Wheelchair alarm system and method

• US 8,203,454 B2
• Filed: 03/02/2009
• Issued: 06/19/2012
• Est. Priority Date: 03/03/2008
• Status: Active Grant

• Current Assignee: Massachusetts Institute of Technology, The General Hospital Corporation (Mass General Brigham, Inc.)
• Original Assignee: Massachusetts Institute of Technology, The General Hospital Corporation (Mass General Brigham, Inc.)
• Inventors: Knight, Heather-Marie Callanan, Lee, Jae-Kyu, Ma, Hongshen, Kattany, Lauren
• Primary Examiner(s): Nguyen, Hung T.
• Application Number:
  US12/396,402
• Publication Number:
  US 20100045454A1
• Time in Patent Office: 1,205 Days
• Field of Search: 340/573.1, 340/573.7, 340/539.12, 340/665, 340/666, 340/667, 340/686.1, 340/686.6
• US Class Current: 340/573.1
• CPC Class Codes: G08B 21/0453 worn on the body to detect health condition by physiological monitoring, e.g. electrocardiogram, temperature, breathing detecting, measuring or recording for diagnostic purposes A61B5/00
• CPC Class Codes: G08B 21/0469 Presence detectors to detect unsafe condition, e.g. infrared sensor, microphone G08B21/0476 takes precedence

Abstract

A wheelchair alarm system and method for preventing falls for patients at risk by recognizing the gesture of a patient attempting to stand. The wheelchair alarm system uses an array of proximity sensors and pressure sensors to create a map of the patient'"'"'s sitting position, and then uses gesture recognition algorithms to determine when a patient is attempting to stand up. The wheelchair alarm system responds with light and voice alarms that can encourage the patient to remain seated and/or to make use of the system'"'"'s integrated nurse-call function. The wheelchair alarm system can be seamlessly integrated into existing hospital WiFi networks, sending messages to the nurse call system as well as providing the patient'"'"'s location.

Claims

1. A method for preventing a person from falling from a chair, comprising the steps of:

sensing a plurality of seating position parameters with a plurality of sensors located on the chair;

determining at least one gesture state from the plurality of seating position parameters;

determining whether the at least one gesture state indicates or predicts a risk condition;

providing an alarm when the risk condition is indicated or predicted by a processor; and

wherein the step of determining the at least one gesture state from the plurality of seating position parameters comprises;

deriving a plurality of derived features from the seating position parameters;

determining from at least one of the plurality of derived features a probabilistic score for the at least one gesture state; and

triggering the at least one gesture state when the probabilistic score is above a threshold score.

2. The method of claim 1, wherein the probabilistic score is calculated by adding the derived features associated with the at least one gesture state.

3. The method of claim 2, wherein the step of calculating the probabilistic score comprises weighting the at least one derived feature with a patients weight.

4. The method of claim 1, wherein the plurality of seating position parameters comprise a plurality of distances between a chair back and a patient, a plurality of pressures on a chair seat, and a plurality of pressures on a set of chair arm rests.

5. The method of claim 4, wherein the plurality of derived features comprises at least one static derived feature, at least one velocity derived feature, at least one time derivative derived feature, and at least one integrated derived feature.

6. The method of claim 4, wherein the at least one gesture state is one of a slouching gesture state, a high movement gesture state, an attempting to exit chair gesture state, a standing up gesture state, and a falling out of chair gesture state, and a out of chair gesture state.

7. The method of claim 1, wherein the alarm comprises at least one of a local voice alarm, a local visual alarm, and a remote alarm.

8. The method of claim 1, further comprising calibrating a set of sensitivity level parameters for a specific patient.

9. The method of claim 8, wherein the set of sensitivity level parameters are used to scale the plurality of seating position parameters.

10. The method of claim 1, further comprising the step of initiating an electronic voice communication channel.

11. The method of claim 1, further comprising the step of initiating a nurse call.

12. The method of claim 1, further comprising the step of retrofitting the plurality of sensors on the wheelchair.

13. An alarm system for a chair, the alarm system comprising:

a plurality of sensors configured to generate a plurality of seating position parameters;

an alarm;

a controller configured to receive the plurality of seating position parameters, determine at least one gesture state from the plurality of seating position parameters, determine whether the at least one gesture indicates or predicts a risk condition, and activate the alarm when the risk condition is indicated or predicted; and

wherein the controller is further configured to derive a plurality of derived features from the seating position parameters, determine from at least one of the plurality of derived features a probabilistic score for the at least one gesture state, and trigger the at least one gesture state when the probabilistic score is above a threshold score.

14. The alarm system of claim 13, wherein the plurality of sensors comprises a plurality of proximity sensors and a plurality of force sensors.

15. The alarm system of claim 13, wherein the plurality of sensors are fitted in a wheelchair.

16. The alarm system of claim 13, further comprising a nurse call button configured to cause the controller to transmit a nurse call.

17. The alarm system of claim 13, further comprising a wireless connection.

18. The alarm system of claim 13, wherein the alarm is at least one of a local audible alarm, a local visual alarm, and a remote alarm.