Pressure ulcer condition sensing and monitoring

• US 6,287,253 B1
• Filed: 06/25/1999
• Issued: 09/11/2001
• Est. Priority Date: 06/25/1999
• Status: Expired due to Term

• Current Assignee: Orthocare Innovations, LLC
• Original Assignee: Sabolich Research & Development
• Inventors: Ortega, Giovani M., Schwabe, George B. IV, Sabolich, John A.
• Primary Examiner(s): Winakur, Eric F.
• Assistant Examiner(s): MARMOR II, CHARLES ALAN
• Application Number:
  US09/344,592
• Time in Patent Office: 809 Days
• Field of Search: 600/300, 600/561, 600/587, 600/595, 128/904, 128/903, 128/897, 368/10, 340/286.07, 340/572.1, 340/275.5, 340/573.1
• US Class Current: 600/300
• CPC Class Codes: A61B 2560/0412 Low-profile patch shaped housings
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/0051 by applying vibrations
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• CPC Class Codes: A61B 5/442 Evaluating skin mechanical properties, e.g. elasticity, hardness, texture, wrinkle assessment
• CPC Class Codes: A61B 5/445 Evaluating skin irritation or skin trauma, e.g. rash, eczema, wound, bed sore
• CPC Class Codes: A61B 5/447 specially adapted for aiding the prevention of ulcer or pressure sore development, i.e. before the ulcer or sore has developed
• CPC Class Codes: A61B 5/6892 Mats

Abstract

A medical sensor responds to a predetermined condition, such as pressure against a human body area susceptible to ulcer formation, and provides wireless communication of the sensing of the condition. It does this by changing a characteristic of a resonant circuit applied to the sensitive area of the human body and energized by electromagnetic induction. An electromagnetic wave transmitter of a monitoring system is disposed adjacent a support, such as a bed, for the human body. A resonant signal detector is disposed adjacent the support. The monitoring system can also comprise a controller that can compute an exposure time value and/or a shift frequency value. With the foregoing an electromagnetic field is provided across a region of the patient on the support, and resonant signals are propagated in response to the predetermined condition and the electromagnetic field and wirelessly communicated to the resonant signal detector. The information obtained from this monitoring and from a remote computer database containing a respective ulceration history for each of a plurality of patients can be used for managing the care of each patient.

Claims

1. A medical sensor responsive to a predetermined condition, the sensor providing wireless communication of the sensing of the condition, comprising:

a substrate applicable to the outside of a human body; and

an electric circuit connected to the substrate, including;

a switch operable in a circuit operative state in response to the predetermined condition, wherein the predetermined condition is pressure against the outside of the human body at a location thereof to which the substrate is applied; and

resonant circuit elements connected to the switch as a resonant circuit to provide a signal at a resonant frequency in response to electromagnetic induction, originating from outside the electric circuit, when the switch is in the circuit operative state.

2. A medical sensor as defined in claim 1, wherein the substrate includes an adhesive portion adapted to adhere to the human body at a location susceptible to decubitus ulceration.

3. A medical sensor as defined in claim 1, wherein the switch is in a different operative state when not responding to the predetermined condition such that the resonant circuit provides a signal at another resonant frequency in response to electromagnetic induction when the switch is in the different operative state.

4. A medical sensor as defined in claim 1, wherein the switch has a variable capacitance responsive to the magnitude of the predetermined condition.

5. A medical sensor providing wireless communication of the sensing of a human body pressure condition, comprising:

a dressing applicable to a human body at a decubitus ulcer site or a site susceptible to developing a decubitus ulcer; and

a pressure responsive circuit connected to the dressing, including;

a switch repeatably operable between a first state and a second state in response to whether pressure above a predetermined threshold is applied by at least partial weight of the human body when the dressing is applied to the human body; and

resonant circuit elements connected to the switch to define on the dressing a self-contained resonant circuit.

6. A medical sensor as defined in claim 5, wherein the pressure responsive circuit further includes an adhesive member adhered to the dressing, the adhesive member having the switch and the resonant circuit elements mounted thereon.

7. A medical sensor as defined in claim 6, wherein the switch includes two electrically conductive members spaced in the first state to define a capacitance and contiguous in the second state to define a short-circuit.

8. A medical sensor as defined in claim 5, wherein the switch includes two electrically conductive members spaced in the first state to define a capacitance and contiguous in the second state to define a short-circuit.

9. A medical sensor responsive to an external human body pressure condition, comprising:

a switch operable in a circuit operative state in response to pressure applied to the outside of a human body;

resonant circuit elements connected to the switch to define a resonant circuit responsive to an electromagnetic field originating outside the sensor at least when the switch is in the circuit operative state; and

means for attaching the switch and the resonant circuit elements to the outside of the human body such that the switch is exposed to an occurrence of the pressure applied to the outside of the human body.

10. A medical sensor as defined in claim 9, wherein the means for attaching includes an adhesive member having the switch and the resonant circuit elements mounted thereon.

11. A medical sensor responsive to a predetermined condition, comprising:

a switch operable in a circuit operative state in response to the predetermined condition;

resonant circuit elements connected to the switch to define a resonant circuit responsive to electromagnetic induction at least when the switch is in the circuit operative state; and

means for attaching the switch and the resonant circuit elements relative to a human body such that the switch is exposed to an occurrence of the predetermined condition;

wherein the predetermined condition is a predetermined pressure magnitude created by at least partial weight of the human body applied at a predetermined location of the human body against a support surface and further wherein the means for attaching is adapted to attach at the predetermined location of the human body such that at least the switch is between the human body and the support surface when the predetermined pressure magnitude is exceeded at the predetermined location.

12. A medical sensor as defined in claim 11, wherein the switch includes a variable capacitor operable between a maximum capacitance state and a minimum capacitance state in response to a change between pressure less than the predetermined pressure magnitude and pressure greater than the predetermined pressure magnitude as the human body shifts relative to the support surface.

13. A method of monitoring pressure applied to a pressure sensitive area of a human body, comprising:

connecting a medical sensor to the pressure sensitive area of the human body;

repeatedly operating a switch in the medical sensor between at least two states in response to repeated movement of the human body causing a pressure at the pressure sensitive area due to at least partial weight of the human body against a support surface to change repeatedly at least between less than a predetermined pressure magnitude and greater than the predetermined pressure magnitude, wherein the switch is connected in a resonant circuit in the medical sensor; and

detecting a respective resonant electromagnetic wave signal generated in response to operating the switch in each of the states.

14. A method as defined in claim 13, wherein connecting the medical sensor to the pressure sensitive area includes attaching an electric circuit of the medical sensor to a dressing of the medical sensor applied to the pressure sensitive area.

15. A method as defined in claim 14, further comprising providing in the vicinity of the human body an electromagnetic field within which the medical sensor connected to the human body is disposed throughout the movement of the human body.

16. A method as defined in claim 15, wherein repeatedly operating a switch includes repeatedly changing the capacitance of a capacitor in the medical sensor.

17. A method as defined in claim 13, wherein repeatedly operating a switch includes repeatedly changing the switch between a capacitive state and a short-circuit state.

18. A system to monitor a pressure sensitive area of a patient positioned on a support, comprising:

an electromagnetic wave transmitter disposed adjacent the support;

a resonant signal detector disposed adjacent the support in operative association with the electromagnetic wave transmitter;

a medical sensor adapted to be attached to the patient such that the medical sensor is responsive to pressure applied to the pressure sensitive area of the patient, the medical sensor including a resonant circuit operative in at least two states in response to pressure applied to the pressure sensitive area of the patient, in at least one of the states the resonant circuit causing a resonant signal to be propagated in cooperative operation with the electromagnetic wave transmitter, wherein the medical sensor is not tangibly attached to the electromagnetic wave transmitter or the resonant signal detector when the medical sensor is attached to the patient; and

a controller connected to the resonant signal detector such that the controller receives a respective signal from the resonant signal detector in response to the resonant signal detector detecting a respective propagated resonant signal, wherein the controller computes an exposure time value in response to a predetermined exposure time monitoring period and a cumulative time within the exposure time monitoring period during which the controller receives signals from the resonant signal detector indicating pressure applied to the pressure sensitive area greater than a predetermined magnitude.

19. A system as defined in claim 18, wherein the controller computes a shift frequency value in response to a predetermined shift frequency monitoring period and the number of transitions relative to receiving signals from the resonant signal detector during the shift frequency monitoring period.

20. A system to monitor a pressure sensitive area of a patient positioned on a support, comprising:

an electromagnetic wave transmitter disposed adjacent the support;

a resonant signal detector disposed adjacent the support in operative association with the electromagnetic wave transmitter;

a medical sensor adapted to be attached to the patient such that the medical sensor is responsive to pressure applied to the pressure sensitive area of the patient, the medical sensor including a resonant circuit operative in at least two states in response to pressure applied to the pressure sensitive area of the patient, in at least one of the states the resonant circuit causing a resonant signal to be propagated in cooperative operation with the electromagnetic wave transmitter, wherein the medical sensor is not tangibly attached to the electromagnetic wave transmitter or the resonant signal detector when the medical sensor is attached to the patient; and

a controller connected to the resonant signal detector such that the controller receives a respective signal from the resonant signal detector in response to the resonant signal detector detecting a respective propagated resonant signal, wherein the controller is programmed to compute a shift frequency value in response to a predetermined monitoring period and the number of transitions relative to receiving signals from the resonant signal detector during the monitoring period.

21. A system to monitor a plurality of external pressure sensitive areas of a patient lying on a bed, comprising:

a variable frequency electromagnetic wave transmitter disposed to one side of the bed;

a resonant signal detector disposed to another side of the bed in operative association with the electromagnetic wave transmitter such that an electromagnetic field generated by the transmitter exists between the transmitter and the detector;

a plurality of medical sensors, wherein each of the medical sensors is adapted to attach to the patient at a respective external pressure sensitive area susceptible to decubitus ulceration, each of the medical sensors includes a respective resonant circuit operative in at least two states in response to pressure applied to the respective medical sensor, in at least one of the states the respective resonant circuit causing a respective resonant signal to be propagated in cooperative operation with the electromagnetic wave transmitter and the electromagnetic field generated by the transmitter; and

a controller connected to the resonant signal detector such that the controller receives a respective signal from the resonant signal detector in response to the resonant signal detector detecting each propagated resonant signal.

22. A system to monitor a plurality of pressure sensitive areas of a patient lying on a bed, comprising:

a variable frequency electromagnetic wave transmitter disposed to one side of the bed;

a resonant signal detector disposed to another side of the bed in operative association with the electromagnetic wave transmitter such that an electromagnetic field generated by the transmitter exists between the transmitter and the detector;

a plurality of medical sensors, wherein each of the medical sensors is adapted to attach to the patient at a respective pressure sensitive area susceptible to decubitus ulceration, each of the medical sensors includes a respective resonant circuit operative in at least two states in response to pressure applied to the respective medical sensor, in at least one of the states the respective resonant circuit causing a respective resonant signal to be propagated in cooperative operation with the electromagnetic wave transmitter and the electromagnetic field generated by the transmitter; and

a controller connected to the resonant signal detector such that the controller receives a respective signal from the resonant signal detector in response to the resonant signal detector detecting each propagated resonant signal;

wherein the controller is programmed to compute an exposure time value relative to each of the medical sensors, wherein the exposure time value for each medical sensor is computed in response to a predetermined exposure time monitoring period and a cumulative time within the exposure time monitoring period during which the controller receives signals from the resonant signal detector indicating pressure applied to the respective medical sensor greater than a predetermined magnitude.

23. A system as defined in claim 22, wherein the controller is further programmed to compute, relative to each of the medical sensors, a shift frequency value in response to a predetermined shift frequency monitoring period and the number of transitions in signals received from the resonant signal detector during the shift frequency monitoring period for the respective medical sensor.

24. A system to monitor a plurality of pressure sensitive areas of a patient lying on a bed, comprising:

a variable frequency electromagnetic wave transmitter disposed to one side of the bed;

a resonant signal detector disposed to another side of the bed in operative association with the electromagnetic wave transmitter such that an electromagnetic field generated by the transmitter exists between the transmitter and the detector;

a plurality of medical sensors, wherein each of the medical sensors is adapted to attach to the patient at a respective pressure sensitive area susceptible to decubitus ulceration, each of the medical sensors includes a respective resonant circuit operative in at least two states in response to pressure applied to the respective medical sensor, in at least one of the states the respective resonant circuit causing a respective resonant signal to be propagated in cooperative operation with the electromagnetic wave transmitter and the electromagnetic field generated by the transmitter; and

a controller connected to the resonant signal detector such that the controller receives a respective signal from the resonant signal detector in response to the resonant signal detector detecting each propagated resonant signal;

wherein the controller is programmed to compute, relative to each of the medical sensors, a shift frequency value in response to a predetermined monitoring period and the number of transitions in signals received from the resonant signal detector during the monitoring period for the respective sensor.

25. A method of monitoring one or more pressure sensitive areas of a patient on a support, comprising:

providing an electromagnetic field across a region of the patient on the support; and

propagating, in operative association with the electromagnetic field, resonant signals in response to pressure above a predetermined magnitude at one or more external areas of the patient susceptible to ulceration and wirelessly communicating the resonant signals to a resonant signal detector disposed adjacent the support.

26. A method as defined in claim 25, further comprising communicating signals to a controller connected to the resonant signal detector, and determining with the controller the amount of time that pressure above the predetermined magnitude existed and the number of changes between pressure above the predetermined magnitude and pressure below the predetermined magnitude.

27. A method as defined in claim 26, further comprising computing with the controller an exposure time value relative to the one or more external areas of the patient susceptible to ulceration, wherein the exposure time value for each medical sensor is computed in response to a predetermined exposure time monitoring period and the cumulative time within the exposure time monitoring period during which pressure greater than the predetermined magnitude existed at the respective area.

28. A method as defined in claim 27, further comprising computing, with the controller and relative to the one or more external areas of the patient susceptible to ulceration, a shift frequency value in response to a predetermined shift frequency monitoring period and the number of changes between pressure above the predetermined magnitude and pressure below the predetermined magnitude.

29. A method as defined in claim 26, further comprising computing, with the controller and relative to the one or more external areas of the patient susceptible to ulceration, a shift frequency value in response to a predetermined monitoring period and the number of changes between pressure above the predetermined magnitude and pressure below the predetermined magnitude.

30. A method as defined in claim 25, wherein:

providing an electromagnetic field includes transmitting radio frequency signals having different respective frequencies within a predetermined frequency range; and

propagating resonant signals includes emitting from each respective external area resonant signals having a respective resonant frequency responsive to a respective frequency of the radio frequency signals.

31. A method as defined in claim 30, wherein the radio frequency signals are transmitted concurrently.

32. A method as defined in claim 30, wherein the radio frequency signals are transmitted sequentially such that signals having only one of the different respective frequencies is transmitted at a time.

33. A method as defined in claim 30, further comprising propagating, in operative association with the electromagnetic field, different resonant signals in response to pressure below the predetermined magnitude at any of the one or more external areas of the patient susceptible to ulceration and wirelessly communicating the different resonant signals to the resonant signal detector.

34. A method as defined in claim 33, wherein propagating resonant signals and propagating different resonant signals include operating a switch in a resonant circuit at a respective one of the external areas between a short-circuit condition and a capacitance condition of the switch in response to pressure applied to the switch.

35. A method as defined in claim 25, further comprising propagating, in operative association with the electromagnetic field, different resonant signals in response to pressure below the predetermined magnitude at any of the one or more external areas of the patient susceptible to ulceration and wirelessly communicating the different resonant signals to the resonant signal detector.

36. A method as defined in claim 35, wherein propagating resonant signals and propagating different resonant signals include operating a switch in a resonant circuit at a respective one of the external areas between a short-circuit condition and a capacitance condition of the switch in response to pressure applied to the switch.

37. A method as defined in claim 25, wherein providing an electromagnetic field includes generating, at a first time, the electromagnetic field from a first location relative to the region and generating, at a second time, the electromagnetic field from a second location relative to the region.

38. A method as defined in claim 31, wherein providing an electromagnetic field includes periodically actuating a transmitter to generate the electromagnetic field temporarily so that the electromagnetic field is not constantly present across the region of the patient or the support.

39. A method of monitoring for a pressure sensor adapted to be attached externally to a patient, comprising:

transmitting, across a region in which a patient is disposed, a driving signal having at least one frequency to which a pressure sensor adapted to be attached externally to the patient is responsive if the pressure sensor is attached to the patient and operational;

detecting whether a first response signal is emitted from the sensor in the region in response to the driving signal, the first response signal indicating the presence of the operational sensor in the region;

detecting whether a second response signal is emitted from the sensor in the region in response to the driving signal, the second response signal indicating an external pressure condition related to the patient; and

repeating the transmitting and detecting steps for respective selected frequencies of the driving signal and respective responsive frequencies for the first and second response signals for a plurality of sensors adapted to be attached to the patient such that each sensor is uniquely identified.

40. A method of monitoring for a pressure sensor adapted to be attached externally to a patient, comprising:

transmitting, across a region in which a patient is disposed, a driving signal having at least one frequency to which a pressure sensor adapted to be attached externally to the patient is responsive if the pressure sensor is attached to the patient and operational;

detecting whether a first response signal is emitted from the sensor in the region in response to the driving signal, the first response signal indicating the presence of the operational sensor in the region; and

detecting whether a second response signal is emitted from the sensor in the region in response to the driving signal, the second response signal indicating an external pressure condition related to the patient;

wherein the driving signal is transmitted from different locations relative to the region and wherein detecting occurs from different locations relative to the region such that the first and second response signals are within detection range of at least one of the locations.

41. A method of monitoring for a pressure sensor adapted to be attached externally to a patient, comprising:

transmitting, across a region in which a patient is disposed, a driving signal having at least one frequency to which a pressure sensor adapted to be attached externally to the patient is responsive if the pressure sensor is attached to the patient and operational;

detecting whether a first response signal is emitted from the sensor in the region in response to the driving signal, the first response signal indicating the presence of the operational sensor in the region; and

detecting whether a second response signal is emitted from the sensor in the region in response to the driving signal, the second response signal indicating an external pressure condition related to the patient;

wherein transmitting the driving signal includes sequentially providing the driving signal from different locations relative to the region and wherein detecting occurs from different locations relative to the region such that the first and second response signals are within detection range of at least one of the locations.

42. A method of monitoring for a sensor adapted to be attached to a patient, comprising:

transmitting, across a region in which a patient is disposed, a first driving signal having a first frequency to which a sensor adapted to be attached to the patient is responsive if the sensor is attached to the patient and if the sensor is in at least a first operating state;

detecting whether a first response signal is emitted from the sensor in the region in response to the first driving signal;

in response to detecting the first response signal, transmitting across the region a second driving signal having a second frequency to which the sensor is responsive in at least a second operating state; and

detecting whether a second response signal is emitted from the sensor in response to the second driving signal, the second response signal indicating a condition related to the patient.

43. A method of monitoring a pressure sensitive area of a patient on a support, comprising:

communicating signals indicating (1) that pressure above a predetermined magnitude has been exerted against the pressure sensitive area and (2) changes between pressure above the predetermined magnitude and pressure below the predetermined magnitude;

computing a shift frequency value in response to a predetermined shift frequency monitoring period and the number of changes between pressure above the predetermined magnitude and pressure below the predetermined magnitude occurring during the predetermined shift frequency monitoring period as indicated by the communicated signals; and

moving the patient in response to the computed shift frequency value.

44. A method as defined in claim 43, further comprising computing an exposure time value, wherein the exposure time value is computed in response to a predetermined exposure time monitoring period and the cumulative time within the exposure time monitoring period during which pressure greater than the predetermined magnitude was exerted against the pressure sensitive area as indicated by the communicated signals, and moving the patient in response to both the computed shift frequency value and the computed exposure time value.

45. A computer-implemented pressure ulcer management method, comprising:

maintaining in a computer a database containing a respective ulceration history for each of a plurality of patients, each ulceration history including data identifying information relevant to the respective patient'"'"'s susceptibility to ulcer formation;

monitoring the patients, including for each patient sensing pressure application to at least one location on the respective patient at risk to ulcer formation and communicating additional data to the computer in response to sensed pressure application;

storing in the computer the additional data with the data in the database; and

managing the care of each patient in response to that patient'"'"'s respective ulceration history and the respective stored additional data.

46. A method as defined in claim 45, wherein the additional data includes for each patient the number of pressure applications and a cumulative exposure time to pressure for the at least one location on the respective patient at risk to ulcer formation.

47. A method as defined in claim 45, wherein each ulceration history further includes respective patient historical data identifying any unhealed ulcers, previous ulcers, when each previous ulcer was detected, when each previous ulcer was healed, the number of pressure applications sensed during the period between when a respective previous ulcer was detected and when the respective previous ulcer was healed, and the cumulative exposure time to pressure during the period between when a respective previous ulcer was detected and when the respective previous ulcer was healed.

48. A method as defined in claim 47, wherein:

the additional data includes the number of pressure applications and a cumulative exposure time to pressure for each unhealed ulcer; and

managing the care of each patient includes computing an estimated remaining treatment period for a respective unhealed ulcer in response to the historical data for at least one previous ulcer of the patient and the additional data for the respective unhealed ulcer.

49. A method as defined in claim 45, wherein each ulceration history further includes historical data identifying previous ulcers, the number of previous ulcers occurring at the same location of the respective patient, when each previous ulcer was detected at the respective location, and when each previous ulcer was healed.

50. A method as defined in claim 49, wherein:

managing the care of each patient includes determining in the computer a respective frequency of ulcer formation in response to the historical data for each location; and

managing the care of each patient further includes determining in the computer a respective time since the last previous ulcer was healed at each respective location for the respective patient and comparing the determined time with the respective determined frequency of ulcer formation for the respective location.

51. A method as defined in claim 49, wherein:

the historical data further identifies pressure applications sensed during the period between when a respective previous ulcer was healed and when the next ulcer at the same respective location was detected and the cumulative exposure time to pressure during the period between when the respective previous ulcer was healed and when the next ulcer at the same respective location was detected;

the additional data includes the number of pressure applications to a respective one of the locations of previous ulcers and a cumulative exposure time to pressure for each such location since the last previous ulcer was healed at each respective location for the patient; and

managing the care of each patient further includes comparing (1) the number of pressure applications to a respective one of the locations of previous ulcers and the cumulative exposure time to pressure for each such location since the last previous ulcer was healed at each respective location for the patient with (2) pressure applications sensed during the period between when a respective previous ulcer was healed and when the next ulcer at the same respective location was detected and the cumulative exposure time to pressure during the period between when the respective previous ulcer was healed and when the next ulcer at the same respective location was detected.

52. A computer-implemented pressure ulcer management method, comprising:

maintaining in a computer a database containing a respective ulceration history for each of a plurality of patients, each ulceration history including historical data identifying previous ulcers, the number of previous ulcers occurring at the same location of the respective patient, when each previous ulcer was detected at the respective location, and when each previous ulcer was healed;

monitoring the patients, including for each patient sensing pressure application to each previous ulcer location identified by the data in the database and communicating additional data to the computer in response to sensed pressure application; and

storing in the computer the additional data with the data in the database.

53. A method as defined in claim 52, further comprising:

determining in the computer a respective frequency of ulcer formation in response to the historical data for each location; and

determining in the computer, for each patient, a respective time since the last previous ulcer was healed at each respective location for the respective patient and comparing the determined time with the respective determined frequency of ulcer formation for the respective location.

54. A method as defined in claim 52, wherein:

the historical data further identifies pressure applications sensed during the period between when a respective previous ulcer was healed and when the next ulcer at the same respective location was detected and the cumulative exposure time to pressure during the period between when the respective previous ulcer was healed and when the next ulcer at the same respective location was detected;

the additional data includes the number of pressure applications to a respective one of the locations of previous ulcers and a cumulative exposure time to pressure for each such location since the last previous ulcer was healed at each respective location for the patient; and

the method further comprises, for each patient, comparing (1) the number of pressure applications to a respective one of the locations of previous ulcers and the cumulative exposure time to pressure for each such location since the last previous ulcer was healed at each respective location for the patient with (2) pressure applications sensed during the period between when a respective previous ulcer was healed and when the next ulcer at the same respective location was detected and the cumulative exposure time to pressure during the period between when the respective previous ulcer was healed and when the next ulcer at the same respective location was detected.

55. A computer-implemented pressure ulcer management method, comprising:

maintaining in a computer a database containing a respective predetermined ulceration event for each of a plurality of patients;

monitoring the patients, including for each patient sensing pressure application to at least one location of the respective patient susceptible to ulceration and communicating data to the computer defining shifts of the respective patient between pressure-on and pressure-off events relative to the at least one location in response to sensed pressure application; and

correlating in the computer the communicated data with the respective predetermined ulceration event for each of the patients.

56. A method as defined in claim 55, wherein:

the predetermined ulceration event includes a time the respective patient is to be turned relative to the respective at least one location susceptible to ulceration; and

correlating the communicated data with the respective predetermined ulceration event includes determining whether a transition from a pressure-on event to a pressure-off event occurred at the respective time.

57. A method as defined in claim 55, wherein:

the predetermined ulceration event includes a pressure-on threshold relative to the respective at least one location susceptible to ulceration; and

correlating the communicated data with the respective predetermined ulceration event includes determining the length of time from a sensed pressure exceeding the predetermined pressure-on threshold to the next sensed pressure-off event.