US 11,998,303 B2
Sensing respiration parameters based on an impedance signal
Shantanu Sarkar, Roseville, MN (US); Eric M. Christensen, Gilbert, AZ (US); Deborah Ann Jaye, Lino Lakes, MN (US); Niranjan Chakravarthy, Singapore (SG); Geert Morren, Vissenaken (BE); and Jerry D. Reiland, Coon Rapids, MN (US)
Assigned to Medtronic, Inc., Minneapolis, MN (US)
Filed by Medtronic, Inc., Minneapolis, MN (US)
Filed on Jun. 24, 2019, as Appl. No. 16/450,250.
Prior Publication US 2020/0397308 A1, Dec. 24, 2020
Int. Cl. A61B 5/0205 (2006.01); A61B 5/00 (2006.01); A61B 5/11 (2006.01); A61B 5/364 (2021.01); A61B 5/024 (2006.01); A61B 5/08 (2006.01)
CPC A61B 5/0205 (2013.01) [A61B 5/1118 (2013.01); A61B 5/364 (2021.01); A61B 5/4561 (2013.01); A61B 5/024 (2013.01); A61B 5/0809 (2013.01); A61B 5/0816 (2013.01); A61B 2562/0204 (2013.01)] 13 Claims
OG exemplary drawing
 
1. A method for operating a medical device of a medical device system and processing circuitry of the medical device system, wherein the method comprises:
performing, by the medical device comprising a housing and a plurality of electrodes, an impedance measurement to collect a first set of impedance values over a period of time, wherein the first set of impedance values is indicative of a respiration pattern of a patient, wherein each electrode of the plurality of electrodes is located on the housing, and wherein the housing is configured to be implanted underneath the skin of the patient;
calculating, by the processing circuitry, a mean impedance value of the first set of impedance values;
subtracting, by the processing circuitry, from each impedance value of the first set of impedance values, the mean impedance value to obtain a second set of impedance values;
calculating, by the processing circuitry, a slope value corresponding to each impedance value of the first set of impedance values, wherein the slope value corresponding to each impedance value of the first set of impedance values comprises a difference between an impedance value preceding the respective impedance value of the first set of impedance values and an impedance value following the respective impedance value of the first set of impedance values, wherein a set of slope values includes the slope value corresponding to each impedance value of the first set of impedance values;
identifying, by the processing circuitry, a set of positive zero crossings based on the first set of impedance values, the second set of impedance values, and the set of slope values, wherein identifying the set of positive zero crossings comprises:
identifying, in the second set of impedance values, a first set of pairs of consecutive impedance values each corresponding to a positive zero crossing of the set of positive zero crossings; and
determining, for each pair of the first set of pairs, whether a slope value of the set of slope values corresponding to the pair of impedance values is greater than a positive threshold slope value, wherein the positive threshold slope value is greater than zero, wherein the positive threshold slope value is set at a first value when a positive zero crossing of the set of positive zero crossings is identified, and wherein the positive threshold slope value is decreased from the first value while remaining greater than zero between the positive zero crossing and a subsequent positive zero crossing of the set of positive zero crossings;
determining, by the processing circuitry and based on the set of positive zero crossings, a first set of respiration intervals, wherein each respiration interval of the first set of respiration intervals corresponds to a respective full respiratory cycle within the respiration pattern;
identifying, by the processing circuitry, a set of negative zero crossings based on the first set of impedance values, the second set of impedance values, and the set of slope values, wherein identifying the set of negative zero crossings comprises:
identifying, in the second set of impedance values, a second set of pairs of consecutive impedance values each corresponding to a negative zero crossing of the set of negative zero crossings; and
determining, for each pair of the second set of pairs, whether a slope value of the set of slope values corresponding to the pair of impedance values is less than a negative threshold slope value, wherein the negative threshold slope value is less than zero, wherein the negative threshold slope value is set at a second value when a negative zero crossing of the set of negative zero crossings is identified, and wherein the negative threshold slope value is increased from the second value while remaining less than zero between the negative zero crossing and a subsequent negative zero crossing of the set of negative zero crossings;
determining, by the processing circuitry and based on the set of negative zero crossings, a second set of respiration intervals, wherein each respiration interval of the second set of respiration intervals corresponds to a respective full respiratory cycle within the respiration pattern;
determining, by the processing circuitry and for the impedance measurement, a value of a respiration metric using both the set of negative zero crossings and the set of positive zero crossings;
determining, by the processing circuitry based on the value of the respiration metric, a status of a patient condition;
outputting, by the processing circuitry to a user device operated by the patient based on determining the status of the patient condition, an alert including a suggestion for the patient to seek medical attention; and
delivering stimulation, by the medical device and to the patient, based at least in part on instructions, processed by the processing circuitry, that were updated based at least in part on the impedance measurement.