SIP-based Medical Event Monitoring System Knarig Arabshian and Henning Schulzrinne Department of Computer Science Columbia University {hgs, knarig}@cs. columbia. edu June 6, 2003
Overview n n n Basics of SIP (Session Initiation Protocol) Details of SIP event notification architecture Medical Logic Modules and SIP XML Messages and SIP Benefits Conclusions
SIP-based Medical Event Monitoring System n n Medical industry transitioning to Internetbased communication SIP can work on a variety of devices Adopted as protocol of choice for third generation wireless networks Used for Internet conferencing, telephony, presence, event notification and instant messaging
What is SIP? n n n The Session Initiation Protocol (SIP) is a signaling protocol used for establishing sessions in an IP network. SIP is part of the IETF standards and is modeled upon other Internet protocols such as SMTP (Simple Mail Transfer Protocol for e-mail) and HTTP (Hypertext Transfer Protocol for www) SIP is also being used in Microsoft Messenger in Windows XP A session could be a simple two-way telephone call or it could be a collaborative multi-media conference session. Different services are possible n Internet telephony n Instant Messaging with buddy lists n Event notification n Device control
What is SIP? n n n Two Components within SIP: User Agent and the SIP Network Server. User Agent is the end system component for the call The User agent can be both a User Agent Client (UAC) and a User Agent Server (UAS) The client element initiates the calls and the server element answers the calls. SIP Server is the network device that handles the signaling associated with multiple calls.
What is SIP? n n Main function of the SIP servers is to provide name resolution and user location Caller is unlikely to know the IP address or host name of the called party Caller will dial an email-like address or a telephone number associated with the called party. A SIP proxy server receives requests, determines where to send these, and passes them onto the next server (using next hop routing principals).
Basic call setup n n n E-mail like identifier: <sip: alice@home. com> Alice’s phone registers with home. com Bob dials alice@home. com; Phone does DNS REGISTER home. com SIP/2. 0 To: sip: alice@home. com Contact: sip: alice@m 2. home. com … Registrar office. com bob DNS lookup sip. udp. home. com Resolve to m 2. home. com alice@home. com => alice@m 2. home. com alice m 2. home. com
Basic call setup n n Phone sends INVITE; acts as User Agent Client Server can proxy the call to current location office. com INVITE sip: alice@m 2. home. com … To: sip: alice@home. com From: “Bob” <sip: bob@office. com> … INVITE sip: alice@home. com … To: sip: alice@home. com From: “Bob” <sip: bob@office. com> … c=IN IP 4 128. 59. 19. 60 m=audio 8000 RTP/AVP 0 5 8 alice m 2. home. com bob User agent client Proxy home. com
Basic call setup n n Alice’s phone rings; acts as a User Agent Server When Alice picks up, call is accepted and bob’s phone sends ACK to complete the setup SIP/2. 0 180 Ringing office. com SIP/2. 0 200 OK … c=IN IP 4 135. 180. 144. 32 m=audio 9000 RTP/AVP 0 8 alice pc 4. home. com m 2. home. com bob Proxy home. com User agent server
Basic call setup n Encoded audio packets sent over RTP office. com alice bob home. com
Basic call setup n When either party hangs up BYE is sent office. com alice BYE sip: bob@office. com bob home. com
Columbia SIP user agent (sipc) n n Media n Audio, video, text, white board n Screen sharing n Shared web browsing Advanced n Presence, instant messaging n Conference control n Emergency notification and handling n Device control
Subscribe/Notify SIP has also been extended to generate event notifications and instant messages n Users subscribe to an event with the SUBSCRIBE method and receive notifications via NOTIFY n This feature can be used for creating medical event monitoring systems n
Subscribe Request n n n Resembles that of a SIP INVITE Must have one “Event” header in the header field which will specify the type of event it is subscribing to Must also contain an “Expires” header which defines the duration of the subscription Subscriptions to multiple events requires multiple subscribe messages to be sent to the notifier To unsubscribe, it sends a SUBSCRIBE message with the ”Expires” field set to zero
Subscribe Request n Can contain optional message body in SUBSCRIBE request n Further details of notification n n methods of alerting (alarm, IM Messages, telephone calls) Filtering of sub-events Standardized grammar to automate the processing of the SUBSCRIBE request in the Notification Server If message body is not present then Subscriber will expect the default method of alert
Notify Request n n n The “Event” header will indicate the type of emergency notification it is The message body of the NOTIFY message will include specific instructions on the alert methods. Notification server receives the subscription, adds the subscriber to the particular event list and then generates NOTIFY requests accordingly
SUBSCRIBE sip: alerts@domain. com SIP/2. 0 Event: heartmonitor Expires: 86400 From: sip: alice@example. com To: sip: alerts@domain. com CLIENT (SUBSCRIBER) SIP/2. 0 202 Accepted From: sip: alice@example. com Expires: 86400 NOTIFY sip: alerts@domain. com SIP/2. 0 Event: heartmonitor To: sip: alice@example. com From: sip: alerts@domain. com SERVER (NOTIFIER)
Medical Logic Modules (MLMs) n n Medical Logic Modules (MLMs) encode medical knowledge which are used in decision-support systems. Sharing knowledge gives way to many obstacles. Typically medical institutions do not share the same decision support systems. Sharing knowledge across institutions, coordinating local vocabularies and translating the logic for automation is a strenuous process.
Arden Syntax n n n The Arden Syntax is a Medical Logic Module that has been developed for the task of sharing medical knowledge bases across many institutions. Its main focus is on knowledge used in decision support systems that can provide therapeutic suggestions and alerts. It is compiled and then run automatically to generate advice where and when it is needed.
Arden Syntax n n Contains three main sections: maintenance, library and knowledge. Maintenance section n n contains management information such as title, filename, author, etc. Library section n commenting section where the purpose of the MLM is described.
Arden Syntax n Knowledge section contains few subsections n n n type section--describes the way the MLM is to be used. data section--assigns local variables, which can be lengthy database queries evoke slot--contains the conditions under which the MLM becomes active.
Arden Syntax n n logic section--consists of the actual rule or medical condition to test for action section—describes what is to be done when the condition is true.
knowledge: type: data-driven; data: /* absolute neutrophile count */ The evoke slot anc : = read last 2 from ({query specifies that this MLM is evoked for ANC} where it occurred whenever an within the past 1 week); absolute neutrophile pt_taking_tms : = read exist count (ANC) is stored {query for TMS order}; evoke: on storage of {ANC}; logic: if pt_taking_tms /*1*/ and last anc < 1000 The logic slot says that if the patient is taking TMS and decrease of anc > 0 then and if the last ANC is less than 1000 and if the conclude true ANC is decreasing, then else execute the action slot, which sends the conclude false; appropriate message. action: store "Caution: The patient's relative granulocytopenia may be exacerbated by In the data slot, the local variable "anc" is assigned the patient's last 2 ANC's within the past week. "pt_taking_tms" is assigned true or false depending on whether the patient is taking trimethoprim and sulfamethoxazole (TMS).
Arden Syntax and SIP n Two possible ways of using Arden Syntax with SIP n n Users subscribe to Arden Syntax rules already implemented Users subscribe to Arden Syntax rules dynamically
Arden Syntax and SIP n n Users can subscribe to an Arden Syntax rule already implemented in a server. Participants within the monitoring system are aware of the Arden Syntax rules within each institution. SIP SUBSCRIBE is sent with the message body containing the name of the rule being subscribed to The server executes this rule within its system and notifies the subscriber whenever that particular rule becomes true.
Arden Syntax and SIP n n Arden Syntax rules dynamically added within a server’s knowledge base for monitoring purposes. In this example, a subscriber inserts the rule itself within the SUBSCRIBE message body. The server receives the SUBSCRIBE message and extracts the message body, compiles the syntax and then executes the logic within the syntax. The server will monitor the database and whenever the syntax becomes true, it will invoke the action specified within the rule via a SIP NOTIFY message.
Arden Syntax and SIP n Drawbacks of this method n n Since institutions each have their own custom databases, adding a dynamic syntax rule may result in incompatibility with the database that is being queried to. Unless the subscriber knows the exact query language of the remote server’s database, this will not work.
XML Messages and SIP n n XML (Extensible Markup Language) is “metalanguage”, which is a language used for describing other languages An XML schema is an XML language that defines various data types found in the XML document Popular in web-related programming Good choice for interoperability within many different types of institutional systems.
XML Messages and SIP n XML messages may be used for representing n n n n database query a filter for events subscribed to specification of alerting methods performing remote procedure calls. XQL (XML Query Language)-- general-purpose query language that is being standardized within the W 3 C Used to query a remote database assuming a common XML schema is shared XQL document is processed automatically within the notification server by interpreting the XQL document and translating it to its own database query language.
Bluetooth and SIP n n n Bluetooth is a specification that uses low-power radio signals to link phones and computers Use of Bluetooth is being considered in the medical industry Companies such as Colorado MEDtech and Code Blue Communications Inc. are developing bluetooth-enabled medical devices. These devices n provide mobile access to information and medical data acquisition. n enables devices to communicate with each other wirelessly. Bluetooth can also be used for location-based services such as detecting the doctor’s whereabouts or for establishing ubiquitous systems in the hospital environment.
5)Server calls house phone near the doctor 2)Heart monitor transmits signals wirelessly to the server 1)Doctor subscribes to server to monitor patient’s heart 3)Server process data that results in a notify being sent to the doctor’s pager Bluetooth access point 4)Doctor can’t be reached so doctor’s location is identified via his bluetoothenabled PDA and patient’s data is also transmitted to the PDA Location information sent Bluetooth access point
Benefits n Device Neutrality n n n There are likely to be range of SIP-based end systems, ranging from IP telephones, 3 G wireless handsets, IM/presence software to embedded devices. Event monitoring system can be easily extended to new devices More Information and Automated Action n n Video conferencing, text messaging Device control which causes flashing lights and aides the hearing-impaired
Conclusion n SIP is a signaling protocol that supports SUBSCRIBE/NOTIFY methods SIP-based medical event monitoring system can be implemented using MLMs or XML messages SIP provides a flexible and robust event notification architecture in conjunction with other wireless protocols
Contacts n n Knarig Arabshian (knarig@cs. columbia. edu) Dr. Henning Schulzrinne (hgs@cs. columbia. edu)
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