Technical Report AMI-005:

Review of 2005-2006 RERC-AMI National Student Design Competition: Patient Positioning Aid

Authors: Erin Promersberger, B.S.

Coordinating Editor: Melissa Lemke, M.S.

Location: Medical Device Accessibility & Usability Laboratory, Marquette University

Current Version: 1.0 (August 2006)

Table of Contents

Executive Summary

The Rehabilitation Engineering Research Center on Accessible Medical Instrumentation (RERC-AMI) has sponsored the national Student Design Competition for the past three years. As part of the 2005-2006 competition, eight teams designed patient positioning aids for 6 fictional clients with various disabilities. It was specified that the prototype be versatile, low-cost, easy to store, easy-to-adjust by a medical professional with limited strength or flexability, work with a range of examination tables and imaging systems, support the segment weight of a 500 pound person, and support a variety of body segments and positions.

Background

Imaging is important in the diagnosis and treatment of medical conditions because it is cost-effective, noninvasive, and can determine the precise location and severity of diseases such as cancer, Alzheimer's disease, Parkinson's disease, stroke, and heart failure. The most commonly used techniques are X-ray, computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound [1]. Due to aging of the population, imaging expenditures are expected to increase to $2.3 trillion, 17% of the gross national product, by 2007 [2].

Unfortunately, patients with disabilities often struggle with transferring and/or holding a specific position for an extended period of time, which may result in an incorrect image, diagnosis and/or treatment plan. According to the 2002 United States Census, 18.1% of the total population, and 52.3% of people over the age of 65 have a disability [3]. Between 1962 and 2000, the percentage of obese Americans increased from 13% to 31%. Currently, 62% of the population is overweight, with a body mass index greater than 25.0 [4]. In addition, nursing is one of the riskiest professions due to the intense physical demands of transfers [5]. Due to the prevalence of persons with disabilities and the high risk of back injuries among nurses, it is necessary to improve the process of transferring patients.

Static positioning is also an issue, especially among persons with limited motor control. The most common positioning aids used today include foam wedges (Figure 1), wrap-around coils (Figure 2), pillows, handles, braces, vacuum pads, and acrylic knee supports. Many of these aids are ineffective because they only satisfy the needs of specific patients. In addition, it is difficult to obtain accurate and repeatable rotation if a specific position is desired.

This figure shows eight different foam wedges which could be used for a variety of applications.

Figure 1. Foam Wedges [6]

This figure shows a wrap-around coil at two different positions on the leg.

Figure 2. Wrap-around Coils [7]

During the 2005-2006 academic year, eight engineering design teams from across the country designed patient positioning aids for the National Student Design Competition. This competition was sponsored by the Rehabilitation Engineering Research Center on Accessible Medical Instrumentation (RERC-AMI), and the overall competition included 22 teams from 16 universities competing in three categories (see: http://rerc-ami.org/ami/projects/d/2/2/year3/). The specific aims, specifications, and clients (see Table 1 below) for the patient positioning aid are shown below [8]:

Aim: A versatile, low-cost, easy-to-adjust patient positioning aid that works with a range of examination tables and imaging platforms and meets the needs of the clients below.

Specs: The positioning aid must support the segment weight of a large person (up to 500 pounds total body weight), be easy to adjust for transferring or position maintenance even for medical professionals who have limited strength or flexibility, easy to store, compatible with different imaging technologies and table types (e.g., CT, MRI, x-ray), and able to support a variety of body segments and positions.

Clients: Joan, Lloyd, Sophia, Arnold, Dave, Bruce

Table 1. Patient Positioning Aid Personas

Client Brief Description
Joan Heart Failure, Sedentary, Fragile, Weak
Lloyd Diabetes, Poor Eyesight, Hearing Loss, Overweight
Sophia Limited Right Arm Function, Requires Cane
Arnold Diabetes, Parkinson’s Disease, Tremors
Dave Limited Use of Right Arm and Leg, Sometimes Uses Cane
Bruce Paralyzed Legs, Uses Manual Wheelchair, Renal Failure

See http://rerc-ami.org/ami/projects/d/2/2/year3/ for a complete description of these personas and rules for the 2005-2006 competition. The maximum budget for each project was $2,000.

Product Table

The Product Table compares seven of the designs entered in the design competition (one of the web sites expired before this evaluation). Although all teams followed the same problem statement, some focused on the transferring issue while others focused on the positioning issue.

The first two rows give the name and manufacturer of the device. Next are cost, length, width, and height of the design. In the case of multiple devices (such as Marquette's Accusupport), the dimensions for each are listed, separated by a comma. The weight limit lists the weight that can be supported by each device based on testing or analysis.

The next fifteen rows list criteria including: support segment weight of 500-lb person, support a variety of body segments, support a variety of positions, prone position, supine position, arm above head, sitting position, side-lying position, standing position, works with a range of table types, works with a range of imaging platforms, easy-to-adjust for transferring, easy-to-adjust for position maintenance, easy to store, and cleanable. Each is ranked on a scale of 1-3: a "3" signifies that the device completely satisfies the criterion, and a "1" signifies that the device does not satisfy the criterion. The next two rows, reusable and padding/comfort, use a simple yes/no to determine whether the device met the criteria.

The last row evaluates user abilities. Persons with the impairments listed should not have problems operating the device. For a list of impairment abbreviations, see the note at the end of the Product Table.

Survey of Prototypes

Marquette University designed AccuSupport: a combination of 4 different supports (arm, leg, head, and versatile) that are compatible with imaging systems. Polystyrene provides the structure for the arm and leg supports, while the head support is made of a combination of stiff foam and polystyrene cushioning. The universal support, which can be used under the back, ankles, or feet, is composed of a Plexiglas base, polystyrene beads, and a stretch vinyl covering. The leg support is shown in Figure 3 [9].

This figure shows the leg support (in use) designed by Marquette University.

Figure 3. Leg Support designed by Marquette University

Team 1 from St. Louis designed the Rotoflex head and neck positioning system, shown in Figure 4. This device uses two cylindrical sections of high-density polyethylene (HDPE) construction pipe, with ball bearings between them to minimize friction. This device allows for accurate and repeatable rotation, flexion, and extension [10].

This figure shows the Rotoflex head and neck positioning system (in use) designed by St. Louis University, Team 1.

Figure 4. Rotoflex head and neck positioning systems designed by St. Louis University, Team 1

Team 2 from St. Louis designed two positioning supports: an arm stabilizer (Figure 5) and a leg stabilizer (Figure 6). Materials include a polyvinylchloride box, two polyethlene bladders to hold the limb in position (one positioned on each side of the limb), a gear to allow for precise rotation, a polyethylene screw to hold the gear in place, a shelf that supports the limb, and a Velcro strap to secure the limb to the shelf [11].

This figures shows the arm stabilizer (in use) designed by St. Louis University, Team 2.

Figure 5. Arm stabilizer designed by St. Louis University, Team 2

This figure shows the leg stabilizer (in use) designed by St. Louis University, Team 2.

Figure 6. Leg stabilizer designed by St. Louis University, Team 2

Stony Brook University designed supports, shown in Figure 7, which consist of laminar foam, polyurethane encapsulation, air valves, and a covering. Air valves allow these supports to conform to a specific patient, maintain their shape for an extended period of time, and return to their original shape for the next patient [12].

This figure shows two supports designed by Stony Brook University.

Figure 7. Supports designed by Stony Brook University

Connecticut designed a patient transfer board. It has a polyethylene frame and is hinged for easy storage. The foam aids in patient comfort and positioning. Clamps are used to hold the patient's arms in position, and other positioning devices (arm grips, arm boards, leg boards, knee crutches) can be attached to the board. Figure 8 below shows the patient transfer board [13].

This figure shows the transfer board designed by University of Connecticut.

Figure 8. Transfer board designed by University of Connecticut

The University of Wisconsin at Madison designed the Roller PATH: a device with an imaging bed track and a hospital bed track. Figure 9 shows the device on a flat surface and Figure 10 shows the device on an imaging track. Columns of wheels assist with transferring a patient from one track to the next. This device is designed such that static positioning aids currently on the market, such as foam wedges, can be used with it [14].

This figure shows the Roller PATH designed by University of Wisconsin-Madison.

Figure 9. Roller PATH designed by University of Wisconsin-Madison

This figure shows the Roller PATH (in use) designed by University of Wisconsin-Madison.

Figure 10. Roller PATH designed by University of Wisconsin-Madison

The team from Catholic University designed the Patient Imaging Transfer System (PITS). The idea behind this system is that it can act both as a wheelchair and a gurney. The prototype contained three components: bed, base, and transfer system, as shown in Figure 11 below. The base can be elevated to the height of the imaging table and the chair reclines, allowing the patient to transfer to the imaging table from the side. The computer model of this configuration is shown in Figure 12 [15].

This figure shows the wheelchair/gurney prototype, in wheelchair form, designed by Catholic University.

Figure 11. Gurney/wheelchair designed by Catholic University

This figure shows a drawing of the wheelchair/gurney, in gurney form, designed by Catholic University.

Figure 12. Gurney/wheelchair designed by Catholic University

Unfortunately the University of Minnesota website expired before this report was written, therefore no details are provided for this design.

Evaluation of Prototypes

In June 2006 a group of four judges evaluated each design and awards were given to the highest-scoring designs. Marquette won first place in the competition with AccuSupport. Observed strengths of this design are its radiolucent materials and versatility in body segments and positions. The Connecticut and Madison teams tied for second place. Connecticut's transfer board is unique in that it addresses both transfer and static positioning. Other strengths include radiolucent materials and easy storage. The main strengths of Madison's Roller PATH are radiolucent materials and fewer patient transfers required. The Catholic University team won third place with the Patient Imaging Transfer System. Strengths of this device are fewer patient transfers and less work for the provider.

Recommendations

Addressing all aspects of the problem statement turned out to be challenging for each of the teams, and overall no device completely satisfied the requirements of the problem. However, each design prototype brings unique strengths that could be combined to form one product. One idea is to use Catholic's wheelchair/gurney idea with Madison's Roller PATH. Both ideas minimize patient transfers required, Catholic's design minimizes work required by the health care provider, and Madison's design can be used with various imaging platforms. Some features from Connecticut's design, such as the arm clamps and attachments for other positioning devices could be incorporated to address positioning.

From the positioning side, it may be useful to combine Stony Brook's air valve design with Marquette's structure to create supports that better conform to each individual patient. The gear idea introduced by St. Louis could be used to incorporate precise rotation.

The Rotoflex from St. Louis could be used with any of the above devices for precise positioning of the head and neck. This would be ideal for the detection of any abnormalities of the head and neck including intervertebral disk damage, vertebral fractures, and irregular intracranial pressures.

Because none of the teams addressed every component of the design problem, it may be beneficial to redefine the problem and incorporate it into the student design competition in two or three years.

Acknowledgment

This work is supported by the Rehabilitation Engineering Research Center on Accessible Medical Instrumentation, funded by the National Institute on Disability and Rehabilitation Research, U.S. Department of Education Grant #H133E020729. All opinions are those of the authors.

References

[1] Annual Report & Accounts, Amersham Market Report, 2002. [St. Louis University, Team 1]

[2] American Journal of Roentgenology, vol. 175, pp. 9-15, 2000. [St. Louis University, Team 1]

[3] "Americans with Disabilities: 2002." US Census Bureau. 20 July 2006 http://www.census.gov/hhes/www/disability/sipp/disab02/ds02t1.html

[4] American Sports Data, Inc. http://www.americansportsdata.com/.26April2006 [University of Wisconsin-Madison]

[5] Lloyd, John D. and Andrea Baptiste. "Biomechanical Evaluation of Friction-Reducing Devices for Lateral Patient Transfers." Evaluation of Friction Reducing Devices. 12 March 2003. [University of Wisconsin-Madison]

[6] CFI Medical Solutions. 9 Aug. 2006 http://www.contourfab.com/NPAs/MedVac%20System.pdf. [St. Louis University, Team 2]

[7] http://www.invivoresearch.com. [ St. Louis University , Team 2]

[8] "Student Design Competition." 2005. RERC-AMI. 9 Aug. 2006 http://rerc-ami.org/ami/projects/d/2/2/year3/

[9] Marquette University. 9 Aug. 2006 http://www.neosmultimedia.com/AccuSupport/index.htm

[10] St. Louis University, Team 1. 9 Aug. 2006 http://pages.slu.edu/org/abrilje/magi_homepage.htm

[11] St. Louis University, Team 2. 9 Aug. 2006 http://pages.slu.edu/org/greulich/HOME.htm

[12] Stony Brook University. 9 Aug. 2006 http://www.sinc.stonybrook.edu/Class/bme440/projects.htm

[13] University of Connecticut. 9 Aug. 2006 http://www.bme.uconn.edu/bme/sendes/Spring06/Team10/index.htm

[14] University of Wisconsin - Madison. 9 Aug. 2006 www.rollerpath.com

[15] Catholic University. 9 Aug. 2006 http://students.cua.edu/46nabili/PITS