DN Staff

March 3, 1997

5 Min Read
Portable trauma unit may save more soldiers

Pico Rivera, CA--Soldiers of the future may have a better chance of surviving serious injuries thanks to LSTAT, the Life Support for Trauma And Transport. Looking like a space-age stretcher, first generation LSTATs contain an on-board ventilator, defibrillator, suction unit, IV infusion pump, blood-chemistry analyzer, oxygen bottle, and advanced patient monitoring and data logging systems. Future versions should include a sophisticated environmental control system, as well as an advanced oxygen generator.

Its role is to address what the medical community refers to as the "golden hour," the first 60 minutes after an injury when most fatalities occur. "Since the civil war, very little has been done to improve survivability on the battlefield," says Todd Kneale, LSTAT advanced projects manager at Northrop Grumman's Advanced Technology and Development Center (ATDC). While medical hospitals have advanced enormously since Appomattox, the majority of the injured who die do so during the trip from the battlefront to the field hospital. The solution? Bring some of the hospital to the patient.

"LSTAT projects care as close to the injury as possible," Kneale explains. It can be used for transportation or resuscitation at the site of injury, in-theatre for surgical stabilization, or as an operating table. A range of physiological sensors can gather data to aid treatment and to assist later research. And communications systems can provide patient status to medics or transmit the information to doctors outside the arena.

Rather than reinvent numerous portable medical components, engineers designed LSTAT to integrate previously approved, state-of-the art, commercial standalone devices. "We were looking at the shortest route to put this into operational use with the military," says Richard Raiford, manager of ATDC's new product development. "So we used FDA-approved devices." While it may be the short route, this approach posed massive system-integration challenges that included:

Keeping LSTAT's overall weight under 100 lbs.

  • Developing physical interfaces that would mate with numerous transport vehicles.

  • Allowing the use of electrical power supplied by ground vehicles, aircraft, or wall current almost anywhere worldwide.

  • Creating an integrated data retrieval, storage, and display system.

  • Ruggedizing the complete package from physical abuse as well as EMI interference.

"It wasn't just an issue of getting all the pieces in the box, you had to deal with noise, interference, vibration, balance, and maintenance issues," says Kneale.

His team leveraged Northrop Grumman's composites experience to create LSTAT's shell, called the sled. For the proof-of-concept articles, they experimented with a vacuum assisted resin transfer molding (VARTM) method that offers the potential for high volume and low cost. Graphite materials in a vinyl-ester resin matrix comprise most of the structure, with both glass and KevlarTM layers as appropriate. But for the first six prototypes--due to be finished in early 1997--they selected a hand layup. The prototypes weight about 135 lbs, but that is expected to drop to near 100 lbs in production.

The need to interface with the Blackhawk and Huey helicopters, Humvee ground ambulance, and Air Force long-haul aircraft dictated the sled's un-usual envelope. LSTAT also has to accept the standard NATO litter, and does so with four latches--one on each end of the two litter poles--that capture the poles automatically.

A data-logging capability stores up to 24 hours of device settings and patient data--gathered from the physiological sensors--to two miniature, ruggedized disk drives. A similarly EMI- and shock-hardened CPU provides real-time signal-processing power. Both medical and system components are arranged to meet the conflicting drivers of weight and balance, ergonomics, and EMI protection. "We have a great deal of experience with EMI from designing stealth aircraft," says Kneale. This background let them create shielding that didn't weigh too much, but protected the sensors and medical devices from extremely "dirty" environments, as in a helicopter.

Display concepts are still being developed. The goal--demonstrated in proof-of-concept articles--is a pivoting touch screen that can be changed with a few commands from a simple, prompt-driven interface for field medics to a highly detailed control system and waveform display for doctors. For now, LSTAT makes use of the displays that are part of the commercial patient-monitoring systems integrated into the system.

Linked to LSTAT through a tethered Ethernet connection, a hand-held secondary display works as a nurse's station to monitor the patient's condition. It can be used, for instance, when the primary controls are blocked during vehicle transport. Ultimately, engineers intend to make this link wireless and allow attendants to monitor multiple LSTATs from one station.

A common power bus accepts 28V ground power, 400 Hz aircraft power, and both U.S. and European wall current. Onboard batteries will drive the unit for 30 minutes or more, depending on the number of devices used.

Engineers relied heavily on several CAD programs to take LSTAT from idea to concept model in nine months and then on to prototypes and FDA submittal less than a year later. One of the most useful was Parametric Technology's Pro/ENGINEER(R) running on Silicon Graphics Indigo workstations. "Timelines were significantly reduced through the use of Pro/ENGINEER," says Kneale. "We were able to almost eliminate manufacturing rework, even at this prototype stage."

The project is directed by the Walter Reed Army Institute of Research and sponsored by the Defense Research Projects Agency. It's a "live" program espousing a flexible architecture that will continue to evolve as new sensing, processing, and display technologies are developed.

Someday, LSTAT may even take a more active role. Says Kneale, "We're moving towards an onboard mentoring capability, where the system will evaluate patient status and then give recommendations to medics about patient care."

Additional details...Contact Northrop Grumman Corp., Public Information, 1840 Century Park East, Los Angeles, CA 90067-2199, (310) 553-6262.

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