Patient monitoring system employing array of force sensors on a bedsheet or similar substrate

• US 6,840,117 B2
• Filed: 03/03/2003
• Issued: 01/11/2005
• Est. Priority Date: 01/08/1997
• Status: Expired due to Term

• Current Assignee: Trustees of Boston University
• Original Assignee: Trustees of Boston University
• Inventors: Hubbard, James E. Jr.
• Primary Examiner(s): NOORI, MAX H
• Application Number:
  US10/378,340
• Publication Number:
  US 20030136201A1
• Time in Patent Office: 680 Days
• Field of Search: 738/620.41, 738/620.42, 738/620.43, 738/620.44, 738/620.45, 738/620.46
• US Class Current: 73/862.041
• CPC Class Codes: A43B 3/00 Footwear characterised by the shape or the use
• CPC Class Codes: A43B 3/34 with electrical or electronic arrangements
• CPC Class Codes: A61B 2562/0252 Load cells
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• CPC Class Codes: A61B 5/1115 Monitoring leaving of a patient support, e.g. a bed or a wheelchair
• CPC Class Codes: A61B 5/112 Gait analysis
• CPC Class Codes: A61B 5/1126 using a particular sensing technique
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01526 using piezoelectric elements
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015
• CPC Class Codes: G01G 19/44 for weighing persons
• CPC Class Codes: G01G 19/445 in a horizontal position
• CPC Class Codes: G01G 23/3728 with wireless means
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G06V 40/10 Human or animal bodies, e.g. vehicle occupants or pedestrians; Body parts, e.g. hands
• CPC Class Codes: G06V 40/25 Recognition of walking or running movements, e.g. gait recognition

Abstract

A patient monitoring system includes a replaceable laminar sensor to be placed on a bed, the sensor including distributed force sensing elements providing output signals to processing apparatus including a near-bed processor and a central processor coupled to the near-bed processor by a wireless communication link. The processing apparatus applies spatial weighting to the sensor output signals to derive the force distribution across the sensor, and processes the force distribution over time to generate patient status information such as patient presence, position, agitation, seizure activity, respiration, and security. This information can be displayed at a central monitoring station, provided to a paging system to alert attending medical personnel, and used to update medical databases. The sensor may be manufactured from layers of olefin film and conductive ink to form capacitive sensing elements.

Claims

1. A system for sensing status of a patient in a bed comprising:

a replaceable laminar sensor on said bed;

said laminar sensor having a plurality of force sensing elements distributed two-dimensionally throughout said sensor; and

processing apparatus responsive to forces sensed by said sensor for forming a spatially weighted sum of the forces sensed by said sensor to provide a distribution of the forces throughout said laminar sensor, said processing apparatus providing an indication over time of a patient status in response to said weighted average.

2. The system of claim 1 wherein said laminar sensor comprises a sheet having discrete sensors therein.

3. The system of claim 2 wherein said discrete sensors include one of capacitive sensors, piezoelectric sensors, and resistive sensors.

4. The system of claim 1 wherein said laminar sensor further includes conductors extending from the discrete sensors to a connection point at an edge of said sheet.

5. The system of claim 2 wherein said sheet is dimensioned to cover said bed over a predetermined range of patient movement.

6. The system of claim 1 wherein said processing apparatus includes a near-bed processor and a central processor in communication with said near-bed processor through a communication link.

7. The system of claim 6 wherein said communication link is a wireless link having interfaces at said near-bed processor and said central processor.

8. The system of claim 1 wherein said processing apparatus provides patient status information including information regarding patient presence, patient position, patient agitation, patient seizures, patient respiration, and patient security.

9. The system of claim 1 wherein said processing apparatus provides patient status information relative to sleep disorders.

10. The system of claim 1 wherein said processing apparatus provides patient status information relative to patient drug reactions.

11. The system of claim 1 wherein said processing apparatus provides information relative to the presence or absence of patient activity sufficient to avoid bed sores.

12. The system of claim 1 further including a database for recording patient status.

13. The system of claim 12 wherein said processing apparatus provides adaptive indications of patient status in response to database information and sensor signals.

14. A sensing sheet for use in a patient monitoring system, the patient monitoring system including processing apparatus operative to calculate a spatially weighted sum of the respective values of sensor signals generated by the sensing sheet, the spatially weighted sum being calculated using a set of predetermined two-dimensional spatial weight values, the sensing sheet comprising:

a planar, flexible, electrically insulative substrate, the substrate having length and width substantially corresponding to the length and width of a patient'"'"'s bed; and

a pattern of sensing elements on the substrate, the sensing elements being spaced apart to define a two-dimensional sensing area on the patient'"'"'s bed when the sensing sheet is placed thereon, the sensing elements having respective sizes, shapes and locations in relation to the predetermined two-dimensional spatial weight values such that the spatially weighted sum accurately reflects the spatial distribution of forces existing between a patient and the patient'"'"'s bed when the sensing sheet is disposed therebetween.

15. A sensing sheet according to claim 14, wherein the substrate includes a set of laminated layers.

16. A sensing sheet according to claim 14, wherein the sensing elements comprise capacitors made from conductive planar elements disposed on the substrate.

17. A sensing sheet for use in a patient monitoring system, the patient monitoring system including processing apparatus operative to calculate a spatially weighted sum of the respective values of sensor signals generated by the sensing sheet, the spatially weighted sum being calculated using a set of predetermined two-dimensional spatial weight values, the sensing sheet comprising:

a first electrically insulative film, the first film having length and width substantially corresponding to the length and width of a patient'"'"'s bed and having a pattern of conductive electrodes formed thereon, the conductive electrodes being spaced apart on the film to define a two-dimensional sensing area extending substantially entirely across the patient'"'"'s bed when the sensing sheet is placed thereon, the conductive electrodes having respective sizes, shapes and locations in relation to the predetermined two-dimensional spatial weight values such that the spatially weighted sum accurately reflects the spatial distribution of forces existing between a patient and the patient'"'"'s bed when the sensing sheet is disposed therebetween, the first film also including a set of conductive traces creating individual conductive paths from the electrodes to a connection area of the sensing sheet;

a second electrically insulative film laminated with the first film, the second film having length and width substantially the same as the length and width of the first film, the second film having a pattern of conductive electrodes formed thereon at respective locations directly opposite the respective locations of the electrodes on the first film, the second film also including conductive traces operative to electrically interconnect all of the conductive electrodes on the second film to each other and to the connection area of the sensing sheet; and

a multi-conductor cable extending from the connection area of the sensing sheet and including a multi-terminal connector, the conductors of the cable being operative to create respective conductive paths from respective conductive traces of the first and second films to respective terminals of the multi-terminal connector.

18. A sensing sheet according to claim 17, wherein the signal traces are shielded by corresponding ground traces.