefrom, said time-decaying signal having a greater time duration than said detected heartbeat signal, and a circuit means for receiving said time-decaying signal and generating an intergrated pulse signal therefrom, and a comparator circuit means for receiving said time-decaying signal and said integrated pulse signal and generating said first single signal when said time-decaying signal is greater than said integrated pulse signal;

(e) respiration detection circuit, coupled to said detector means, said respiration detection circuit having means for developing a second single signal responsive to each detected respiration;

including a first integrator circuit for developing a first integrated respiration signal and a second integrator circuit for developing a second integrated respiration signal time delayed relative to said first integrated respiration signal, and a circuit for receiving said first and second integrated respiration signals and for developing said second single signal when said first integrated respiration signal is greater than said second integrated respiration signal; and

(f) heartbeat alarm circuit coupled to receive said first single signal responsive to each detected heartbeat, said heartbeat alarm circuit having means for presetting a minimum and maximum heartbeat rate and having means for developing a received heartbeat rate signal responsive to said first single signals, and having means for generating an alarm when said received heartbeat rate signal falls below said minimum or above said maximum preset heartbeat rate.

2. An apparatus for monitoring patient respiration and heartbeat and for generating alarm signals under predetermined conditions of heartbeat and respiration, comprising

(a) sensor means adapted for coupling to said patient for sensing composite electrical signals representative of said patient heartbeat and respiration;

(b) oscillator means for generating a carrier frequency, coupled to said sensor means;

(c) detector means for receiving and detecting said heartbeat and respiration signals, coupled to said sensor means and said oscillator means;

(d) heartbeat detection circuit, coupled to said detector means, said heartbeat detection circuit having means for developing a first single signal responsive to each detected heartbeat;

including means for developing a signal representative of said heartbeat, means for rectifying said representative signal, means for time decaying said rectified representative signal over a time duration longer than said signal representative of said heartbeat and for developing a blanking signal, means for integrating said blanking signal to develop an integrated pulse signal, means for receiving and comparing said blanking signal and said integrated pulse signal and for developing said first single signal during the time when said blanking signal is greater than said integrated pulse signal;

(e) respiration detection circuit, coupled to said detector means, said respiration detection circuit having means for developing a second single signal responsive to each detected respiration;

including means for developing a signal representative of said detected respiration, first means for integrating said representative signal to develop a first integrated signal, second means for integrating said representative signal to develop a second integrated signal, said second integrated signal being time delayed relative to said first integrated signal, means for comparing said first integrated signal and said second integrated signal and for developing said second single signal when said first integrated signal is greater than said second integrated signal;

(f) heartbeat alarm circuit coupled to receive said single signal responsive to each detected heartbeat, said heartbeat alarm circuit having means for presetting a minimum and maximum heartbeat rate and having means for developing a first heartbeat rate signal responsive to said first single signals, and having means for generating an alarm when said first heartbeat rate signal falls outside either of said minimum or said maximum preset heartbeat rate; and

(g) respiration alarm circuit coupled to receive said single second signal, said respiration alarm circuit having means for developing a respiration rate signal responsive to said second single signals, and having means for comparing said respiration rate signal with said heartbeat rate signal, and having means for generating an apnea alarm when said heartbeat rate signal and said respiration rate signal are substantially equal.

3. The apparatus of claim 2, further comprising timer means coupled to said respiration alarm circuit, for generating a further alarm signal a predetermined time after said apnea alarm has been generated.

4. An apparatus for monitoring signals representative of patient respiration and heartbeat and for processing said signals to generate alarm signals under predetermined conditions of respiration and heartbeat, comprising

(a) sensor means adapted for coupling to said patient for generating composite electrical signals representative of said patient heartbeat and respiration;

(b) first detector means coupled to said sensor for receiving said sensor composite signals and for detecting and separating therefrom signals representative of heartbeat, and for generating a single first signal for each detected heartbeat signal comprising means for rectifying said detected heartbeat signal and for generating a time-decaying signal from said rectified heartbeat signal, said time-decaying signal extending for a longer time duration than said heartbeat signal;

said means for generating a single first signal further comprising means for integrating said time-decaying signal and means for comparing said time-decaying signal and said integrated time-decaying signal and for generating said single first signal during the time period when said time-decaying signal is greater than said integrated time-decaying signal;

(c) second detector means coupled to said sensor for receiving said sensor composite signals and for detecting and separating therefrom signals representative of patient respiration, and for generating a single second signal for each detected respiration signal, comprising first integrating means for generating a first integrated respiration signal and second integrating means for generating a second integrated respiration signal, said second integrated respiration signal being time delayed relative to said first integrated respiration signal;

said means for generating a single second signal further comprising means for comparing said first and second integrated respiration signals and for generating said single second signal during the time period when said first integrated respiration signal is greater than said second integrated respiration signal;

(d) first rate detection circuit means coupled to receive said first signal, for generating a first rate signal representative of the time rate of receiving said first signal;

(e) second rate detection circuit means coupled to receive said second rate signal, for generating a second rate signal representative of the time rate of receiving said second signal; and

(f) comparison means coupled to receive said first rate signal and said second rate signal and for generating an apnea signal when said first and second rate signals are equal within predetermined limits;

(g) EKG alarm circuit means coupled to receive said first detector means first signal, for generating an EKG alarm when the repetition rate of said first signal is outside of a preselected range of repetition rates; and

(h) respiration alarm circuit means coupled to receive said apnea signal from said comparison means, for generating an apnea alarm signal when said apnea signal is present for greater than a predetermined time duration.

5. The apparatus of claim 4, wherein said sensor means further comprises an oscillator means for generating a fixed frequency signal as a carrier for said electrical signals representative of patient respiration.

6. The apparatus of claim 4, wherein said EKG alarm circuit means further comprises a first comparison means for comparing the repetition rate of said first signal with a first predetermined signal representative of a low repetition rate, and for generating an EKG alarm when said first signal repetition rate falls below said low repetition rate.

7. The apparatus of claim 6, wherein said EKG alarm circuit further comprises a second comparison means for comparing said first signal repetition rate with a second predetermined signal representative of a high repetition rate, and for generating an EKG alarm when said first signal repetition rate exceeds said high repetition rate.

8. The apparatus of claim 5, wherein said first detector means further comprises means for filtering said oscillator signal from said composite signals.

9. The apparatus of claim 8, wherein said second detector means further comprises means for filtering said oscillator signal from said composite signals.

10. The apparatus of claim 9, further comprising EKG alarm circuit means coupled to receive said first detector means first signal, for generating an EKG alarm when said first signal repetition rate falls outside a preselected range of repetition rates.

11. The apparatus of claim 10, further comprising respiration alarm circuit means coupled to receive said apnea signal from said comparison means, for generating an apnea alarm signal when said apnea signal exceeds a predetermined time duration.

12. The apparatus of claim 11, wherein said EKG alarm circuit means further comprises a first comparison means for comparing the repetition rate of said first signal with a first predetermined signal representative of a low repetition rate, and for generating an EKG alarm when said first signal repetition rate falls below said low repetition rate.

13. The apparatus of claim 12, wherein said EKG alarm circuit further comprises a second comparison means for comparing the repetition rate of said first signal with a second predetermined signal representative of a high repetition rate, and for generating an EKG alarm when said first signal repetition rate exceeds said high repetition rate.