WO2010099488A1 - Contact tracking using wireless badges - Google Patents

Abstract

This application discusses apparatus and methods for tracking contacts between various entities in a region. An apparatus includes portable transceiver device having a radio, memory and a power supply. The portable transceiver device can detect and record a history of proximity to other transceiver devices. The portable transceiver device can receive information related to disease exposure of the transceiver device and can include a processing component to compute an exposure potential to a contagious disease using the history of proximity and the disease exposure information.

Description

CONTACT TRACKING USING WIRELESS BADGES

Related Applications

This application claims the benefit of priority from U.S. Provisional Patent Application Serial No. 61/156,396 filed February 27, 2009, and U.S. Provisional Application Serial No. 61/235,339 filed August 19, 2009, which applications are incorporated herein by reference in their entirety.

FIELD OF TECHNOLOGY

The present subject matter relates to hand hygiene compliance systems and in particular hand hygiene compliance systems using wireless badges.

BACKGROUND

According to the Center for Disease Control (CDC), nearly 2 million patients in US hospitals acquire infection, and approximately 90,000 of these patients die because of their infection. The importance of hand washing in reducing risk of infections was first introduced by Dr. Ignaz Semmelweis in his historical study in 1847. Recent studies have provided substantial evidence suggesting that hand hygiene significantly reduce incidences of infections.

The CDC estimates only 40% adherence rate of hand hygiene practices in US hospitals and recommends establishing a performance indicator by monitoring and recording hand washings to help improve the adherence. Although good hand hygiene can prevent the spread of disease, once a disease is detected, understanding the migration of the disease both before and after detection can assist in containing the disease and in preventing and minimizing the effects of the disease in a subsequent outbreak.

SUMMARY

This document provides method and apparatus for calculating exposure potential to a disease on a transceiver device using a history of proximity to other transceiver devices. In various embodiments, the transceiver device is portable and includes a radio, memory and a power source. The transceiver device detects other transceiver devices and records the history of proximity to each of the other device using the memory.

A method embodiment includes receiving health information at a portable first transceiver device and calculating an exposure potential using the health information and a history of proximity to other transceiver devices. In various embodiments, the transceiver device processes a simulation using the recorded history and the health information to calculate the exposure potential.

A system embodiment includes a computer to receive health information, a portable first transceiver device and one or more second transceiver devices. The portable first transceiver device includes a wireless transceiver, memory and a processing component. The portable first transceiver device is configured to detect and record a history of proximity to the one or more second transceiver devices. In various embodiments, at least one of the other transceiver devices includes a hygiene device. This Summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details about the present subject matter are found in the detailed description and the appended claims. The scope of the present invention is defined by the appended claims and their legal equivalents.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows a hand hygiene tracking system according to one embodiment of the present subject matter.

FIG. 2 shows a block diagram of a hand hygiene station, wearable badge, proximity device and computer according to one embodiment of the present subject matter.

FIG. 3 shows a badge and computer according to one embodiment of the present subject matter.

FIG. 4 shows a badge according to one embodiment of the present subject matter.

FIG. 5 shows a flow chart of a method for detecting hand cleaning hygiene data in a hand hygiene compliance system according to one embodiment of the present subject matter. FIG. 6 is a flowchart of a method for collecting hand hygiene data in a hand hygiene compliance tracking system according to one embodiment of the present subject matter.

FIG. 7 shows a flowchart for a method to extend the battery life of a badge battery according to one embodiment of the present subject matter.

FIG. 8 illustrates a flowchart of a method for synchronizing a device clock within a system according to one embodiment of the present subject matter.

FIG. 9 is a flowchart of a method for tracking hand hygiene compliance according to one embodiment of the present subject matter.

FIG. 10 includes a flowchart of a method to estimate a probability of infection according to one embodiment of the present subject matter.

DETAILED DESCRIPTION The following detailed description of the present invention refers to subject matter in the accompanying drawings which show, by way of illustration, specific aspects and embodiments in which the present subject matter may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present subject matter. References to "an", "one", or "various" embodiments in this disclosure are not necessarily to the same embodiment, and such references contemplate more than one embodiment. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope is defined only by the appended claims, along with the full scope of legal equivalents to which such claims are entitled. The present subject matter, in various embodiments, provides a tracking system for monitoring and recording hand hygiene practices as well as for tracking contact between personnel and contact between personnel and equipment monitored as part of the system. Components of the system include small wireless transceiver devices that can be easily deployed at various locations and in concealed manners when desired. The system also includes wearable transceiver devices such as badges, key fobs, bracelets, belt clips, or similar items that contain small computers with wireless networking and memory. The wireless transceiver devices are adapted to detect, among other things, hand hygiene related events and communicate data related to those events to the wearable badges. Such events include, but are not limited to, a person activating a hand sanitizer, soap dispenser and/or hand washing station. When such events are associated with an activity, such as a badge-wearing person entering and exiting a room where hand hygiene is beneficial, the system is useful for detecting compliance with hand hygiene policies established by a health care provider. Data related to the hand hygiene events is collected and stored by the badges. The data is subsequently transferred to a computer for processing and analysis. In various embodiments, data is transferred from the badges to the computer via wireless communications. In various embodiments, data is transferred from the badge memory using a wired connection, including but not limited to, a Universal Serial Bus (USB) connection. Other connection protocols are possible without departing from the scope of the present subject matter.

FIG. 1 shows a hand hygiene compliance system 100 according to one embodiment of the present subject matter. The system includes a computer 101, hand hygiene stations 102, proximity devices 103 and radio badges 104. The system 100 generates data related to the operation of the hand hygiene stations 102 and the movement of badge wearing people within the facility. The illustrated system 100 monitors hand hygiene in a hospital. It is understood that other installations of a system are possible where hand hygiene compliance can benefit the welfare of personnel within or outside such a facility including, but not limited to, schools, restaurants, hospices, clean room facilities, laboratories and food processing, food preparation and food services facilities.

In a hospital setting, it is common to locate hand hygiene stations 102 close to areas where hand hygiene is beneficial, such as near the door of each patient room or near a common travel area between patient stations to make access to the devices convenient for compliance with hand hygiene protocol. The illustrated embodiment includes a hand hygiene station 102 next to a nurses' station 110. The system tracks hand hygiene using radio badges 104 to record and store hand hygiene related data. In a hospital facility, doctors, nurses, staff, patients and visitors may all wear a radio badge 104. Each hand hygiene station 102 includes radio electronics that are triggered when the station is used. Upon being triggered, the radio electronics transmit data. A radio badge in proximity to an activated hygiene station receives the transmission. In various embodiments, the badge 104 records data within the transmission for subsequent processing using the computer 101. In various embodiments, the badge 104 responds to the transmission and exchanges and records data with the hand hygiene station 102. In various embodiments, the badge 104 and station 102 will exchange identifying information and data related to the hand hygiene activity initiating the communications. In some embodiments, the badge 104 stores one or more pieces of data in memory including, but not limited to, a unique identification code (ID) associated with the hand hygiene station, signal strength of received transmissions, time of day, date or combinations thereof. The data is subsequently downloaded from each badge in the system to the computer and then processed and analyzed to track hand hygiene compliance. In some embodiments, the hand hygiene station transmits data related to its operation or condition including, but not limited to, the levels of any consumable products, battery status, operational status or combinations thereof. Such information is used to schedule maintenance and upkeep of the hand hygiene stations.

In various embodiments, the system 100 also monitors hand hygiene compliance using proximity devices 103. In some embodiments, the proximity devices 103 are mounted near each patient bed 105. In some embodiments, proximity devices are mounted in hallways. In various embodiments, proximity devices are mounted both near each patient bed and in the hallways. The proximity devices 103 include radio electronics and periodically emit transmissions for reception by the radio badges 104. Upon detecting a proximity device transmission, a badge 104 records data related to the transmission including, but not limited to, an ID code associated with the proximity device, and signal strength of received transmissions. In various embodiments, the badge 104 saves the data to memory with a time stamp including the time and date. The saved data is subsequently downloaded from each badge in the system and then processed and analyzed to track hand hygiene compliance.

In various embodiments, the proximity device 103 and a badge 104 engage in a two-way communication in which the proximity device also stores data. In such embodiments, the proximity device records data including, but not limited to, an ID code associated with one or more badges within communication range of the device, signal strength of received transmissions or combinations thereof. In various embodiments, the proximity device 103 saves the data to memory with a time stamp including the time and date.

In some embodiments, proximity devices are adapted for specialized functions that differentiate one proximity device from another. For example, a room memory device is a specialized proximity device. A room memory device includes a low-power computer with sufficient memory to contain the history of room status over a period of several weeks, where room status includes information of patient presence and nature of possible patient infections. A room memory device may have data display and data entry capabilities. In various embodiments, a room memory devices is portable and can be set up or removed quickly from a room. Room memory devices can have wireless, wired or both wireless and wired network connections to interoperate with other system components. Room memory devices can be powered by a stand-alone power source such as a battery, a standard electric outlet, by energy harvested from an ambient power supply or combinations thereof. Ambient power supplies for harvesting energy can include, but are not limited to, light, heat and vibration. In various embodiments, a room memory device communicates with other transceivers, such as transceivers associated with visitors, health care workers or equipment proximate or within the room associated with the room memory device. A room memory device records interaction information for subsequent analysis in estimating disease migration. In various embodiments, the room memory device can receive information that mitigates disease migration. For example, where a room has been exposed to a contagious disease, such as a patient with Clostrididium difficile (C-diff), a health care worker assigned to clean the room can enter information indicating the room has been cleaned using a display interface of the room memory device. Such information can mitigate the probability of subsequent patients, health care workers and visitors of contracting C-diff. The information is also useful in providing an accurate simulation of disease migration.

In some embodiments, a unit memory device is a specialized a proximity device. A unit memory device includes a small computer with sufficient memory to contain the history of activity within a unit over a period of several weeks, if not months or years. In some embodiments, such activity history includes the accumulated data from room memory devices for all rooms in a unit. Unit memory devices may have data display and data entry capabilities. In various embodiments, unit memory devices are powered by standard electric outlets. Unit memory devices include wireless, wired, or both wireless and wired network connections to interoperate with other system components. In various embodiments, unit memory devices include unit displays to provide feedback to HCWs on the status of the system, their performance, or other metrics related to system objectives.

Network gateways are devices that connect other system components to other computers or networks, so that the system components may exchange information with larger information technology systems. For example, some health information useful for accurately simulating disease migration may be located on other databases outside the system. Such information may include, but is not limited to, health records of patients, HCWs, visitors, contractors, etc., and maintenance records related to instrument and room cleaning. Network gateways may also transmit service requests to other computers; such requests may offload data, request current time or configuration data, or provide remote servers statistical data concerning the other system components. In various embodiments, a unit memory device includes a network gateway. In some embodiments, the system computer includes the unit memory device.

In some embodiments, location and time anchors are specialized proximity devices. In some embodiments, a location and time anchor is a single device. A location and time anchor, either alone or in a combined device, includes small, low-power processors with sufficient computational resources to engage in wireless protocols for the purpose of identifying a location or a name of a room, and for assisting in ongoing clock synchronization. These devices may include a battery, use a standard electric outlet, use power scavenging methods (e.g. from light, heat, vibration, etc) or combinations thereof for power. In various embodiments, location and time anchors transmit unsolicited messages including location and/or time information. In some embodiments, the unsolicited messages are transmitted at a higher power than other transceiver devices such as wearable transceiver devices, for example.

In various embodiments, a proximity device can be preprogrammed to emit a beacon of wireless information at a time resolution adequate to determine movement about a facility by a badge wearer and which provides suitable badge lifetime. For example, the wireless electronics of the system can be adapted to turn on for a portion of time in a period to allow for transmissions of the proximity device and reception by the badges. This time period is adjustable for different applications. Typical considerations can include, but are not limited to, one or more of: the speed with which a badge-wearing person can migrate about the facility, the variation in signal strength experienced, conservation of the "on" time for the receivers in the badge to reduce power consumption and/or combinations of these considerations. The amount of power consumed by each badge is related to the amount of "on" time where the badge is listening for the proximity device or the actuated device (such as a hand hygiene station).

In various embodiments, the system provides a self-synchronizing function that allows for gated, periodic reception of transmissions to reduce power consumed by the wireless badges. Since all systems experience at least slight timing drift, the various badges are synchronized with the proximity device(s) near them to achieve a uniform time for devices in proximity. As badges move about the facility, these synchronizations can take place to ensure that all of the proximity devices and badges are within an acceptable timing skew to facilitate gated reception of signals. In one embodiment, at a specified interval, the badges in the system are programmed to transmit their clock information. The proximity device can differentiate the times and adopt the latest time transmitted by the badges. The badges then all adopt that time. This synchronizes the clocks of all of the badges and proximity devices. It is understood that variations can occur without departing from the scope of the present subject matter. For example, the system could adopt the earliest time to perform synchronization. Other timing approaches are possible without departing from the scope of the present subject matter.

In various embodiments, the hand hygiene stations 102 record data in memory when the station is activated. The data may include, but is not limited to, an ID code associated with one or more badges within communication range of the station, signal strength of received transmissions, status information associated with the hand hygiene station, time of day, date or combinations thereof. In embodiments where the badges, hand hygiene stations and proximity devices reciprocate communications, the system is less likely to generate erroneous data. In various embodiments, hand hygiene stations 102 include the functionality of proximity devices 103.

In various embodiments, signal strength data, whether recorded on a proximity device, a badge, a hand hygiene station or combination, is used to determine if the badge wearer entered a hand hygiene sensitive area. For example, in a hospital, a hand hygiene sensitive area 106 may include any area close enough for a person to touch a patient. In some hospitals, entering such an area requires that the person wash their hands prior to entering and immediately after exiting the area. In various embodiments, use of signal strength data from one or more devices can assist in determining violations of, or conformance to, hand hygiene protocol with respect to hand hygiene sensitive areas 106 without constant visual monitoring.

In various embodiments, the badges are adapted to communicate with each other. For example, such embodiments provide for the exchange of data 120. In various embodiments, each badge monitors the duration of badge-to- badge contact based on the amount of time the badges are engaged in wireless communication.

FIG. 2 shows a block diagram of a hand hygiene station 202, wearable badge 204, proximity device 203 and system computer 201 according to one embodiment of the present subject matter. The hand hygiene station includes wireless communication electronics 211, hand hygiene apparatus 212 and a sensor 213 to monitor the hand hygiene apparatus. In various embodiments, the wireless electronics 211 are compatible with the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. In various embodiments, the wireless electronics 211 are compatible with the IEEE 802.15 standard. It is understood that use of electronics conforming to other radio frequency wireless communication standards or custom protocols are possible without departing from the scope of the present subject matter. The hand hygiene apparatus 212 includes devices used for one or more hygiene related activities, including but not limited to, hand washing, hand sanitizing, hand drying and/or hand disinfecting. In various embodiments, the sensor 213 monitors one or more conditions of the hygiene station such as, but not limited to, dispensing of soap, dispensing of sanitizer, flow of water, dispensing of towels or tissue, level of sanitizer products used with the station, duration of sensed conditions, battery status or combinations thereof. In various embodiments, the sensor is a switch. In various embodiments, multiple sensors are employed to monitor conditions of the hand hygiene station. The wireless electronics 211 processes signals received from the sensor 213 to identify hand hygiene related activity and generate hand hygiene data related to the activity. The wireless communication electronics 211 transmits the hand hygiene data to one or more badges 204. In various embodiments, where a proximity device 203 is located within communication range of a hand hygiene station 202, the proximity device receives and records data associated with transmissions from the hand hygiene station 202.

In various embodiments, proximity devices 203 are at least located near areas where the status of hand hygiene is important or is likely to change. In a hospital setting, such locations include, but are not limited to, areas near patients and or near an access area of a patient bed or a patient room, such as the door. The proximity devices 203 include wireless electronics 214, a clock 215 and, in some embodiments, memory for storing data. In various embodiments, the wireless electronics 214 are compatible with the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. In various embodiments, the wireless electronics 214 are compatible with the IEEE 802.15 standard. It is understood that use of electronics conforming to other radio frequency wireless communication standards or custom protocols are possible without departing from the scope of the present subject matter. The proximity device 203 transmits a signal at a predetermined interval for reception by any badges 204 within communication range. Upon receiving a transmission from a proximity device 203, a badge 204 will record data associated with the transmission. In various embodiments, recording data at the badge 204 includes responding to the proximity device transmission and exchanging data with the proximity device 203. Data recorded in the memory of the badge 204 and/or the proximity sensor 203 includes, but is not limited to, signal strength of received data, data to identify the transmitting device, status information of each device or combinations thereof. In various embodiments, the badge 204 and the proximity device 203 saves the data to memory with a time stamp including the time and date. In various embodiments, the proximity devices are precisely located to provide a location anchor within a facility such that interactions recorded by either the proximity device or a portable wireless transceiver device can be used to map the movement of the portable wireless transceiver devices.

The badges 204 are worn by persons working in and/or visiting a facility that utilizes a hand hygiene compliance system. The badges 204 include wireless electronics 216 for receiving radio frequency transmissions, processing electronics 222 including a memory 217 for storing data associated with received transmissions and a clock 220 for time stamping saved data, and a power source, such as a battery 218, to provide power. In various embodiments, the memory 217 includes flash memory.

Upon subsequent analysis, the data downloaded from the badge 204 is used to track hand hygiene compliance of the badge wearer. For example, in various embodiments where a proximity device 203 is positioned near a critical area, the signal strength provides an indication of how close a badge wearer was to the proximity device 203. In a hospital setting, each patient, or patient bed may include a proximity device 203. Some hand hygiene compliance protocols require hand washing before and after a person touches or gets close to a patient. Using the stored signal strength data, the system determines when a badge 204 was close to a patient to require the person to wash their hands before and after the encounter. Further analysis of the badge data determines whether the person complied with the protocol.

In another example, where a badge 204 records transmissions from more than one stationary transceiver device within a relatively short time interval, the system determines the position of the badge 204 and tracks the movement of the badge to assess hand hygiene compliance. The probable position of the badge 204 can be derived from the relative signal strengths of each of the transmissions associated with the stationary transceiver devices.

In yet another example, where a badge transmission is recorded by two or more other devices, subsequent processing identifies the position of the badge 204 using the signal strength of the transmission recorded in the two or more other devices. The accuracy of the location depends on the accuracy of the known location of the two or more other devices. Therefore, if the two or more other devices include stationary devices such as hand hygiene stations 202 or proximity devices 203, the probable location of the transmitting badge should be quite accurate, as the system, upon configuration, should have a location identified with each of the hand hygiene stations 202 and the proximity sensors 203.

In another example, where two badge wearers are in close proximity to a hand hygiene station as it is activated, both badges receive the transmission from the hand hygiene station. In some embodiments, both badges record the hygiene related data and subsequent processing determines which badge was associated with the hand hygiene related activity. In some embodiments, for example where the badges respond to the initial hand hygiene station transmission, the station evaluates the relative strength of the received transmission signals, identifies which badge to associate with the hand hygiene activity and attenuates subsequent transmissions to isolate communication with the identified badge. In various embodiments, badges record all discernable transmissions. In some embodiments, only data associated with transmissions exceeding a predetermined signal strength threshold is saved to memory. In various embodiments, where the proximity devices and/or hand hygiene stations save received transmission data, all discernable data is saved. In some embodiments, only data associated with transmissions exceeding a predetermined signal strength threshold is saved to memory. In various embodiments, proximity devices are located in areas such as hallways and doorways to assist in monitoring badge movement associated with hand hygiene tracking. In various embodiments, configuration of the system includes mapping the communication range and signal strengths of the various hand hygiene stations and proximity devices. Such configuration data allows the system computer to process and analyze signal strength data downloaded from the badges to accurately map the movement of one or more badges and determine specific occasions of hand hygiene compliance and non-compliance. At some point in time, such as the end or a day, the end of a visit, or the end of a shift, a person wearing a radio badge 202 turns the badge in or takes care of downloading the data stored in the memory of the badge to the computer 201. For download, the badge 202 is connected to a system computer 206 to retrieve the hygiene related activity data from the memory 217 of the badge 204. The badge 204 is connected to the computer 201 using a wired connection 208, such as, a USB connection, to download the data from the badge to the computer. In various embodiments, the wired connection 208 is used to recharge the badge battery 218.

FIG. 3 shows a badge and computer according to one embodiment of the present subject matter. The badge includes wireless electronics 316, processing electronics 322 including a memory 317 for storing data associated with received transmissions and a clock 320 for time stamping saved data, and a power source, such as a battery 318, to provide power. In various embodiments, the memory 317 is flash memory. The badge 304 downloads hand hygiene related data to the computer 301 using a wireless connection 309. The wireless electronics are also used to communicate to the hand hygiene stations and the proximity devices. In various embodiments, the wireless electronics are compatible with the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. In various embodiments, the wireless electronics are compatible with the IEEE 802.15 standard. It is understood that use of electronics conforming to other radio frequency wireless communication standards or custom protocols for communicating between the badge, hand hygiene stations and proximity devices are possible without departing from the scope of the present subject matter. In various embodiments, the badge 304 includes separate wireless electronics for communicating to the computer 301. In various embodiments, the badge automatically downloads saved data anytime the badge can communicate with the system computer. In some embodiments, badges upload information from other system devices including other badges, hand hygiene stations and/or proximity sensors and transfer the information to the system computer whenever the badges can communicate with the computer. In various embodiments, the system includes one or more nodes coupled to the system computer to accommodate badge downloads.

FIG. 4 shows a badge according to one embodiment of the present subject matter. The badge 404 includes wireless electronics 416, processing electronics 422 including a memory 417 for storing data associated with received transmissions and a clock 420 for time stamping saved data, a power source, such as a battery 418, to provide power and an annunciation device 421. In various embodiments, the annunciation device 421 is activated to remind the wearer to comply with a hand hygiene protocol. For example, if the badge 404 detects that it has moved into close proximity to a patient area, then out of the close proximity of the patient area and then into close proximity of another patient area without using a hand hygiene station, the annunciation device 421 activates. In the above example, activation of the annunciation device 421 is to remind the badge wearer to comply with a hand hygiene protocol requiring hand washing between visits to different patients. It understood that a variety of annunciation devices 421 are possible for use with the badge 404 without departing from the scope of the present subject matter including, but not limited to, devices producing vibration, light, and sound. It is also understood that is possible to program the badge to use the annunciation device to alert the wearer to other conditions without departing from the scope of the present subject matter.

Implementation of a hand hygiene compliance system according to the present subject matter improves hand-cleaning compliance and reduces the risk of spreading contamination among people or equipment within a facility. The use of wireless communications allows for easy installation of a hand hygiene compliance system in an existing facility. Wireless communication reduces the need for wired infrastructure to support the system. For example, in various embodiments, wireless communication-enabled badges store and download all the pertinent information, thus the hand wash stations and proximity devices are not required to be directly networked to the system computer. In various embodiments, the components can include an independent power source, such as a battery for example, thus reducing installation costs associated with providing additional outlets. In some situations, a facility need only replace existing hand wash stations with, battery powered, wireless communications enabled, hand wash stations to complete the installation of a system. In various embodiments, existing hand wash stations are easily modified to incorporate the one or more sensing devices and wireless electronics.

FIG. 5 shows a flow chart of a method 530 for detecting hand hygiene data in a hand hygiene compliance system according to one embodiment of the present subject matter. The method 530 includes detecting hand hygiene activity at a hand cleaning station 531, transmitting data related to the hand cleaning station 532, receiving the data at a radio badge 533, and measuring the signal strength of the received data 534. FIG. 6 is a flowchart of a method for collecting hand hygiene data in a hand hygiene compliance tracking system according to one embodiment of the present subject matter. The method includes detecting hand hygiene data 630, saving the data to memory of a radio badge 641, detecting and saving additional hand hygiene data until collection period is complete 642, download data to a computer 643 and processing the data to determine compliance to hand hygiene policy 644. In various embodiments, hand-cleaning data is recorded each time the badge is associated with hand cleaning activity at a hand cleaning station. In various embodiments, the collection period ends at a predetermined time, such as for example, the end or a day, the end of a visit, or the end of a shift. At the completion of the collection period, the badge is connected to a system computer to retrieve the hand cleaning data from the memory of the badge and clear the badge memory for another collection period. In some embodiments, the data is then analyzed to determine hand hygiene compliance. In various embodiments, the system depends on time stamps to determine event sequences related to hand hygiene tracking. In some embodiments, precise timing coordinates communication events between devices. For example, in some embodiments, energy conservation is important to the robust operation of the system and one way to conserve energy is to limit wireless communications. Thus, the devices adhere to a precise schedule such that data is transmitted when the intended receiving devices, such as the badges for example, are enabled to receive wireless transmissions. FIG. 7 shows a flowchart for a method 750 to extend the battery life of a badge by limiting the availability of wireless communications in a badge. The method includes saving a transmission schedule to the badge memory 751, synchronizing the badge clock according to the schedule 752, enabling the wireless electronics according to the schedule 753, disabling the wireless electronics according to the schedule 754, and repeating the schedule 755. In some embodiments, the wireless electronics are enabled longer than they are disabled. In some embodiments the wireless electronics are enabled as long as they are disabled, thus extending the battery life. In some embodiments, the transmission schedule enables the wireless electronics for a fraction of the time they are disabled, thus extending the battery life even further. Reducing the time the wireless electronics are enabled conserves energy but burdens the devices to adhere to a precise schedule for Communications. Devices with such a precise schedule rely on clocks that are synchronized which the clocks in the other system devices.

FIG. 8 illustrates a flowchart of a method 860 for synchronizing a device clock within a system according to one embodiment of the present subject matter. The method includes transmitting synchronization data from the device at a predetermined time 861, receiving synchronization data from one or more other devices 862, and resetting the device clock based on the received data 863. In various embodiments, the synchronization data includes the value of the device clock at the predetermined time. The received data includes the synchronization data from the other devices. In some embodiments, the device's synchronization data is compared to the received data and the clock is reset according to the highest clock data. In some embodiments, the device's synchronization data is compared to the received data and the clock is reset according to the lowest clock data. It is understood that other criteria for resetting the clock using the received synchronization data is possible without departing from the scope of the present subject matter. In various embodiments, the hand hygiene stations synchronize their clock with the badges and emit their synchronization data according to the same predetermined time. In some embodiments, the proximity devices synchronize their clock with the badges and emit their synchronization data according to the same predetermined time. In some embodiments, the proximity devices and the hand hygiene stations synchronize their clocks with the badges and emit their synchronization data according to the same predetermined time. In various embodiments, one or more devices emit their synchronization data with higher power than transmissions associated with other hand hygiene tracking events.

As discussed above, collecting signal strength data allows the system to track badge movement and estimate hand hygiene compliance of the badge wearer based on the movement and corresponding hygiene related data. For example, if during the course of a shift, a badge records a number of transmissions from hand hygiene stations, proximity sensors and/or other badges, the identity of these devices, their location and the signal strength data can be processed to determine the movement of the badge, thus, the wearer, throughout the shift. If the movement shows the badge entering and exiting hand compliant sensitive areas but there is no corresponding hand hygiene related data indicating the wearer washed their hands, the system can estimate the wearer of the badge was not in compliance with a hand hygiene protocol requiring hand washing before and after entering hand hygiene sensitive areas. It should be noted, in various embodiments, such as, where proximity sensors and/or hand hygiene stations save received transmission data or embodiments where other badges receive and save transmission data whether related to that particular badge or not, that even if a badge was defective and not collecting data, the movement of the defective badge and hygiene related data can be determined from data collected about the badge from data stored on the other devices including hand hygiene stations, proximity devices and/or other badges that received and recorded transmission related to the defective badge. FIG. 9 is a flowchart of a method for estimating hand hygiene compliance of a badge wearer according to one embodiment of the present subject matter. The method includes receiving a plurality of signal strength data related to a badge from one or more system devices 991, receiving hand hygiene activity data related to the badge from one or more system devices 992, mapping the badge position and hand hygiene activities with respect to time 993 and comparing the map of badge movement and hand hygiene activity with to a predetermined hand hygiene protocol to estimate hand hygiene compliance of the badge wearer 994. In various embodiments, the signal strength data and hand hygiene activity related data is received from the badge. In some embodiments, the signal strength data and hand hygiene activity related data is received from a device other than the badge. In some embodiments, the signal strength data and hand hygiene activity related data is received from a group of devices including the badge. In some embodiments, the signal strength data and hand hygiene activity related data is received from a group of devices not including the badge.

In some embodiments, badges are enabled to communicate (broadcast and receive signal strength messages) with other badges as well as with the wireless transceiver devices placed in specific locations (e.g., patient rooms, nurses stations). In addition to assigning wireless transceiver devices to healthcare workers, either as a badge or in a different form, they can also be given to patients, visitors, suppliers, contractors or other persons or equipment allowed on-site. The system measures the duration and approximate location of interactions between the badge wearers, such as between different healthcare workers, between patients and healthcare workers, and between different patients, for example. In various embodiments, visitors are assigned badges, or a wireless transceiver device in some other form, such that interactions with the visitors are measured. The portable nature of the wireless communication devices allows rapid deployment of a system for either temporary or permanent use.

In various embodiments, the system computer receives health related information about the entities associated with the badges, the hygiene stations and the proximity devices. For example, the system computer can receive health related information about a person associated with a wearable badge, including a medical history. Such information can include information about diseases the badge wearer has recently been exposed to, diseases the badge wearer currently is infected with, inoculations the wearer has received that can mitigate the wearer's ability to contract or transmit a disease, or combinations thereof. Additionally, the system computer can receive information associated with the facility and the equipment within the facility that can be useful in tracking disease migration. For example, a proximity device or badge can be associated with a room or a piece of equipment. The system computer can receive history information associated with the room or piece of equipment. For example, if a patient contracted C-diff, proper cleaning of the room and equipment used in proximity with that patient is important to efficiently preventing the spread of C- diff to other persons who may use the room or contact the equipment used to treat the patient. Thus, where a room or a piece of equipment is used to treat a patient with a contagious disease, information about how that room or equipment is cleaned can be pertinent to accurately estimating disease migration. In various embodiments, the system computer can receive the room or equipment history information from a number of sources including, but not limited to, analysis of collected interaction information, one or more other databases, other proximity or mobile devices or a combinations thereof. In addition to measuring hand hygiene, the present subject matter enhances other patient-safety-and-quality activities. For example, a deployment of a system as described above allows hospital epidemiologists to do rapid contact tracing to investigate infectious disease outbreaks. For example, the system includes information to trace interactions and movement of patients and healthcare workers exposed to equipment, rooms and other people associated with a contagious disease. In embodiments where equipment is monitored, the system can trace interactions and movements of patients and health care workers exposed to equipment that has been used to treat, or simply exposed to, a contagious disease. In embodiments where rooms are monitored, the system can trace interactions and movements of patients and health care workers using a room that has been used to treat a patient having a contagious disease or had been entered by a person known to be infected with a contagious disease.

In the setting of an infectious disease outbreak, such information can allow officials to know exactly which healthcare workers came into close contact (e.g., 3 - 6 feet) or direct contact with other healthcare workers, patients or other badge wearer, for given period of time. Such information can expose the history of people infected with contagious or communicable conditions, but before such conditions or symptoms are recognizable. Such diseases include, but are not limited to, severe acute respiratory syndrome (SARS), influenza, mumps, lice, chickenpox, strep, Clostrididium difficile (C-diff), Methicillin resistant S. aureas, or combinations thereof. As a result, the system can further identify current infected-but-asymptomatic healthcare workers, patient and visitors who could spread disease or continue to spread the disease unintentionally. Such information can allow officials to act to notify potentially infected people such that steps can be taken to avoid further migration of the disease. Thus, if contact tracing is done early enough to enable the rapid isolation or treatment of exposed patients, it reduces the spread of an outbreak within healthcare facilities or other facilities utilizing the system. Badge-to-badge communications allow for more precise tracking of person-to-person exposure. Such a system can be adapted to identify the identity of a person whose proximity or contact history has been tracked, to provide a title associated with the person (for example, "patient," "doctor," "nurse" titles may be associated with the person in contact to anonymize data if preferred), and/or to completely render the identity of the person anonymous (for example, the patient was in contact with 3 other people at the facility). It is understood that other variations are possible without departing from the scope of the present subject matter. Thus, the system can provide programmable levels of anonymity in various embodiments. Wireless-enabled, contact tracking identifies healthcare workers, patients or other personnel, who may have a contagious condition, earlier than current methods (e.g., inquiring or inferring contacts based on work schedules). Wireless-enabled contact tracking reduces the spread of outbreaks within a facility including, but not limited to, hospitals, long-term care facilities, and outpatient settings. In non-outbreak settings, a wireless-enabled contact-tracing approach is used for training and teaching purposes to improve infection control practices. With data generated from personnel wearing wireless transceiver devices, such as badges, during a normal working day, infection control staff are able to demonstrate how many patients and other healthcare professionals could have been infected if someone had decided to work while ill. Hand-hygiene practice can also be measured during such drills to demonstrate missed opportunities to protect patients and other healthcare workers.

In various embodiments, wireless-enabled contact tracking is used to measure healthcare quality by recording the length of interactions between healthcare providers (i.e., nurse, physician) and patients. For example, hospital administrators are able to measure how long patients spend in waiting rooms or unattended in clinic rooms compared to how long they spend actually talking or interacting with healthcare providers. Such measurements, available in near-real time, serve to increase the efficiency of healthcare visits. In a hospital setting, wireless-enabled contact tracking increases patient safety. For example, there have been reports that patients in contact isolation receive less care (fewer interactions with healthcare providers) because contact isolation policy requires healthcare workers to wear gowns and gloves before entering a contact isolation room. With healthcare workers wearing wireless badges, and wireless transceiver devices assigned to patient rooms (or directly to patients), hospital managers can measure how long patients in contact isolation spend with healthcare workers compared with patients not in contact isolation who have similar patient conditions. In various embodiments, a system according to present subject matter can be deployed without reliance on a grid-powered infrastructure. In some embodiments, low-level communication protocols of the transceivers can be peer-to-peer, ad hoc, or personal area networks (PAN) that support direct data communication between any of the system components described previously, without the need for infrastructure supplying power, repeaters, or even the establishment of a mesh network control structure. When one component is near enough to transmit data to another component, and also to receive data from that component, the two components "see" each other. In various embodiments, two components see each other when they are in close enough proximity for the low layer wireless protocol to function. In various embodiments, the transceivers of the system do not necessitate "pairing" or other credentials as a prerequisite for communication. Such security and integrity features may optionally be employed. In various embodiments, the transceiver devices include four internal service protocols, layered above the (possibly standardized) wireless communication protocol, enable subsequent relay, aggregation, processing and control of data in the system. These four services are synchronization, location, history exchange, and device status. Each of these four services defines message format, specifies timing and reliability needs, and entails operational considerations to control, maintain, and monitor the service.

The synchronization service provides each device access to a virtual clock. Two properties of the virtual clock are that it advances at the same rate as real time and that any two devices in the deployment which access their virtual clocks observe the same clock value. In some embodiments, the value of a virtual clock coincides with accepted standard clocks (Universal Coordinated Time, for instance); in other embodiments, the virtual clocks may be set to some internal clock standard. The virtual clock service may be implemented by periodic exchange of messages between devices, or may be implemented by some assisting infrastructure (such as WWVB, NTP or other standard mechanism). In the case of periodic exchange of messages to establish and maintain the virtual clock service, the protocol is opportunistic, such that, system components exchange messages with other components that are within wireless communication range. In various embodiments, proximity sensors that function as location and time anchors are either within range of each other or, with high probability, are periodically within range of wearable devices that bridge connectivity gaps and thus provide acceptably frequent resynchronization between components. The location service is provided by proximity sensors functioning as location and time anchors, though other non-mobile components can also provide this service in some embodiments. Each component that supports the location service is programmed with a location designation, either an abstraction (such as room name or unambiguous object placement) or with spatial coordinates of the placement of the component. This programming can be done prior to deployment, at the time of deployment, or in- field if the component can be relocated dynamically. In some embodiments, the location service operates in "push" mode, that is, the components periodically transmit (broadcast) location messages to any receiving component within range. The location messages can include, but are not limited to, the location identity, location abstraction or the coordinates of the transmitting component. In other embodiments, the location service operates in "pull" mode where a requesting component transmits (broadcasts) a location query message to all components within range, and any provider of the location service responds to the query with a location message. Location queries and location messages may be attenuated in transmission power, to enable greater accuracy of inferring location by receiving units; alternate radio frequencies may also be employed, and other technologies for range finding can also be used including, but not limited to, infrared signals and ultrawide band ranging.

Wearable devices can approximate current location based on the history of location messages they receive, taking into account received signal strength information or other characteristics of the messages they receive which contain location information. Wearable devices have sufficient computational power to analyze maps of the deployment region, perform calculations on the history of recently received messages, and to approximate a probable current location.

The history exchange service enables components within wireless range to exchange recent history of events recorded by the components. Using a history exchange service enables one component to assemble a view of the combined histories of other components that it has recently seen. Such a view makes possible computations about disease transmission metrics within the component. History exchange messages can be pull mode or push mode; in some cases, the information exchanged between two components will use several messages, because low-layer data protocols have size limitations on the payloads of packets or frames.

Device status service supports diagnostic reporting and control of the components. For deployments with non-mobile components, such as time and location anchors, room memory devices, unit memory devices, and so forth, typical management of the components involves knowing the status of the components including, but not limited to, current battery level, ratio of successful to unsuccessful communication, and which communication links are most reliable. In deployments with gateways connected to traditional networks, administrators could remotely inspect the current status of the deployment's components by querying the gateway; the gateway would aggregate the status of components on an ongoing basis by periodically using the device status service.

The mechanism of disease migration on a macro scale (as opposed to microbiologic mechanism) is briefly mentioned above. The event of infection, that is, the transfer of disease from one individual to another, is generally described statistically such that there is a potential of infection by exposure, such as contact or breathing droplet-laden air, but infection is not certain. The exposure potential can depend on many factors (susceptibility of individuals, history of mitigation events, cumulative contact with many infected individuals, virulence of infecting agents, etc.). Given a history of individual movement, proximity or contact between individuals, and mitigating events, it is possible to construct a model of how disease may spread. These models can be analytic (mathematical) or approximations generated by simulation. For analytic models and similar simulation methods, two kinds of result are sought, forward results and backward results. Forward results are quantities calculated by running a simulation forward in time; backward results are quantities calculated by running a simulation backward in time. Forward or backward results can be projected to individuals or groups of individuals such that the potential quantities can include, but are not limited to, probabilities of having been infected (forward) or probabilities of being initially infected (backward).

Simulations depend on scenarios of contact between individuals and spatial and temporal configurations (movement of HCWs, etc). The choice of scenario can be artificial (say by random number generation conforming to statistical models previously obtained that characterize valid ranges of choice), or the scenario can be a replay of actual movement and contact history from a clinical study or combinations thereof. Simulations can also be hybrid simulations, where the scenario choices are fed into the simulation in real time, as they are observed by instrumented hospitals and clinics, such as are described in this document. One other choice of simulation is whether to calculate probabilities, in the style of analytic models, or to randomly choose outcomes during the simulation (so-called Monte Carlo methods), where the random choices are governed by probabilities of infection, contamination, and disease duration. The results of these simulations can be lists of infected individuals and contaminated rooms. In addition to the results of simulation (be they probabilities or simulated infection outcomes), simulations can also be used to uncover patterns of behavior and structural observations on the nature of how disease may spread. For example, it can be that one area in a hospital exhibits higher contagion than another area, or it can be that one shift in a clinic has lower infection rates than another. The running of the simulation is repeatable, being derived ultimately from deterministic computation, and patterns (based on scenarios, spatial, temporal, and initial configurations) may be studied and understood. Finding and understanding these patterns is a key to improving healthcare processes. The present subject matter provides that these simulations can be implemented distributively, computed on the same devices that record contacts, mitigating events, and movement within a health care facility such as a hospital or clinic, without the need for a permanently installed computing infrastructure. For the system of components and protocols described in this document, simulations and models can be computed distributively in each device, or the event and contact data can be uploaded to traditional information systems for later analysis and simulation, or both computed distributively an uploaded for later analysis and simulation. Simulations and models computed in each device collectively can be referred to as distributed infection models.

FIG. 10 includes a flowchart of a method to estimate a probability of infection according to one embodiment of the present subject matter. The method 1000 includes associating a transceiver device with an entity 1001, receiving health information of the entity 1002, recording interaction information of interactions of the transceiver device with other transceiver devices 1003, and estimating a probability of infection using a simulation based on the recorded interaction information and the health information 1004. In various embodiments, the recorded interaction information includes interaction information related to mitigating disease migration including, but not limited to, interaction information from a hygiene station, health information from a room memory unit indicating a recently cleaned room, health information from a transceiver device associated with a person having an active inoculation to a disease or combinations thereof. In some embodiments, the estimated potential for threat of infection or condition of infection is derived from one or more simulations using the recorded interaction information and the health information. In some embodiments, transceiver devices process local simulations using interaction information and health information collected by the transceiver. Local simulation can be used to estimate potentials of infection for the entity associated with the transceiver device. In some embodiments, a potential for infection exceeding a threshold value will trigger an annunciation device of the transceiver device. An entity alerted to a potential for infection exceeding a threshold can then take mitigating action to reduce the potential. In some embodiments, the potential for infection may be a probability of infection of a specific disease. In various embodiments, the potential for infection may be an overall probability of infection of a number of specific diseases the system is configured to track. In various embodiments, the potential may include a probability of being infected, a probability of infecting someone else, or both. In various embodiments, the potential for infection may be represented by using outcomes other than probabilities including, for example, a binary outcome, a range of discrete outcomes or a combination thereof. In various embodiments, the system is used for training and research purposes. For example, where a contagious disease outbreak has occurred, collected interaction data can be used to research better practices to prevent such an outbreak to reduce the ability of the disease to migrate. Such research uses the system to perform simulations using the collected interaction data to understand the actual disease migration. Additional simulations can introduce new interaction information or alter the collected interaction information to investigate ideas to prevent future outbreaks. Such simulation may include moving hygiene stations, placing additional hygiene stations, changing sterilization protocols, changing hygiene protocols or combinations thereof. The system simulations using the collected interaction data can illustrate the importance of hygiene compliance in reducing the ability of a disease to migrate. For example, collected data can be altered in various training simulations to illustrate and compare the effects of good hygiene practice and risky hygiene practice in mitigating disease migration. In some embodiments, the simulations are set-up as an interactive game to give a trainee hands-on experience in understanding what hygiene practices are most effective in protecting themselves from contracting or spreading one or more contagious diseases, especially in a health care environment. Calculating simulations can also assist in identifying conditions that affect disease migration. Such conditions include, but are not limited to, identifying risky behavior that may assist disease migration, identifying opportunities for intervention and mitigation of disease migration, identifying patterns of risky, non risky and mitigating behavior of individuals, indentifying risky, non-risky and mitigating group behavior,

Risky behavior includes behavior that is more likely to spread disease, fail to contain disease, or become infected than would nonrisky behavior. Classification of what is risky is based on thresholds for probability of being infected or contaminated. Generally, probabilities are obtained from the models outlined above. However, rather than using a complete simulation, a local model can approximate probabilities within a wearable unit. The combination of local history of contact and path information obtained from other wearable units, room memory units, location and time anchors, and the combined recent history of direct contact and indirect contacts enables simulation based on interaction information (spatial and temporal). This interaction information includes enough information to approximate probabilities of infection. For example, individual A with a wearable device comes into range of individual B, who recently visited a room with an infected patient but did not engage in mitigating hygiene measures. The history of B can be available to A by the history exchange protocol. Probability factors assigned to each point in a chain of contact to enable an estimation of the probability that A is infected via B and B's contact with infection. Taking the totality of A's contacts into account is the basis for an overall calculation of probability of infection. For the scenario of A and B, risky behavior can be said to occur if the probability of infection rises above a given threshold.

Opportunities for mitigation occur after potential contact with infected individuals or contaminated areas, and when the probability of infection rises above some threshold. These opportunities can be identified on wearable devices. Such observations can trigger alerts on the wearable devices or be relayed to other components (room or unit memory devices). Intervention opportunities can be observed when a combination of individual probabilities in a unit (ward, clinic, etc) rise above some threshold, and this can be detected from data in a unit memory device or gateway.

The discussion above on Distributed Infection Models explains how simulations can enable the detection of patterns of behavior or other systemic factors (architecture, workshift schedules) that encourage or discourage infection. Patterns of individual behavior can also be approximately identified based upon local models, within wearable devices, room memory, unit memory devices or combinations thereof. If individuals generate high probability of infection repeatedly, this fact can be recorded or transmitted for subsequent analysis. Similarly, if individuals have abnormally low infection probability, then that fact can be recorded and later be studied. Beyond identification of singular risky behavior, systemic patterns or team patterns can be extracted from unit statistics. One advantage of this metric is that individual behaviors can be hidden from reporting of group behaviors. In situations where privacy of HCWs or patients is a concern, the identification of problems and potential method of mitigation can be reported without attributing the problems to specific individuals. In cases of system patterns or team behaviors, problems of infectious disease spreading may not be due to individual action, which is orthogonal to identifying specific individual behavior that encourages or discourages disease migration.

This application is intended to cover adaptations and variations of the present subject matter. It is to be understood that the above description is intended to be illustrative, and not restrictive. The scope of the present subject matter should be determined with reference to the appended claims, along with the full scope of legal equivalents to which the claims are entitled.

Claims

What is claimed is:

1. An apparatus, comprising: a portable transceiver device including a radio, memory, and a power source, the device configured to communicate with one or more other transceiver devices, wherein the portable transceiver device is configured to use the radio and memory to detect and record a history of proximity to the one or more other transceiver devices, the portable transceiver device further comprising at least one processing component adapted to receive information pertaining to disease exposure associated with the portable transceiver device or the one or more other transceiver devices, the processing component programmed to calculate an exposure potential to a contagious disease threat or condition using the history of proximity.

2. The apparatus of claim 1, further comprising an annunciation component configured to activate when the exposure potential exceeds a threshold.

3. The apparatus of claim 2, wherein the annunciation component is configured to vibrate when activated.

4. The apparatus of claim 2, wherein the annunciation component is configured to generate a sound when activated.

5. The apparatus of claim 2, wherein the annunciation component is configured to illuminate when activated.

6. The apparatus of claim 1, wherein the processing component includes executable instructions adapted to process a simulation of disease migration to calculate the exposure potential using the history of proximity.

7. A system comprising: a computer to receive health information; one or more transceiver devices; a portable transceiver device comprising: a wireless transceiver configured to communicate with the one or more transceiver devices; memory configured to record the interaction information and to receive the health information from the computer; and a processor component configured to generate interaction information related to each communication with the one or more transceiver devices, wherein the processor component is further configured to calculate an exposure potential to a contagious disease threat or condition using the interaction information.

8. The system of claim 7, further comprising an annunciation component configured to activate when the exposure potential exceeds a threshold.

9. The system of claim 7, wherein the processing component includes executable instructions adapted to process a simulation of disease migration to calculate the exposure potential using the history of proximity.

10. The system of claim 7, wherein at least one of the one or more transceiver devices includes a hygiene device comprising: a hygiene device radio; hygiene device memory; a hygiene processing component; and a sensor configured to sense a hygiene event and to trigger communication with the portable transceiver device or one or more devices, wherein the hygiene processing component is configured to generate hygiene interaction information related to triggered communication, to transmit the hygiene interaction information using the hygiene device radio and to save the hygiene interaction information using the hygiene memory.

11. The system of claim 10, wherein the portable transceiver device is configured to wirelessly receive the hygiene information from the hygiene device and to calculate an exposure potential to a contagious disease threat or condition using the hygiene information.

12. The system of claim 7, wherein at least one of the one or more transceiver devices includes a room device comprising: a room device radio; room device memory; and a room device power source configured to power the room device radio; wherein the room device is configured to use the room device radio and room device memory to detect and record a room history of proximity to the portable transceiver device, the room device further comprising at least one processing component adapted to receive room history information pertaining to disease exposure associated with the room device.

13. The system of claim 12, wherein the processing component of the room device includes executable instructions adapted to calculate an exposure potential to a disease threat or condition using the room history of proximity and the room history information.

14. The system of claim 12, wherein the room device power source is configured to scavenge energy from at least one of light, heat or vibration.

15. The system of claim 7, wherein one or more of the one or more transceiver devices includes a time anchor comprising: a time radio configured to wirelessly transmit time information, wherein the portable transceiver device further comprises a clock, and wherein the portable transceiver device is configured to receive the time information and to synchronize the clock using the time information.

16. A method comprising: wirelessly receiving health information at a portable first transceiver device; detecting one or more second transceiver devices proximate the portable first transceiver device using wireless communications; recording a history of proximity of the one or more detected second transceiver devices in a memory of the portable first transceiver device; and calculating an exposure potential to a disease threat or condition using the history of proximity and the health information, wherein the calculating is done using a processing component of the portable first transceiver device.

17. The method of claim 16, wherein detecting one or more second transceiver devices includes detecting a received signal strength of the one or more second transceiver devices.

18. The method of claim 17, wherein recording a history includes recording the received signal strength value.

19. The method of claim 16, wherein recording a history includes recording a time stamp.

20. The method of claim 16, further comprising activating an annunciation device of the first portable transceiver device if the exposure potential exceeds a threshold value.

21. The method of claim 20, wherein activating an annunciation device includes generating a vibration.

22. The method of claim 20, wherein activating an annunciation device includes generating a sound.

23. The method of claim 20, wherein activating an annunciation device includes illuminating an indicator.

24. The method of claim 16, further comprising receiving at the computer the history of proximity recorded in the memory of the first portable transceiver device from one or more of the detected second transceiver devices.