Night respiration rate for heart failure monitoring
The invention refers to a monitoring device for monitoring and analyzing physiological signals. The monitoring device comprises a transthoracic impedance measurement unit and an evaluation unit connected to the transthoracic impedance measurement unit. The transthoracic impedance measurement unit is adapted to conduct a transthoracic impedance measurement and to generate a transthoracic impedance signal representing a measured transthoracic impedance at consecutive points in time. The evaluation unit being configured to process the transthoracic impedance signal received from the transthoracic impedance measurement unit and to thus generate a respiration signal and to generate therefrom an evaluation signal reflecting at least a diurnal pattern of the respiration rate.
1. A monitoring device for monitoring and analyzing physiological signals comprising:
a transthoracic impedance measurement unit;
an evaluation unit connected to said transthoracic impedance measurement unit;
said transthoracic impedance measurement unit configured to conduct a transthoracic impedance measurement and to generate a transthoracic impedance signal that represents a measured transthoracic impedance at consecutive points in time;
said evaluation unit configured to process said transthoracic impedance signal received from said transthoracic impedance measurement unit and to thus generate a respiration signal and to generate therefrom an evaluation signal that reflects at least a diurnal pattern of a respiration rate;
a sensing unit configured to process an EGM signal that represents intracardiac myocardial electric potentials and determine therefrom a heart rate signal;
wherein said evaluation unit is configured to perform a trending analysis of multiple different physiological parameters, comprising a heart rate, a heart rate variability and said respiratory rate;
wherein said evaluation unit is configured to determine overall statistics of a respiration rate signal; and,
wherein said evaluation unit is configured to determine a composite score from said multiple different physiological parameters; wherein said evaluation unit is configured to determine said composite score as follows:
CS= a *rRR+ b /dRR+ c *rHR+ d /HRV,
where a, b, c, and d are predefined non-negative coefficients, rRR is a resting respiration rate, dRR is a difference between day and night respiration rates, rHR is a resting heart rate, and HRV is an index of 24-hour heart rate variability.
2. The monitoring device of claim 1 wherein said evaluation unit is configured to detect an increase of a night respiration rate of a patient, and/or decrease of a daytime respiration rate of the patient, and/or decrease of a circadian variability of the respiration rate and to generate an alert signal upon detection of one or more of said increases or decreases.
3. The monitoring device of claim 1 further comprising:
a metal can;
wherein said transthoracic impedance measurement unit is connected or can be connected to a bipolar ventricular electrode lead having a tip electrode at its distal end and a ring electrode close to said tip electrode; and,
wherein said transthoracic impedance measurement unit is configured to inject a current between said ring electrode and said metal can, and to measure a voltage between said tip electrode and said metal can.
4. The monitoring device of claim 3 wherein said transthoracic impedance measurement unit is configured to calculate an impedance as a ratio between a measured voltage and an injected current.
5. The monitoring device of claim 3 wherein said transthoracic impedance measurement unit is configured to measure an impedance signal with a sampling frequency of at least 8 Hz.
6. The monitoring device of claim 3 wherein said transthoracic impedance measurement unit comprises:
a constant current source or a constant voltage source having current feed terminals that are connected or can be connected to electrodes for intracorporal placement and that is configured to generate measuring current pulses having a constant current strength or a constant voltage, respectively, configured to cause the current to be fed through a body via intracorporally placed electrodes;
a measuring unit configured to measure a voltage that corresponds to the current fed through the body by said constant current source or a current strength of the current fed through the body by said constant voltage source, respectively, to determine an impedance value for each measuring current pulse; and,
an impedance value determination unit that is connected to said constant current source or said constant voltage source and the measuring unit.
7. The monitoring device of claim 1 further comprising a low-pass filter and wherein said evaluation unit is configured to process an impedance signal to remove high frequency cardiac components with the low-pass filter, to obtain the respiration signal.
8. The monitoring device of claim 1 wherein said evaluation unit is configured to process an impedance signal to determine a peak-to-peak interval of the respiration signal derived from an intrathoracic impedance signal that is a respiration cycle length.
9. The monitoring device of claim 1 wherein said evaluation unit is configured to process an impedance signal to determine an inflection at an end of expiration and a start of inspiration to determine a respiration cycle length of the respiration signal derived from an intrathoracic impedance signal.
10. The monitoring device of claim 1 further comprising a memory that is configured to store signals and/or data generated by said evaluation unit to further process.
11. The monitoring device of claim 10 further comprising a telemetry unit that is configured for wireless transmission of data, wherein said monitoring device is configured to routinely transmit signals and/or data generated by said evaluation unit to a remote server.
12. The monitoring device of claim 1 wherein said evaluation unit is configured to determine separate day and night statistics of a measured respiration rate with user-programmable daytime and night time settings.
13. The monitoring device of claim 1 where dRR is an index of 24-hour respiration rate variability.
14. The monitoring device of claim 1 wherein said evaluation unit is configured to generate an alert signal if the composite score exceeds a predefined threshold value, due to either an increase of rRR, or an increase of rHR, or a decrease of dRR, or a decrease of HRV, or their combinations.
15. A monitoring device for monitoring and analyzing physiological signals comprising:
a transthoracic impedance measurement unit;
an evaluation unit connected to said transthoracic impedance measurement unit;
said transthoracic impedance measurement unit configured to conduct a transthoracic impedance measurement and to generate a transthoracic impedance signal that represents a measured transthoracic impedance at consecutive points in time;
said evaluation unit configured to process said transthoracic impedance signal received from said transthoracic impedance measurement unit and to thus generate a respiration signal and to generate therefrom an evaluation signal that reflects at least a diurnal pattern of a respiration rate;
wherein said evaluation unit is configured to determine a composite score from multiple different physiological parameters; and,
wherein said evaluation unit is configured to determine said composite score as follows:
CS= a *rRR+ b /dRR+ c *rHR+ d /HRV,
where a, b, c, and d are predefined non-negative coefficients, rRR is a resting respiration rate, dRR is a difference between day and night respiration rates, rHR is a resting heart rate, and HRV is an index of 24-hour heart rate variability.