Health Applications of Wireless TechnologyMonitoring and Improving Patient Flow

Presented by Katherine ChengLi

Presentation Overview

• Introduction• Technologies Used• Wi-Fi Positioning Systems– Wi-Fi Fingerprinting– Wi-Fi Triangulation

• Ekahau’s RTLS• Patient Flow Monitoring• Conclusion

Introduction

• Wireless technologies used in healthcare– WiMAX, WLAN, WPAN, WBAN, RFID

• Monitoring bodily functions– ECG, blood oxygen level, blood glucose, coagulation,

body weight, heart rate, EMG, oxygen saturation, etc.• Accessing information wirelessly• Entering information wirelessly• Monitoring movement of entities

WiMAX

• Strong security wireless data transmission• Long distance range -> up to 50km• High data rate -> up to 70Mbps• High mobile capacity -> up to 150 km/h• Great choice for telemedicine– Image transfer

• Strong QoS framework– Prehospital management systems

WLAN

• Standard IEEE 802.11 which is well developed• Transmission of media• Communication between hospital departments or

hospital to hospital• Transfer of patient data around the hospital• Used widely in telemedicine and

healthcare data transmission

WPAN

• WPANs are mostly used for continuous patient monitoring and wireless-integrated medical devices

• Bluetooth has been popularized by Ericsson• Bluetooth has been designed for cable replacement

and short distance ad-hoc connectivity• Zigbee is an ultra-low power and low data rate

technology• Zigbee for monitoring and controlling applications

WBAN

• Zigbee or UWB standard• For low-power integrated circuits,

wireless communications, and sensors• Goal is a body integratable network• Used for computer-assisted rehabilitation

RFID

• As seen in class• Used to monitor entities like patients or equipment• Can be used to keep track of inventory but also

positioning• Can act as sensors (vital signs)

Wi-Fi Fingerprinting

• Involves taking measurements at key places to fingerprint each location

• Measurement of 4 orientations or more is suggested for every measured location for better results

M. Quan, E. Navarro, and B. Peuker, "Wi-Fi localization using RSSI fingerprinting," 2010.

Wi-Fi Triangulation

• Use of the (RSSI) received signal strength intensity of three access points

• Used to find the incenter of the triangle which indicates the position of the entity to locate

• Theoretically very precise but in practice, signal measurements are very noisy

• Needs at least three signals

What is an RTLS?

• Real-time location system• System in which tagged entities, for example by

RFID tags, continuously transmit their location• Needs transmitters and receivers• Transmitters are on the entities that need to be

tracked• Receivers are throughout the place in which the

entities need to be tracked• The location of the entities can be determined by the

system according to its own algorithm

Ekahau’s RTLS

• Uses RFID over Wi-Fi• Uses established methods like fingerprinting and

triangulation• Integrates probabilities instead of deterministic

values by assuming that measured values are noisy• Model is based on Bayes theorem where P(L|O) is

the probability of observing said entity at location L:

Ekahau’s RTLS (cont.)

• Constructs area-specific Positioning Model• Each sample point has its own received signal strength

intensity (RSSI)• Establishes legal and illegal paths• Navigation routes are embedded• RSSIs are normalized and errors are minimized by Ekahau’s

own algorithm

Ekahau’s RTLS (cont.)• Access points are used to

improve the estimates of the entities’ lcoations

• The greater the number of overlapping access points, the better the measurements

• “Dummy” access points can be used to improve the location estimation

• Although it uses the existing Wi-Fi infrastructure, the RTLS should not affect the network’s traffic

http://www.enterprisenetworkingplanet.com/netsysm/article.php/3893301/Free-WiFi-Stumblers-Do-the-Work-But-Save-You-Money.htm

Patient Flow Monitoring

• Integrate RTLS and Business Process Management• Technology to monitor service time and wait times in a

Care process (clinical pathway) • e.g. a heart attack patient arrives in ER, and the steps

followed to arrive at “balloon” operation to save the patient and eventually lead to discharge

• Track location information using wireless smart sensors

• Receive events from BPM to know what the next step in the care process is

ArchitectureEkahau’s RTLS + iPads + IBM BPM and CEP

Complex Event Processing (CEP)

• CEP lets us infer complex events by correlating the location and business process events received

• Patient Flow Monitoring used an algorithm based on rules that depended on the order of the events processed to determine patient flow through a care process

• A state-based algorithm has been developed to follow a process based on service states and wait states to simplify the processing of events and optimize patient flow monitoring

References

• L. Peyton, A. Mouttham, K.A. Ali, A. Baarah, H.T. Mouftah, “Real-time Analytics and Quality of Care”, Handbook on Systems and Complexity in Health. Springer, pp 495-519, 2013.

• S. Baffoe, A. Baarah, L.Peyton, “Inferring State for Real-Time Monitoring of Care Processes”, Software Engineering in Healthcare, San Francisco,2013

• Aladdin Baarah, "An Application Framework for Monitoring Care Processes“, PhD Thesis, 2013.

• Renaud T. Bougueng, "Location-Aware Business Process Management for Real-time Monitoring of Patient Care Processes“, M.Sc. Thesis, 2013.

Patient Flow Monitoring (events)

Cardiac Care Process (State Model)

Rule Patient State MappingRules which Transition Patient State Inferred Patient StateCurrent Patient State Source Event(s) Event

SourceTriaged PatientIn RTLS Wait for Phys. Initial

Assess.Wait for Phys. Initial Assess.

PhysicianIn RTLS In Phys. Initial Assessment

In Phys. Initial AssessmentWait for Tests

PhysicianOutTests Completed

RTLSBPM

In Bed ED

Wait for Tests Tests Completed BPM Wait for Phys. Re-assessment

Wait for Phys. Re-assess. PhysicianIn RTLS In Phys. Re-AssessmentIn Phys. Re-Assessment PhysicianOut

OrderBedBed Not Available

RTLSBPMBPM

Wait for Bed CW

Rules Algorithm vs State Algorithm

• Events are triggered via monitoring done by the wireless devices

Rules Only StatesTakes into account the order of events that have occurredLinearHigh number of rulesNot flexibleDifficult to change the rules to infer new milestones in the process

Milestones are reached when a number of conditions have been metDecreased complexity of rulesFlexibleNew states are easy to add and remove, and intermediate events as well

Healthcare Application Inferred Rules

• By tracking movement, it is possible to infer some events

• Permits tracking times• By tracking times and movements, and recording

when they occur, it is possible to make an analysisand determine where the process needs to beimproved

Care Process Monitoring Dashboard

Conclusion

• RTLSs are very useful for areas like healthcare monitoring

• Location algorithms can still be improved• There is great potential for these kinds of systems to

improve current processes

Question 1 – Triangulation (1/3)

Triangulation is one of the basic methods used to localize an object indoor. In the diagram above, assuming that R, S, and T represent routers or access points and that the lines coming from R, S, and T are the received signal strengths, what steps do we have to follow to find the (x,y) coordinates of K (the location we are trying to find) ? Use the diagram above and the equations to help you describe the steps needed and the resulting equations.

K

Question 1 – Triangulation (2/3)

Answer: To find the coordinates of K we have to:1. Find the equation of each line of received signal strength. (A line can be

symbolized by the equation y = mx + b where m is the slope and b is the y-intercept of the line) The slope of the line and the y-intercept can be found using the angles given by the received signal strengths to the routers and the coordinates.

2. Using the line equations, we can determine the coordinates of A, B, and C by using simple substitution of the intersecting lines for each point.

K

Question 1 – Triangulation (3/3)

Answer: To find the coordinates of K we have to: (cont.)3. With the coordinates of A, B, and C, and Pythagoras’ theorem, we can find the

lengths of AB, BC, and AC.4. With the lengths of AB, BC, and AC, as well as the coordinates of A, B, and C, we

can apply the equations above to find the incenter of the triangle which is the coordinates of K.

K

Question 2 – Rules vs States

• In healthcare, it is useful to monitor events in order to gather metrics and analyze them. Two algorithms were presented to monitor processes and know at which stage they are: an algorithm based on rules, and an algorithm based on states. Why is an algorithm based on states better than an algorithm based on rules when considering flexibility?

• Answer: An algorithm based on states is better because it is easier to add, modify, or remove events on which states might be dependent on. In the rules algorithm, this would imply the modification of several rules and a much higher complexity than the states algorithm.

Question 3 – Hospital Monitoring

• Ekahau is a real-time location system(RTLS) that uses several methods to monitor events. An RTLS in a hospital is interesting because we can gather important metrics from it and execute an analysis to see where the gaps are. Why does the Ekahau RTLS uses probabilistic values instead of deterministic values in their algorithms? How is that reflected in a hospital’s environment?

• Answer: Ekahau uses probabilistic values because measurements are noisy and depend on the environment. This is reflected in a hospital’s environment due to the traffic, the various equipment they use, the hospital’s layout etc.