Medical device for fall detection

A method for detecting a patient fall by a medical device, comprising:

• producing an accelerometer signal;
• generating a body posture signal and a body acceleration signal from the accelerometer signal;
• determining that the body posture signal and the body acceleration signal meet fall detection criteria by:
• determining a first body posture vector from the body posture signal at a first time point;
• determining a second body posture vector from the body posture signal at a second time point later than the first time point of the first body posture vector;
• determining a directional change metric correlated to an angle between the first body posture vector and the second body posture vector;
• determining that the directional change metric is greater than a threshold directional change;
• detecting an acceleration signal spike from the body acceleration signal;
• and
• determining that the acceleration signal spike and the second time point are within a fall time window of each other;
• detecting a patient fall in response to the body posture signal and the body acceleration signal meeting the fall detection criteria;
• determining a third body posture vector at a third time point after the second time point;
• determining a directional change metric between the third body posture vector and at least one of the first body posture vector and the second body posture vector;
• determining that the directional change metric meets fall recovery criteria;
• determining a fall recovery time as a time interval from the second time point to the third time point in response to the directional change metric meeting the fall recovery criteria;
• determining at least one of a trend in a frequency of fall detections and a trend in fall recovery time durations in response to detecting the patient fall;
• transmitting the determined trend;
• receiving a first truth signal transmitted from another device indicating that the detected patient fall is a falsely detected patient fall;
• and
• responsive to receiving the first truth signal, adjusting at least one fall detection control parameter used to control at least one of:
• generating the body posture signal from the accelerometer signal;
• generating the body acceleration signal from the accelerometer signal;
• and
• determining that the fall detection criteria are met.

A non-transitory computer readable medium storing instructions which, when executed by a control circuit of a medical device, cause the medical device to:

• produce an accelerometer signal;
• generate a body posture signal and a body acceleration signal from the accelerometer signal;
• determine that the body posture signal and the body acceleration signal meet fall detection criteria by:
• determining a first body posture vector from the body posture signal at a first time point;
• determining a second body posture vector from the body posture signal at a second time point later than the first time point of the first body posture vector;
• determining a directional change metric correlated to an angle between the first body posture vector and the second body posture vector;
• determining that the directional change metric is greater than a threshold directional change;
• detecting an acceleration signal spike from the body acceleration signal;
• and
• determining that the acceleration signal spike and the second time point are within a fall time window of each other;
• detect a patient fall in response to the body posture signal and the body acceleration signal meeting the fall detection criteria;
• determine a third body posture vector at a third time point after the second time point;
• determine a directional change metric between the third body posture vector and at least one of the first body posture vector and the second body posture vector;
• determine that the directional change metric meets fall recovery criteria;
• determine a fall recovery time as a time interval from the second time point to the third time point in response to the directional change metric meeting the fall recovery criteria;
• determine at least one of a trend in a frequency of fall detections and a trend in fall recovery time durations in response to detecting the patient fall;
• transmit the determined trend;
• receive a truth signal from another device that is not the medical device indicating that the detected patient fall is a falsely detected patient fall;
• and
• responsive to receiving the truth signal, adjust at least one fall detection control parameter used by the medical device to control at least one of:
• generating the body posture signal from the accelerometer signal;
• generating the body acceleration signal from the accelerometer signal;
• and determining that the fall detection criteria are met.