Cardiac and pulmonary physiological analysis via intracardiac measurements with a single sensor

• US 5,003,976 A
• Filed: 09/28/1988
• Issued: 04/02/1991
• Est. Priority Date: 09/28/1987
• Status: Expired due to Term

• Current Assignee: Eckhard Alt
• Original Assignee: Eckhard Alt
• Inventors: Alt, Eckhard
• Primary Examiner(s): Cohen, Lee S.
• Assistant Examiner(s): SCHAETZLE, KENNEDY
• Application Number:
  US07/250,155
• Time in Patent Office: 916 Days
• Field of Search: 128/671, 128/672, 128/670, 128/723, 128/734, 128/419 P, 128/419 PG
• US Class Current: 607/18
• CPC Class Codes: A61N 1/36521 the parameter being derived from measurement of an electrical impedance
• CPC Class Codes: A61N 1/36571 controlled by blood flow rate, e.g. blood velocity or cardiac output

Abstract

Physiological activity of a patient is detected and analyzed by means of a single sensor situated in the vascular system of the patient. Pulmonary activity is derived from analysis of changes in cardiac activity, such as sensed from blood flow, pressure or volume changes, measured in a preferred embodiment as impedance change within the right heart. Pulmonary activity is separated from cardiac activity implicit in such changes by filtering lower and higher frequency components. The separated signals are processed to derive control signals for stimulating the heartbeat in a pacemaker system, preferably by a single sensor-stimulator electrode implanted within the right heart. Thus, a single functional parameter, namely intra-cardiac impedance, varying both with the intrathoracic pressure fluctuations following respiration and with cardiac contraction is representative of the pulmonary activity and of the cardiac activity. Resulting derived sub-signals then provide information regarding cardiac and pulmonary activity and are used to monitor the patient'"'"'s condition and control variably the rate of a cardiac pacemaker.

Claims

1. Electronic medical instrumentation for determining a plurality of physiological parameters related to a patient'"'"'s condition, comprising in combination:

a single sensor adapted to be located wholly within the heart including sensor means to detect a signal varying with characteristics of the blood with corresponding signal processing means for producing from the signal detected at said sensor a variable signal including information representative of a plurality of physiological parameters of the patient related to cardiac blood flow parameters, and

physiological activity detection means for processing the variable signal including signal processing means for separating said variable signal into subsignals respectively representative of the plurality of the patient'"'"'s physiological parameters presented in said variable signal derived from blood characteristics at the in-situ position of the sensor in the heart.

2. The instrumentation of claim 1 wherein said signal processing means for separating said variable signal into subsignals further comprises separate pulmonary and cardiac activity analyzing means responsive to produce respective ones of said subsignals from said variable signal.

3. The instrumentation of claim 1 further in combination with:

a heart pacemaker having means for generating heart pacing pulses at said single sensor, and

control means in said pacemaker for producing heart pacing pulses responsive to changes derived as a function of said plurality of physiological parameters including parameters representative of cardiac and pulmonary activity of a patient separated as said subsignals.

4. The instrumentation of claim 3 wherein the signal processing means for producing the variable signal further comprises:

means for generating a periodic electrical interrogation signal at said single sensor of low enough energy that the heart is not paced thereby, which interrogation signal in kind produces said variable signal in response to and varying with cardiac and pulmonary activity, and

the signal processing means for separating the variable signal into subsignals further comprises means for producing separate said subsignals representative of pulmonary and cardiac activity of the patient.

5. The instrumentation of claim 3 wherein the corresponding means for producing the variable signal derives at the sensor means signals representative of cardiac and pulmonary activity in response to changes of pressure in the patient'"'"'s cardiovascular system.

6. The instrumentation of claim 3 wherein the sensor means detects said variable signal responsive to the changes in the volume of the patient'"'"'s blood in the cardiovascular system.

7. The instrumentation of claim 1 wherein the sensor means comprises a bipolar impedance detection electrode set adapted to be located in the patient'"'"'s cardiovascular system.

8. The instrumentation of claim 3 wherein the sensor means detects changes in the flow of blood in the patient'"'"'s cardiovascular system.

9. Electronic medical instrumentation for determining a plurality of physiological parameters related to a patient'"'"'s heart activity, comprising in combination,

detection means comprising measuring element means adapted to be located within a patient'"'"'s heart with accompanying measuring means for producing a variable electrical signal containing one or more physiological parameters within the patient'"'"'s heart varying with blood characteristics to include signal information responsive to both the intrathoracic pressure fluctuations acting on the heart from the patient'"'"'s breathing and the internal heart activity,

and separate signal processing channels including separation means for deriving from said variable electrical signal two subsignals respectively representative of the patient'"'"'s breathing and internal heart activity for use in monitoring the patient'"'"'s condition.

10. The instrumentation defined in claim 9 adapted to control heartbeat rate further comprising:

said measuring element means comprising sensor electrode means adapted to be implanted in the right heart of the patient,

a heart pacer for producing stimulation signals at said sensor electrode means,

and further including heartbeat rate control means responsive to control by signals detected at said sensor electrode means from variations in blood characteristics for controlling the heartbeat rate in response to both said breathing and heart activity subsignals with impulses to said sensor electrode means, whereby the instrumentation both stimulates the heart and senses physiological activity within the heart at said sensor electrode means.

11. The instrumentation defined in claim 10 wherein said detection means further comprises impedance measuring means responsive primarily to impedance changes detechable at said sensor electrode means resulting from both pulmonary activity and cardiac activity of the patient.

12. The instrumentation defined in claim 9 wherein said separation means further comprises, filtering means for dividing the variable signal as measured wholly within the heart into said two sub-signals respectively processed by the two processing channels comprising a low frequency filter passing signals corresponding to intrathoric pressure fluctuations at the patient'"'"'s breathing rate and a high frequency filter passing periodic signals of cardiac activity corresponding to the patient'"'"'s cardiac activity.

13. In a cardiac heartbeat pacing system, the improvement comprising in combination,

electronic heart stimulating means for inducing pacing pulses, a bipolar electrode adatpted to be implanted within the heart of a patient to receive the pacing pulses for pacing a heart,

measuring means for measuring a variable wholly within the heart representative of at least one physiological factor of the patient detected at said electrode in response to periodic pulmonary activity of the patient and deriving a signal of a frequency and amplitude that represents breathing rate and tidal volume and which does not interfere with pulses at the bipolar electrode for pacing the heart of the patient, and

means for modulating the signal from the pacing pulses frequency as a function of the pulmonary activity measured by the measuring means.

14. A system as defined in claim 13 wherein said measuring means includes impedance sensing means for distinguishing two said physiological factors from periodically recurring impedance changes relating to both cardiac and pulmonary activity, and band pass filter means for isolating the respective periodically recurring changes of the measured variable wholly within the heart into two differing frequency ranges by passing the respective two signals through band pass filters thereby to derive separate non-interfering signals for cardiac and pulmonary activity.

15. In a cardiac pacing method for stimulating a heartbeat with an electronic stimulation signal induced in a stimulation electrode implanted in the heart of a patient, the improvement comprising in combination the steps of, deriving a variable signal representative of a parameter exhibited wholly within the heart from said electrode with which the stimulation signal does not interfere, establishing a control signal from a restricted range of lower frequency components of said variable signal excluding higher frequency heartbeat components for the patient being monitored representive of a physiological respiratory parameter of the patient critical to pacing, and controlling the stimulation signal as a function of the control signal.

16. The method of control of a heartbeat pacing system having a bipolar electrode implanted in a patient'"'"'s heart and means for producing periodic electronic stimulation signals thereto to induce heartbeats, comprising the steps of:

measuring the impedance at a position wholly within the heart by means of the implanted bipolar electrode to produce a variable intracardiac impedance signal indicative of dynamic instantateous physiological functioning of the lungs and heart, and

modulating the periodic stimulation signals with a pulmonary function derived from the variable impedance signal.

17. The method of monitoring physiological functioning of the lungs and the heart during variations of workload exercise in a patient, comprising the steps of:

developing characteristics of blood detected at an in-situ electrode within the heart in response to a variable signal having two periodic signal components respectively signifying the cardiac activity and the pulmonary activity of the patient, and

separating the two periodic signal components for processing in separate channels responsive respectively to a lower frequency pulmonary activity and a higher frequency cardiac activity with said channels having a bandwith sufficient to identify modulations of rate and amplitude of the respective lower and higher frequency signal components for monitoring respectively pulmonary and cardiac activity.

18. The method of monitoring a patient'"'"'s cardiac activity comprising the steps of detecting at only two separated positions within the heart of a patient a single variable impedance signal carrying separable signal components of two differing periodic frequency ranges respectively in a higher heartbeat rate range and a lower respiratory rate range, and monitoring respective signal components to obtain information pertaining to pulmonary and cardiac activity from frequency and amplitude variations of the respective two impedance signal components.

19. The method of monitoring cardiac conditions comprising the steps of determinig ventilatory parameters of a patient from an analysis of the influence of periodic intrathoracic pressure fluctuations in a signal detected by a detector electrode structure implanted wholly within the heart by a substep of isolating signal components in a restricted frequency range including the pulmonary rate and excluding the heartbeat rate with low pass filter means to derive a signal representative of said ventilatory parameters.

20. The method defined in claim 19, further providing for the step of detecting the thoracic pressure changes during ventilation of a patient comprising the substeps of implanting said detector electrode structure within the right ventricle and producing said signal that varies with the blood suction effect of pulmonary activity.

21. The method of claim 19 comprising the further steps of commonly processing in a signal processing channel a first said signal detected by said detector electrode structure representative of both instantaneous dynamic pulmonary and cardiac activity of a patient having the characteristic of insignificant reduction of the pulmonary signal component with changes in cardiac activity obtained from monitoring a single cardiac responsive parameter related to cardiac activity obtained from said electrode structure and isolating from the first said signal said pulmonary activity to produce signal components in a restricted frequency range.

22. The method of operating a stimulus electrode with bipolar electrode structure implanted wholly within the heart to control a heartbeat pulse rate comprising the steps of operating the electrode structure in a concurrent mode as a detector of intracardiac impedance of a pulmonary parameter wholly within the heart that is critical to the heartbeat pulse rate, and controlling heartbeat pulse rate by stimulus to the electrode as a function of the pulmonary parameter.

23. A heart pacemaker comprising in combination,

pulse generator means for generating heart pacing pulses,

a common sensor and pacing electrode adapted for location wholly within the heart and sensing means coupled thereto for deriving from parameters appearing at said sensor electrode wholly within the heart of a patient a signal modulated with a multiplicity of physiological functional parameters related to the patient'"'"'s condition.

processing means responsive to said signal to provide sub-signal components representative of said physiological parameters for respectively pulmonary activity and cardiac activity, and

control means for changing the rate of the heart pacing pulses in response to the detected pulmonary and cardiac activity sub-signal components.

24. A heart pacemaker as defined in claim 23, wherein said common sensor and said sensing means for deriving the signal comprises:

means for generating an electrical measurement signal of low energy unable to pace the heart to derive said signal,

means for transmitting the measurement signal and pacing signal to the pacing electrode over a common communication channel,

means coupled to said channel for receiving, detecting, and analizying the single signal to derive signals representative of dynamic changes in pulmonary and cardiac activity, and

means for varying the pacing pulse rate in response to said dynamic changes.

25. A heart pacemaker as defined in claim 23 having a pacing electrode positioned in a patient'"'"'s right heart, wherein said means for deriving a single signal comprises:

pressure sensing means situated in the cardiovascular system of a patient for producing said single signal, and

means for detecting said physiological parameters from monitoring the pressure sensed by said pressure sensing means.

26. A heart pacemaker as defined in claim 23 wherein said means for deriving a single signal comprises:

blood flow sensing means adapted for location in a patient'"'"'s cardiovascular system, and

means for detecting said physiological parameters from monitoring blood flow sensed by said blood flow sensing means.

27. A heart pacemaker system including pulse generator means for generating heart pacing pulses, comprising in combination, blood flow sensing means adapted to be located wholly within the heart coupled with means for deriving from a patient a signal modulated with a multiplicity of physiological functional parameters relating to the patient'"'"'s condition, detection means responsive to said signal to provide sub-signal components representative of said physiological parameters for cardiovascular activity, and control means for changing the rate of the pacing pulses in response to the detected cardiovascular activity sub-signal components.