Recent events have unfortunately reconfirmed the simple truism that war is hell. But the grim business of having to place U.S. troops in harm's way in the Balkans serves to highlight engineering projects to allow surgery in front-line battle areas that could dramatically improve wounded soldiers' chances for survival.
The major enemy combat medics face in battle is time. Resuscitative care received within the "golden hour" 60 minutes after injury improves survival significantly. But despite the availability of helicopter evacuation from combat zones, U.S. military surgeons and planners realize that treatment as close to the battlefield as possible would best boost the chances of wounded personnel.
Enter ASSTC. To bring effective, timely care to the battle lines, the military is literally putting a hospital in a box--the Advanced Surgical Suite for Trauma Casualties (ASSTC). A 5 x 5 x 10-ft package, ASSTC weighs in at 3,600 lb (including 1,000 lb of medical supplies), can be set up in 16 minutes, and allows 20 medical procedures in 24 hours. The box's carbon-composite and aluminum walls fold down to form the floor of the single-bed surgical suite. A patent-applied-for sealed hinge design maintains sterile integrity and keeps out water in both open and closed positions--critical if the hospital-in-a-box is stored for months on the deck of a ship.
This technology is the result of work started by the U.S. Army Medical Research and Material Command (USAMRMC, Ft. Detrick, MD) which had been looking at how best to move life-saving surgery, such as clamping arteries and patient stabilization, closer to the battle or provide timely helicopter evacuation. For the latter, the Army Medical Development Center (Ft. Sam Houston, TX) was advocating the Q Helicopter with precise GPS navigation to transfer casualties to more complete medical facilities behind the battle lines. But even these $38 million machines have no means of treating a patient during the precious transfer minutes.
|The hospital-in-a-box ASSTC has a positive-pressure surgical suite and recovery area to offset the effects of chemical and biological agents. Life Support for Trauma and Transport (LSTAT) carriers, with self-contained ventilators and other equipment, stabilize patients before and after surgery and allow their transport.|
Col. William Weismann, former USAMRMC director, found funds from the Marine Corps Combat Development Command (Quantico, VA), which allowed a joint-service development effort along with swift issuing of system requirements by the Marine operation.
Early in 1997, military and civilian trauma surgeons addressed the best way of reducing combat fatalities, and took a hard look at the need for front-line (or full-forward) surgery. These specialists concluded that the number one need was more effective hemostasis--stopping bleeding. Next on the list was a "bandage" that could seal off a severed limb (see p. 90), followed by the ability to do procedures in a relatively controlled, clean atmosphere.
Quick reaction. The USAMRMC also enlisted the aid of engineering students at Harvey Mudd College (Claremont, CA). The students brainstormed a forward-field medical facility. Then, engineers at the Oak Ridge Centers for Mfg. Technology (ORCMT, Tennessee) developed a digital model for it. ORCMT combines the capability of the Department of Energy's Oak Ridge National Laboratory and its Y-12 Defense Production Plant. It is run by Lockheed Martin Energy Systems and noted for its broad technology base and experience in rapidly producing all kinds of systems. The services, now including the Air Force, then gave the go-ahead for prototype construction with a deadline only 10 months since concept digitization.
|Historically, 90% of combat deaths occur on the battlefield, with the remainder occurring after the patient reaches a treatment facility. Two-thirds of the fatalities are due to blood loss and critical injuries. Its developers estimate ASSTC use will result in 20 to 25% fewer deaths. (Data from the Defense Technical Information Center.)|
Key constraints placed on the designers were:
Store the system within a 5 x 5 x 10-ft box (in order to fit inside a Marine MV-22 tilt-rotor aircraft) and open to a 30 x 30 x 10-ft facility
Weigh less than 4,000 lb (the maximum tongue load for a Humvee)
Setup and knock-down within 30 minutes by a crew of 10
Quick "plug-and-play" mission reconfiguration
Watertight transport and deployment, and resist chemical and biological agents.
Deployed with Marines aboard ship, the ASSTC will be fitted with supplies for resuscitative surgery. "But by dropping a panel, individual drawers in the cabinets can be changed to allow for other types of surgery or humanitarian aid such as health maintenance and disease prevention," says G. Wayne Morrison, ORCMT medical technology program manager. "The medical supply drawers on the latest Marine transport ships are compatible and interchangeable with those in the ASSTC."
Equipment within the ASSTC can include digital x-ray and anesthesia machines, blood serum and plasma laboratory, oxygen generator, blood refrigerator, resuscitation fluid warmer, and a computer and communications station to relay patient data and arrange follow-on treatment. The unit is compatible with the Life Support for Trauma and Transport (LSTAT) "emergency room on a stretcher" and wirelessly communicates with LSTAT patient sensors (Design News, 11/16/98, p. 41).
The single-patient surgical suite ASSTC core is surrounded by a triage and recovery area, all of which are enclosed in a tent shelter. Pressurization keeps out chemical and biological warfare agents, as does the outer tent layer. Cabinets in the core area walls are accessible from both the suite and recovery areas. Within ASSTC, a self-contained air-handling system from Ebac (Williamsburg, VA) regulates the pressurization and HVAC system. Standard military field electrical generators supply power. ASSTC requires 15 kW; 75% of this power goes to the air-handling functions and the rest to lighting, medical, and communications equipment.
In popping a compact medical facility out of a tightly packed box, a key design consideration was ergonomics. Steve Litherland, ORCMT technical engineer for ASSTC, notes, "While the design is not rocket science, just a box that folds out, it was an exercise in packaging and keeping things light." To this end, IGRIP design software by Deneb Robotics (Troy, MI) let engineers conceptualize the design so that doctors could "walk through" the facility to see how well they could function in it before any metal (or composite) was cut. The package also produced animations for report presentations.
ORCMT brought Duvall Designs (Rockport, ME), specialists in architectural fabric structures, onboard the team to design the tent-like covering. Vice President Patricia McDonald says designers first put the basic idea on paper. Then a PC- and Mac-level modeling design program, form- Z by auto- des- sys (Columbus, OH), allowed the small firm to produce the final digital design drawings.
The canopy consists of three layers. The inner tent is a double layer of breathable nylon rip stop. This inner portion is connected by a baffle system to an outer layer of urethane-coated nylon. Separation between the layers is 3 inches for thermal insulation. Over this is an outer rain fly, looking much like a camping tent but similar to a metallized plastic "space blanket" with laminated plastic wrap for biochemical resistance.
Rural route. The day after the ASSTC prototype was handed to the services, it was trucked to Hancock County in northeast Tennessee. In this rural area so strapped for funds that it cannot support a single doctor, ASSTC was used to take x-rays and provide flu shots and infant inoculations--an immediate demonstration of civilian medical applications for ongoing care and disaster relief potential. Now, according to ORCMT's Morrison, the Federal Emergency Management Agency (FEMA) is considering stockpiling ASSTCs around the country, at least one per state, for disaster aid.
The Marines have evaluated the ASSTC for a year in field trials at Camp Lejune, and last October used it in a live fire exercise in Turkey. This past April, live pig trials of the entire concept were scheduled for a more dramatic evaluation. While grim in concept, such work may save soldiers in the future. In these tests, fatal wounds are inflicted on the animals. They are then brought into the ASSTC where surgeons do life-saving procedures and stabilize them. The pigs are then flown in a helicopter to simulate combat evacuation to a rear facility, where definitive surgery is performed.
The Marines may be ordering 30 ASSTCs for delivery in fiscal year 2001. The Army--which is not under the Marines' size requirement for MV-22 transport--may develop a two-bed operating suite version in a box 15 ft long.
Finally, how important will such medical mobility be in future wars? As an example, during the Gulf War ground offensive, a 20-bed Marine Corps Surgical Support Company needed to move to keep up with advancing units. After numerous truck sorties over five days, the unit was not fully moved and the war was over--what should have been medical support became a logistics logjam under mobile warfare conditions. The classic Mobile Army Surgical Hospital (MASH) facility was not mobile enough. ASSTC will bring traumatic care directly to future combatants more effectively--and bring more soldiers back out of harm's away.
Dual-use structural components
Replaceable-module systems design
Design and analysis software
Co-located, integrated design team
Rapid prototyping expertise
Broad manufacturing capability
Size envelope and weight limit
Fast set-up and knock-down times
Quick mission reconfiguration
Watertight during storage and deployment
Resistance to chemical and biological agents