Public Safety Net
- By Brian Robinson
- Apr 04, 1999
Being involved in a traffic accident is nobody's idea of fun, but if it has to happen, your best chances may be in San Antonio. That's because the Texas city is home to a bleeding-edge marriage of communications and public safety technologies that could make it one of the world's most advanced centers for trauma care.
Through a project called LifeLink, the city is experimenting with a combination of wireless and fiber-optic links to give emergency room doctors at a hospital a look at a patient in an Emergency Medical Services (EMS) ambulance.
The ER team previously was dependent on a paramedic to describe a patient's condition and symptoms en route to the hospital, but LifeLink gives doctors the opportunity to see the patient for themselves and get simultaneous readouts of vital statistical data.
LifeLink, which began operating in October, is part of TransGuide, a partnership among the city of San Antonio, the metropolitan transit authority, the Texas Department of Transportation (TxDOT) and several San Antonio research organizations. Begun in 1993 and formally opened in July 1995, TransGuide was selected a year later as one of four sites for the federal DOT's Intelligent Transportation Systems (ITS) Model Deployment Initiative (MDI). Seattle, Phoenix and New York are the other sites.
The goal of TransGuide, as with other ITS programs across the country, is to use advanced technology to better manage traffic flow and to provide better response to accidents and other emergencies. LifeLink, however, seems to be far beyond what any other area is trying in terms of providing EMS.
"We have actually been interested [in ITS] since the early 1980s, but the twisted-pair wire technology available to us at that time just wasn't capable of handling the kinds of communications we wanted," said Pat Irwin, director of transportation operations for TxDOT's San Antonio division.
Fiber optics and digital communications technologies eventually were developed to the point where TxDOT felt it could commit to the project. Those technologies allowed for a great deal of expansion in TransGuide capabilities, Irwin said. With a lot of prodding from the medical community, it was agreed that if TransGuide allowed ambulances to communicate with emergency rooms, the partnership would look seriously at putting such a program in place.
The proposal for what would become LifeLink was put forward by the SouthWest Research Institute (SWRI), a nonprofit organization that does about $300 million a year in contract technology research for clients. SWRI funded a proof-of-concept program internally, and the project was carried forward with TxDOT funding.
At a cost of about $20,000 each, 10 fire department ambulances-out of a fleet of 24-are outfitted with ruggedized computers, video cameras and microphones. That setup allows for two-way video sessions between the ambulance and the hospital. Transmission of patient statistical data from portable medical instruments is enabled with on-board 2.4 GHz computer-controlled wireless spread-spectrum radios.
These radios communicate en route to the hospital via a system of 59 receiving antennas placed at TransGuide fiber hubs alongside the freeway. The communications are sent from the hubs over fiber-optic lines to the TransGuide Operations Center. From there, the transmissions are carried via a T-1 phone line to the hospital. The reverse path handles hospital-to-ambulance communications.
"It's line-of-sight wireless technology," said Sterling Kinkler, principal engineer with SWRI. "As long as you can maintain that line of sight, then the system can be used in any conditions, rain or shine, night or day."
The system on the ambulance acts as a node in a mobile local-area network, Kinkler explained. LifeLink, for the most part, uses standard Ethernet protocols that in turn enable system managers to use Simple Network Management Protocol to configure the switching equipment that's used as well as the computers that control the spread-spectrum radios.
When LifeLink is in use, a paramedic in an ambulance and a doctor at the hospital wear headphones with a microphone to communicate with each other. Each can view video screens showing both the image being received on the full screen and the image being sent in a smaller window.
The physician's screen in the emergency room will show a picture of the injured victim, and the physician can tell the paramedic in the ambulance to move the video camera over the area of the patient's body he wants to focus upon. The paramedic uses a remote control device to move the camera and to zoom in and out on an area. The physician could control the camera from his console in the ER, but for now the paramedic has control over what happens in the ambulance.
Vital patient data is collected with the on-board computer and is combined with the video signal so that it be can assessed at the same time the physician is visually evaluating the situation.
In the ambulance, the paramedics' screen shows the hospital physician, and a smaller frame shows the video images being sent to the ER doctor. The screen, however, is out of the patient's line of sight. The ambulances also are outfitted with open-ended microphones that the paramedic can turn on if the doctor wants to ask the patient questions.
The on-board system was designed to be as simple to use and maintain as possible, Kinkler said. It's basically a one-button operation for the paramedic because his or her responsibility is to the trauma victim and not to operating the LifeLink equipment. In addition, the system is built in a modular fashion so that if one of the components fails, it can be pulled out and replaced rather than repairs having to be made aboard the ambulance.
Also, if the video signal breaks up for any reason, a failsafe ensures that the ER doctor will be left with the last good digital frame received on the hospital video screen until communications are restored. Even if communications are breaking up, Kinkler said, the patient's vital data often can get through.
Given the newness of the system and the usual resistance to change on the part of professionals who have long-established ways of doing things, the use of LifeLink has been tentative.
"We are certainly not using it yet on a daily basis," said Alex Mcleod, an EMS captain with the San Antonio fire department. "But most EMS people seem to like the system, and the potential is certainly there to use it more often.
"So far it's been used in the more serious cases we attend, but now we might kick it up a notch and use it more often if we feel we need more of the physician's input, such as when someone is in full cardiac arrest and we have to do many invasive procedures," Mcleod said.
Charles Davis, an ER physician at University Hospital, said the system has been used only marginally by ER doctors so far, but its potential is obvious. Only increased use and a much longer period for evaluation will tell how useful LifeLink will be, and one of the most important opinions will be that of the EMS community. "They have to find it useful for what they do," Davis said.
If that's the case, LifeLink may be a shoo-in for a much longer life.
"It's such a natural fit for us," Mcleod said. "After all, that's our job in any accident: to function as the physician's eyes, ears and hands."
Brian Robinson is a free-lance journalist based in Portland, Ore. He can be reached at firstname.lastname@example.org.
TransGuide and LifeLink Safety Specs
The TransGuide Intelligent Transportation Systems (ITS) project uses in-road and other sensors together with remote-controlled video cameras to analyze and control traffic flow on the San Antonio Freeway. Some 26 miles of the freeway have been outfitted and are operational, with another 28 miles due to come online within the next couple of months. Eventually, about 200 miles of freeway and city streets should be a part of TransGuide.
For the operation of LifeLink, 2.4 GHz spread-spectrum radios on board EMS ambulances transmit video, voice and data information, acting essentially as IEEE 802.11 Ethernet bridges to connect the ambulances with roadside TransGuide fiber hub subsystems.
Transceivers at the hubs convert the 4 megabits/sec data stream from the radios into full 10 megabits/sec streams that are fed through a dedicated wave division multiplexed channel in a fiber-optic cable running from the hub to the TransGuide Operations Center. This data then is fed to the trauma center at the hospital, initially by a leased T-1 line but eventually through a dedicated fiber-optic link.
A ruggedized PC in the ambulance and a compatible PC operating at the emergency room provide videoconferencing sessions between paramedic and physician through codecs that support H.261 video capture, compression and playback. Video capture is at the common intermediate format resolution of 352 by 240 pixels, 15 frames per second and a data rate of 512 kilobits/sec. Patient data, collected from monitoring equipment on board the ambulance, is sent along with the video through a separate data channel that operates as a 38.4 kilobits/sec RS-232 link.
A videoconferencing session can be initiated only by the paramedic in the ambulance. The hospital is designated as the control node during the communications, and the ambulance can talk with only one control node at a time. The initial control node hospital can hand control over to another hospital if required, or it can include other hospital nodes into the session as "consultant" nodes.
- Brian Robinson