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 system for continuously monitoring a patient, comprising:
a first sensor comprising a first detector configured to detect a first time-dependent physiological waveform indicative of one or more contractile properties of the patient's heart;
a second sensor comprising a second detector configured to detect a second time-dependent physiological waveform indicative of one or more contractile properties of the patient's heart;
three motion-detecting sensors configured to be positioned on a forearm, upper arm, and a body location other than the forearm or upper arm of the patient, each of the motion-detecting sensors generating at least one motion waveform indicative of motion of the location on the patient's body to which the motion-detecting sensor is affixed;
a processing component configured to
receive the first time-dependent physiological waveform, the second time-dependent physiological waveform, and the motion waveforms obtained from the three motion-detecting sensors
process at least one or more of the motion waveforms obtained from the three motion-detecting sensors to determine a time-dependent arm height for the patient;
process the first and second time-dependent physiological waveforms and a correction value determined from the time-dependent arm height to determine a time-dependent blood pressure for the patient;
process one or more of the motion waveforms obtained from the three motion-detecting sensors to determine a time-dependent posture state for the patient; and
determine an alarm condition by comparing the blood pressure to a predetermined alarm criterion that is regulated according to the patient's time-dependent posture state, wherein if the patient has undergone a change in posture state that would result in an expected drop in blood pressure, the alarm criterion is altered to reflect the expected drop in blood pressure; and
a display component configured to continuously display an icon indicative of the patient's time-dependent posture state and alarm condition.
2. The system of claim 1 , wherein the first time-dependent physiological waveform is an ECG waveform.
3. The system of claim 1 , wherein the second time-dependent physiological waveform is a plethysmogram waveform.
4. The system 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.