Illustrator, AutoCAD, & ANSYS Offer ICU Patients Mobility

By Margaret S. Gurney

The student-designed ICU MOVER includes a wheeled tower that carries important medical equipment. The devices, top to bottom,  are a cardiac monitor, an intravenous infusion pump and a portable ventilator.Images courtesy of JHU-BME

In a senior-year seminar and lab in the Biomedical Engineering (BME) Department at Johns Hopkins University (JHU), officially called BME Design Group 580.411, the task for the academic year was this: Go to the university database — described as a medical-community wish list — find a need that has not been met and develop a design to solve it. Simple as that.

“The course was called Design Team, colloquially, among the students,” says Ravy Vajravelu, a senior during the project who collaborated with his roommate and three other students to form the team (four seniors and one sophomore) that tackled the task.

  The JHU database is huge, explains Joshua Lerman,  Vajravelu’s roommate and team leader. It collects local submissions from physicians and nurses in the Baltimore area into a working database developed by the JHU BME department. Lerman recognized that many of the needs catalogued could not be met in a single year, and his team needed to locate an item and create a product that could be put to use by a real patient by the year’s end.

Project Selected
Lerman and Vajravelu — colleagues currently pursuing advanced degrees — soon found just what they were looking for. They came across an entry from Dr. Dale Needham, Assistant Professor in the Division of Pulmonary & Critical Care Medicine, and Department of Physical Medicine & Rehabilitation at Johns Hopkins University, who was conducting a quality improvement (QI) project focused on increasing physical activity and ambulation for intensive care unit (ICU) patients. These patients typically require use of various monitoring and life-support devices; hence, ambulating one ICU patient often requires simultaneous involvement of four ICU caregivers. It was surmised that design of a novel biomedical device could free up two caregivers, thereby making ambulation of ICU patients more feasible. The project’s full name: The Mobilize Our patients for Very Early Rehabilitation (MOVER) Aid for Intensive Care.

  The project was seeking a walker that would enable ICU patients to stroll the hallways with life-support accoutrements in tow; this device would have to include a rugged seat that could catch a fall should the patient lose balance. Secondly, they needed a wheeled tower on which to mount the monitoring and life-support equipment.    Together the walker and tower needed to be narrow enough for use within the ICU hallways. To use Needham’s own words: “In general terms, we envision a device which incorporates a four-wheeled walker with armrests and a seat,  manifolds for a portable ventilator and monitoring equipment, a suspension pole for intravenous fluids, and a receptacle for an oxygen tank.” 

For the students, such a project was noninvasive, presented no toxicity threats, and would be inexpensive to accomplish. It also promised a time-to-market period of about one school year.

  Vajravelu explains that he drew all of the preliminary conceptual designs by hand, often on a white board. These drawings were based on team discussions of the design needs in order to be both suitable and possible within a tight budget.

Once the digital model was completed, it was time to create a preliminary prototype, shown hereusing PVC and other readily available materials. Photo by Will Kirk

When they came to actual dimensions, the biomedical engineering students started with graph paper. Yet Vajravelu admits that because his art skills were not up to par, he turned to Adobe Illustrator in short order — in order to capture the team’s preliminary concepts. He also knew that the solution would come in handy down the road when the team would need a solid model, to plan for and determine the costs of materials, and to present their proposal to win funding.

  Lerman explains that Illustrator was critical to be able to properly present the concept to others. “To sell the idea, it helps to have a flashy presentation, for investors and judges to understand better, as well as helping with funding — and also with grades.” The team understood that the better it could present the project, the more seriously it would be taken, and the closer they could come to making a prototype fly. “People don’t want to hear your ideas, they want to see your ideas,” Lerman says.

“I used Adobe Illustrator and even Photoshop to begin with because I needed ]representations] to be attractive to show the walker and the material,” says Vajravelu. “I used Illustrator to touchup the hand-drawn sketches in order to present, plus the unit would need to be drawn to scale before it could be built, basically to understand how the pieces would fit together. And this presented a problem, as they had to see if the pieces would fit on the design once built.”

  Although none of the team members knew CAD, they knew they needed a program to keep the design true to its original intention.

AutoCA D models in different stages of development;  on the left is midway and the final is on the right. Note the improvements. Imagescourtesy of JHU-BME

Enter the Freshmen
As biomedical engineering students, not mechanical engineers, the team needed to recruit some help. At the start of the project’s second semester, the team found a couple of freshmen who had some design experience and were able to both run with the project, and gain increased proficiency in CAD along the way.

“The design was pretty much finished before we got it into AutoCAD,” says Vajravelu. “We had the final design in Illustrator and actual mockups, but by second semester we found a student who was experienced in AutoCAD who took the final design and put it into AutoCAD. We needed to give the manufacturing side information on how to build the device.” Once a digital model had been created, it was used to fine-tune the preliminary prototype.

  The team picked AutoCAD software because, as Lerman explains, the learning curve was easy. Soon, he says, the freshmen had exceeded his expectations and the working CAD model of the physical prototype was taking shape. Testing, adjustments, materials, and more adjustments were now all as simple as changing a few dimensions here and there on the digital model.

Seat Design & Materials Selection
Lerman explains that the upperclassmen used ANSYS to calculate the walker’s center of gravity. They put up their basic sketches to test for tipping: how much force (how many pounds of force) is required to tip the unit in any direction? They entered the maximum values for the center of gravity — just the basic sketch was needed in order to perform the calculations, not the full design.

“After we had the center of gravity we tried to see how much force was required to tip the device in most directions (forward, backward,  sideways). Then the freshman came along and showed us a button in AutoCAD to locate the center of gravity!” says Lerman.

  Second, a materials search was under way for the seat — one that could handle a maximum weight limit of 250 lbs., and could be easily cleaned. So they migrated the design from Illustrator into AutoCAD, finding that the more detailed the sketch in AutoCAD the less they had to redesign from scratch.

“When we needed a stronger material, we changed the properties in the program and designed it for a stronger center of mass,” says Lerman. “We needed to see how the change in material would affect the mass in terms of stability of the unit…we did not want it to tip over when someone sat down in it.” They had to determine if the seat was placed in the correct area of the unit, and they needed to be certain the material in the seat was strong enough to break a fall.

“In the end,” Vajravelu said, “we had a CAD model built out of PVC, and it looked good. Several cheap prototypes and mockups went back and forth, and due to AutoCAD, the PVC went back in CAD; it was reverse-engineered,  so we could see it in CAD, and then make more changes — in CAD. CAD allowed us to explore — laser scanning was out of the question, as we had no funding for laser scanning.”

“It was awesome to see — it was built exactly as it was designed,” says Lerman.

Joshua Lerman of Delray Beach, Fla., leader of the Johns Hopkins biomedical engineering student team that designed the ICU MOVER, tests its safety seat, surrounded by other members of histeam, including his colleague Ravy Vajravelu, fourth from left. Photo by Will Kirk

The Rest of the Story
When asked whether the unit would be commercially developed,  Vajravelu said they hope a company will eventually pick it up. He said they have patents pending. But Vajravelu never lost sight of his ultimate goal, to get patients healthy again. “It was an outside shot,” Vajravelu explains, “to give the ICU something that clinicians could actually use — to see how engineering works in the real world — it’s unusual for a project to get to actual patient use…so quickly.“

  According to JHU, the prototype has been used in the medical ICU at Johns Hopkins Hospital.

  Joshua Lerman graduated from Johns Hopkins University with a B.S. in biomedical engineering in May 2008 and is pursuing his Ph.D. at UC San Diego in bioinformatics and systems biology, a program that will take five years. His colleague, Ravy Vajravelu, who graduated with a B.S. in biomedical engineering as well, recently started medical school and has plans to participate in medical device development.

  Vajravelu explains that this project was successful because the team “chose the right project — this was a noninvasive therapy aid, a rehabilitation device requested by a physician-scientist who needed to understand if, and how, mobility and rehabilitation for ICU patients could improve their health outcomes. This project was to help him with his project. Ultimately, he is the one who is in the process of discerning if physical movement helps in recovery.”

  Dr. Dale Needham has promoted the device at a small international medical conference in Canada and has talked to several interested physicians about it. He adds that “The QI project is progressing quite well —  it is a huge success.”

More Info:
Adobe
San Jose, CA

ANSYS
Southpointe, PA

Autodesk, Inc.
San Rafael, CA

Johns Hopkins University
Div. of Pulmonary &  Critical Care Medicine
Baltimore, MD

Margaret S. Gurney is the editor for new products at Desktop Engineering magazine. To remark on this article, send your comments via e-mail to [email protected].