Alarm system that processes both motion and vital signs using specific heuristic rules and thresholds
The invention provides a body-worn monitor that measures a patient's vital signs (e.g. blood pressure, SpO2, heart rate, respiratory rate, and temperature) while simultaneously characterizing their activity state (e.g. resting, walking, convulsing, falling). The body-worn monitor processes this information to minimize corruption of the vital signs by motion-related artifacts. A software framework generates alarms/alerts based on threshold values that are either preset or determined in real time. The framework additionally includes a series of ‘heuristic’ rules that take the patient's activity state and motion into account, and process the vital signs accordingly. These rules, for example, indicate that a walking patient is likely breathing and has a regular heart rate, even if their motion-corrupted vital signs suggest otherwise.
1. A method for continuously monitoring a patient, comprising the following steps:
detecting a first time-dependent physiological waveform indicative of one or more contractile properties of the patient's heart with a first sensor comprising a first detector configured to be worn on the patient's body;
detecting a second time-dependent physiological waveform indicative of one or more contractile properties of the patient's heart with a second sensor comprising a second detector configured to be worn on the patient's body;
detecting sets of time-dependent motion waveforms with at least two motion-detecting sensors positioned on locations selected from a forearm, upper arm, and a body location other than the forearm or upper arm of the patient, wherein each set of motion waveforms is indicative of motion of the location on the patient's body to which it is affixed;
processing the first and second time-dependent physiological waveforms to determine at least one vital sign from the patient;
analyzing at least a portion of the sets of time-dependent motion waveforms with a motion-determining algorithm to determine if the patient is in an activity state selected from the group of resting, moving, sitting, standing, walking, running, falling, lying down, and convulsing; and
generating an alarm by processing the patient's activity state and comparing the vital sign to a predetermined alarm criteria corresponding to the activity state.
2. The method of claim 1 , wherein the first time-dependent physiological waveform is an ECG waveform.
3. The method of claim 1 , wherein the second time-dependent physiological waveform is a plethysmogram waveform.
4. The method of claim 1 , wherein the first time-dependent physiological waveform is an ECG waveform and the second time-dependent physiological waveform is a plethysmogram waveform.
5. The method of claim 1 , wherein the sets of time-dependent motion waveforms are detected from a first motion-detecting sensor positioned on an arm at the wrist, a second motion-detecting sensor positioned on the same arm at the upper arm, and a third motion-detecting sensor positioned on the chest.
6. The method of claim 4 , wherein the sets of time-dependent motion waveforms are detected from a first motion-detecting sensor positioned on an arm at the wrist, a second motion-detecting sensor positioned on the same arm at the upper arm, and a third motion-detecting sensor positioned on the chest.