Recommendations on Standards for the Design of Medical Diagnostic Equipment for Adults with Disabilities, Advisory Committee Final Report

5.2 Transfer Surface Size Recommendations

5.2.1 Transfer Surface Size Recommendations for M301

Description: The transfer surface is the part of the diagnostic equipment onto which patients who use mobility devices or aids transfer when moving onto and off the equipment. Depending on the configuration of the equipment, the transfer surface may occupy only a portion of an examination table or imaging bed platform. The technical criteria do not address the overall width and depth of patient support surfaces because of the diverse shape and size of these surfaces. The transfer surface size standard has two components: width and depth (see Figure 5.2.1.1)

NPRM Proposed Provision: M301.2.2 Size. The transfer surface shall be 30 inches wide minimum and 15 inches deep minimum.

5.2.1.1 Transfer Surface Width Recommendations for M301

The Committee recommends a transfer surface of 28 inches minimum width for equipment used by patients in a supine, side-lying, or prone position.

Rationale for final recommendation

The Committee considered the initial proposal of 30 inches and ultimately decided to decrease the width proposal by two inches. Currently, the only equipment existing with a 30-inch transfer surface width is bariatric equipment.

At the Committee’s December 2012 meeting, Dr. Edward Steinfeld, Director of the Center of Inclusive Design and Environmental Access at the University of Buffalo, gave a presentation on the Wheeled Mobility Anthropometry Project (AWM Project).^GG He provided a brief analysis of measurements of the width and depth of seating surfaces for individuals using wheeled mobility devices. This study obtained data from subjects seated in their mobility devices. The results of the AWM Project indicated that a seating surface could have a width of 28 inches and accommodate the 95th percentile of the population of wheeled mobility device users studied.

As part of the deliberations, Committee members examined tables and chairs from various manufacturers during its meetings. The equipment was present and members could sit on, look at, and operate equipment during the meeting and breaks. This allowed members to experience tables that were 28 inches wide along with the other elements of the equipment.

Some supported the 28-inch dimension noting there is little gain in usability by increasing the transfer surface width to 30. The significant gain in numbers of persons able to use the equipment is at the width of 36 inches. The discussion of transfer surface width triggered the decision to set aside the issues of equipment for very large or obese patients. The Committee members expressed concern about the need to assure that persons of larger size receive care but there is incomplete data to determine specific criteria at this time.^HH

In order to have equipment with a wide enough transfer surface to accommodate very large or obese patients, the transfer surface width would need to be at least 36 inches. Since the needs of very large or obese patients are not included in this round of recommendations, the Advisory Committee agreed that either a 28 or 30 inch width would be appropriate. The Committee decided to reduce transfer surface width to 28 inches, with a future determination of equipment dimensions for very large or obese patients.

During the discussion, healthcare providers with experience in assisting patient transfers pointed out that too wide a transfer surface is challenging to smaller sized persons. Making all equipment wide enough for a 36-inch transfer surface would create difficulty for many smaller persons to transfer. For persons needing to reach across the table and pull themselves onto the transfer surface, a wider table becomes a chasm, which will impair the ability of many to grasp the side facilitating transfer. The width measurement is from the center-point of each side of the transfer surface as shown in Figure 5.2.1.1.

Figure 5.2.1.1 Measurement of Depth and Width from Center-Point of Transfer Surface Sides
(SOURCE: Midmark Corporation)

Notes

^GG Analysis of Seat Heights for Wheeled Mobility Devices. The study is available at http://udeworld.com/analysis-of-seat-height-for-wheeled-mobility-devices.

^HH Of note, the committee also decided by consensus that extreme obesity was not within the scope of the committee’s work, but to instead use the data provided by Dr. Steinfeld’s study in determining their recommendation. See section 8.1 of this report for further discussion of extreme obesity, and its recommendation for future topics of research.

5.2.1.2 Transfer Surface Depth Recommendation for M301

The Committee recommends a minimum transfer surface depth of 17 inches for all M301 except imaging equipment.

Rationale for final recommendation

Concern about the adequacy of the size of the transfer surface led members to propose an increase in the minimum depth of the transfer surface from 15 inches to 17 inches. The Committee easily supported this increase as existing equipment already encompassed this dimension.

The Committee reviewed anthropometric data from a variety of sources. Dr. Edward Steinfeld, Director of the Center of Inclusive Design and Environmental Access at the University of Buffalo, reported that his research data suggested that a depth of 15 inches would provide an adequate seating surface for the average user in his sample. However, Committee members raised concerns that the proposed depth was too short. Although the minimum size indicated by the SUNY research was 15 inches, current design practice used on tables and chairs incorporates a minimum depth of 17 inches. Some Committee members suggested that a minimum 15 inches of depth was too little, and the Committee adopted the 17-inch minimum.

This depth measurement is from the center-point of the front and back of the transfer surface as shown in Figure 5.2.1.1.

5.2.1.3 Transfer Surface Size Recommendations for Stretchers (M301)

The Committee recommends a minimum transfer surface size of 28 inches wide by 17 inches deep for stretchers located on both long sides of the stretcher.

Rationale for the recommendation

The configuration of stretchers can accommodate the same transfer surface as those used by exam tables. An important element is the position at which the patient transfers onto the stretcher. The point of entry to the equipment is in the center. The length of the stretcher means a patient would transfer on in the middle. The patient would not use the short end as the point of entry because it would require the patient to slide a long distance to lie on the stretcher.

5.2.1.4 Transfer Surface Size Recommendations for Imaging Equipment (M301)

The Committee recommends a transfer surface size on imaging equipment be a minimum of 28 inches long by a minimum of 28 inches deep. Where the 28 inches minimum depth is technically infeasible, the depth may be no less than 21 inches. The transfer surface must be located so the 28-inch long dimension is parallel to the patient scanning/imaging side of the table.

Rationale for the recommendation

The Committee agreed to this proposal to compensate for the unique aspects of the transfer surface in diagnostic equipment. Patients access diagnostic imaging tables from one of the long sides of the table. Some imaging equipment have narrow tables due to functional necessity. When patients transfer on the long side, table depth may be equal to the transfer surface depth. Lack of table depth beyond the transfer surface increases the potential for patients to “overshoot” the table during transfer, falling off the side opposite transfer. To facilitate transfers and to mitigate this fall hazard, the Committee proposes the inclusion of transfer supports (M301.3).

For equipment with bores, both long sides of the imaging table may be available for transfer subject to room layout and other imaging components. Many x-ray system tables and all DXA tables have part of the equipment support located on one of the long sides making that side of the table unavailable for patient transfer. For these types of equipment, patient transfer is only on the other side of the table.

All X-ray tables meet the 28-inch table width. However, because of physical design constraints such as bore size, not all tables used with equipment with bores meet the 28 inch width criteria but all meet the 21-inch minimum.

Manufacturers must determine the location of the transfer surface to facilitate the patient’s transfer and positioning for the clinical functions of the diagnostic procedure.

Figure 5.2.1.4 Schematic of Transfer Surface Size for Diagnostic Imaging Equipment
(SOURCE:  GE Healthcare)

5.2.2 Transfer Surface Size Recommendations for M302

Description: The transfer surface is the part of the diagnostic equipment onto which patients who use mobility devices or aids transfer when moving onto and off the equipment. Depending on the configuration of the equipment, the transfer surface may coincide with the seat area of an examination chair. The transfer surface size has two components: width and depth. (See Figure 5.2.1.1)

NPRM Proposed Provision: M302.2.2 Size. The transfer surface shall be 21 inches wide minimum and 15 inches deep minimum.

5.2.2.1 Transfer Surface Width Recommendations for M302

The Committee recommends 21 inches for the minimum width of the transfer surface of examination chairs and other equipment primarily used by patients in a seated position as described in its proposed standard 302.2.2.

Rationale for final recommendation

The Committee considered the dimensions for rectangular seats in roll-in showers from the 2010 Standards; and the ideal chair width recommended in Architectural Graphic Standards for auditorium seating. The Committee also reviewed anthropometric data from a variety of sources.

5.2.2.2 Transfer Surface Depth Recommendation for M302

The Committee recommends a minimum depth requirement of 17 inches for equipment used by patients in seated positions.

Rationale for final recommendation

As discussed in previous sections, many members expressed concern about the adequacy of the transfer surface depth. Members proposed increasing the minimum depth of the transfer surface from 15 inches to 17 inches. The Committee easily supported this increase as existing equipment already meets or exceeds this dimension.

5.2.3 Transfer Surface Measurement Recommendation for M301 and M302

Description: The transfer surface size standard has two components: width and depth. The transfer surface dimensions do not include headrests, footrests, or similar supports for body extremities that do not support the patient’s overall body position.

The Committee recommends measuring the transfer surface from the center-point of each side of the transfer surface.

Figure 5.2.3 below indicates how these width and depth dimensions are measured for MDE used by patients in supine, prone, or side-lying positions (M301) and the seated position (M302)

Figure 5.2.3 Measurement of Depth and Width from Center-Point of Transfer Surface Sides
(SOURCE: Midmark Corporation)