Determining an efficacy of a treatment program

1 . A medical device system comprising:

an implantable medical device comprising one or more sensors, wherein the implantable medical device is configured to be implanted underneath a skin of a patient so that the implantable medical device and the one or more sensors occupy a desired orientation over a period of time greater than seven days, the one or more sensors including:

a set of electrodes located on a first major surface of the implantable medical device opposite a second major surface of the implantable medical device, wherein the first major surface faces target tissue of the patient when the implantable medical device occupies the desired orientation over the period of time greater than seven days; and

sensing circuitry configured to generate, based on a physiological signal sensed from the target tissue of the patient via the set of electrodes when the implantable medical device occupies the desired orientation over the period of time greater than seven days, an electrical signal that indicates a parameter of the patient over the period of time greater than seven days; and

processing circuitry configured to:

receive data indicating a reference time indicative of beginning administration of a treatment;

determine a plurality of parameter values of the parameter based on a portion of the electrical signal corresponding to a period of time including the reference time;

identify, based on a first set of parameter values of the plurality of parameter values occurring before the reference time, a reference parameter value;

calculate, based on a second set of parameter values of the plurality of parameter values occurring after the reference time and based on the reference parameter value, a parameter change value; and

determine, based on the parameter change value, whether an improvement or a worsening of the patient has occurred responsive to the treatment.

2 . The medical device system of claim 1 , wherein the processing circuitry is configured to:

identify a set of difference values, wherein each difference value of the set of difference values represents a difference between the respective parameter value of the second set of parameter values and the reference parameter value, wherein the second set of parameter values occur after the reference time;

determine a sum of the set of difference values;

determine a delta value which represents a difference between the reference parameter value and a target parameter value; and

calculate the parameter change value by determining a ratio of the sum of the set of difference values to the delta value.

3 . The medical device system of claim 1 , wherein to identify the reference parameter value, the processing circuitry is configured to calculate the reference parameter value to be a mean of the first set of parameter values.

4 . The medical device system of claim 1 , wherein to identify the reference parameter value, the processing circuitry is configured to calculate the reference parameter value to be a median of the first set of parameter values or another statistical representation of the first set of parameter values.

5 . The medical device system of claim 1 , wherein to determine whether the improvement or the worsening of the patient has occurred, the processing circuitry is configured to:

compare the parameter change value with a first threshold parameter change value and a second threshold parameter change value;

determine that the improvement of the patient has occurred when the parameter change value is greater than the first threshold parameter change value;

determine that the worsening of the patient has occurred when the parameter change value is less than the second threshold parameter change value; and

determine that neither the improvement nor the worsening of the patient has occurred when the parameter change value is greater than or equal to the second threshold parameter change value and less than or equal to the first threshold parameter change value.

6 . The medical device system of claim 5 , wherein the first threshold parameter change value is within a range from 0.5 to 0.9.

7 . The medical device system of claim 6 , wherein the first threshold parameter change value is 0.7.

8 . The medical device system of claim 1 , wherein the plurality of parameter values represents a sequence of parameter values, and wherein the processing circuitry is configured to select the second set of parameter values to be consecutive parameter values of the sequence of parameter values starting a predetermined number of parameter values after the reference time.

9 . The medical device system of claim 8 , wherein the second set of parameter values comprises three consecutive parameter values, and wherein three parameter values separate the second set of parameter values and the reference time.

10 . The medical device system of claim 1 , wherein each parameter value of the plurality of parameter values corresponds to a respective time interval of a sequence of time intervals.

11 . The medical device system of claim 10 , wherein each parameter value of the plurality of parameter values represents a set of parameter value components collected during the respective time interval, and wherein to determine the plurality of parameter values, the processing circuitry is configured to calculate each parameter value of the plurality of parameter values based on the respective set of parameter value components.

12 . The medical device system of claim 10 , wherein a duration defining each time interval of a sequence of time intervals is one day.

13 . The medical device system of claim 1 , wherein a length of the implantable medical device is greater than a depth of the implantable medical device and a width of the implantable medical device is greater than the depth of the implantable medical device to cause, throughout the period of time greater than seven days, the implantable medical device to occupy the desired orientation.

14 . A method comprising:

generating, by sensing circuitry of an implantable medical device comprising one or more sensors including a set of electrodes and the sensing circuitry, an electrical signal based on a physiological signal sensed from target tissue of a patient via the set of electrodes when the implantable medical device occupies a desired orientation over a period of time greater than seven days, wherein the electrical signal indicates a parameter of the patient over the period of time greater than seven days, wherein the implantable medical device is configured to be implanted underneath a skin of the patient so that the implantable medical device and the one or more sensors occupy the desired orientation over the period of time greater than seven days, and wherein the set of electrodes is located on a first major surface of the implantable medical device opposite a second major surface of the implantable medical device, wherein the first major surface faces target tissue of the patient when the implantable medical device occupies the desired orientation over the period of time greater than seven days;

receiving, by processing circuitry of the implantable medical device, data indicating a reference time indicative of beginning administration of a treatment;

determining, by the processing circuitry, a plurality of parameter values of the parameter based on a portion of the electrical signal corresponding to a period of time including the reference time;

identifying, by the processing circuitry based on a first set of parameter values of the plurality of parameter values occurring before the reference time, a reference parameter value;

calculating, by the processing circuitry based on a second set of parameter values of the plurality of parameter values occurring after the reference time and based on the reference parameter value, a parameter change value; and

determining, by the processing circuitry based on the parameter change value, whether an improvement or a worsening of the patient has occurred responsive to the treatment.

15 . The method of claim 14 , further comprising:

identifying, by the processing circuitry a set of difference values, wherein each difference value of the set of difference values represents a difference between the respective parameter value of the second set of parameter values and the reference parameter value, wherein the second set of parameter values occur after the reference time;

determining, by the processing circuitry, a sum of the set of difference values;

determining, by the processing circuitry, a delta value which represents a difference between the reference parameter value and a target parameter value; and

calculating, by the processing circuitry, the parameter change value by determining a ratio of the sum of the set of difference values to the delta value.

16 . The method of claim 14 , wherein identifying the reference parameter value comprises calculating, by the processing circuitry, the reference parameter value to be a mean of the first set of parameter values.

17 . The method of claim 14 , wherein identifying the reference parameter value comprises calculating, by the processing circuitry, the reference parameter value to be a median of the first set of parameter values or another statistical representation of the first set of parameter values.

18 . A non-transitory computer-readable medium comprising instructions for causing one or more processors to:

cause sensing circuitry of an implantable medical device comprising one or more sensors including a set of electrodes and the sensing circuitry to generate an electrical signal based on a physiological signal sensed from target tissue of a patient via the set of electrodes when the implantable medical device occupies a desired orientation over a period of time greater than seven days, wherein the electrical signal indicates a parameter of the patient over the period of time greater than seven days, wherein the implantable medical device is configured to be implanted underneath a skin of the patient so that the implantable medical device and the one or more sensors occupy the desired orientation over the period of time greater than seven days, and wherein the set of electrodes is located on a first major surface of the implantable medical device opposite a second major surface of the implantable medical device, wherein the first major surface faces target tissue of the patient when the implantable medical device occupies the desired orientation over the period of time greater than seven days;

receive data indicating a reference time indicative of beginning administration of a treatment;

determine a plurality of parameter values of the parameter based on a portion of the electrical signal corresponding to a period of time including the reference time;

identify, based on a first set of parameter values of the plurality of parameter values occurring before the reference time, a reference parameter value;

calculate, based on a second set of parameter values of the plurality of parameter values occurring after the reference time and based on the reference parameter value, a parameter change value; and

determine, based on the parameter change value, whether an improvement or a worsening of the patient has occurred responsive to the treatment.