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

4.1 Examination Tables and Chairs

4.1.1 Range of Examination Table and Chair Configurations

Examination tables and chairs are used wherever patients are examined throughout the health care delivery system. Therefore, tables and chairs must support a wide range of diagnostic activities, clinical indications, and patient populations. These demands have implications for the design, configuration, and principles of operation of examination tables and chairs. Broadly speaking, this equipment falls into two categories based on the positioning of the patient undergoing examination, those encompassed by the M301 and M302 criteria of the U.S. Access Board’s NPRM for MDE accessibility (see Section 1.3.1 and Tables 1.3.1(a) and 1.3.1(b)):

1. Equipment designed for patients in prone or side-lying positions (M301)

• Examination tables

• Podiatry tables

2. Equipment designed for patients seated or in semi-supine positions (M302)

• Examination chairs

• Dental chairs

• Optometric chairs

• Otolaryngology (ENT) chairs

• Phlebotomy chairs

• Podiatry chairs

As noted in the NPRM for MDE accessibility standards, when equipment is designed to support more than one patient position, the equipment would have to meet the technical criteria for each position supported. The word “prone” describes persons “lying on their stomachs” or “fronts” – in more technical language, in a ventral position. “Supine” indicates persons lying on their backs or with their faces facing upward. There are many positions between prone and supine, indicated by such terminology as semi-supine, Fowlers, semi-Fowlers, and semi-recumbent. For setting standards, these intermediate positions might be best considered in the M302 criteria. Some examination tables can be configured to have patients in either prone or seated positions (both M301 and M302 standards). Manufacturers design examination chairs that have, as their primary function, the support of patients in a seated or semi-supine position. While some chairs are capable of fully reclining, this is a secondary rather than primary functionality. In general, examination chairs are not designed for use in the prone or side-lying position.

4.1.2 Surface Design of Examination Tables and Chairs

For several reasons including patient comfort and safety, the surfaces of many examination tables and chairs are not flat. Instead, they are contoured, such as by using bolsters along the perimeters, to provide greater security once patients are lying or seated on the table or chair. This contouring complicates efforts to measure the distance between the floor and the height of the surface onto which patients transfer for their examinations. Thus, contouring must be addressed in considering minimum height standards for accessibility of transfer surfaces (Section 5.1.4).

As noted in Section 2.4.1, the height measurement method recommended by the Advisory Committee (Section 5.1.4) differs from the heights that manufacturers publish today. Currently, the de facto industry practice is to publish table or chair heights as measured while patients are seated on the equipment (i.e., while patients’ weights are compressing the table’s or chair’s foam padding).^Z This dimension is typically measured at the back of a patient’s knees and includes compression of the seat foam. This method is consistent with the internationally recognized standard for the measurement of wheelchairs, ISO 7176-7:1998.

In contrast, the Advisory Committee recommends that measurement be taken from the highest point of the transfer surface, irrespective of contours, and with uncompressed foam (Section 5.1.4). Committee members recommend this measurement method because it ensures that the entire transfer surface is below the recommended height. This allows patients to choose the transfer location and technique that best meets their individual needs. For consistency, all transfer surface height measurements referenced in this report use the measurement method specified in Section 5.1.4, unless otherwise noted.

Notes

^Z Seated height became the de facto height measurement method because this height is most relevant to clinicians as they conduct physical examinations of patients.  Consequentially, health care professionals who are purchasing examination tables and chairs typically focus on the seated height dimension.

4.1.3 Adjustable Height Chairs with and without Footplates

Patients seated in adjustable height examination chairs typically rest their feet on the floor or on a footplate or have their feet hang with support from the lower portion of the chair. Because these chairs with footplates are adjustable in height, when the chair height is fully lowered, a minimum 2” clearance is required from the floor to the bottom of the footplate as specified by domestic UL and International Electrotechnical Commission (IEC) standards (as currently designed, footplates themselves are 1” thick at a minimum). For chairs without footplates, patients place their feet on the floor, but the retracted leg rest must maintain the same 2” clearance from the floor. Anthropometric data suggest the heel to popliteal dimension without shoes of males is 17.5” and of females is 15.9” at the 50th percentile. Current chair configuration and anthropometric factors inform the implications of minimum height standards for accessibility of chair transfer surfaces for future designs (Section 5.1.3).

The positioning of patients’ feet in relation to their seat height has critical implications for their comfort, as suggested in Figure 4.1. Contact with the back of the thigh and/or the rear of the knee with the top front portion of the seat is vital for patients’ comfort. This is especially important for maintaining the knee and thigh positions of individuals with disabilities who have difficulties controlling their lower extremities. If the distance between the footplate and the seat is too short (due to the required clearances described in the preceding paragraph), patients with disabilities could be uncomfortable during their diagnostic examinations and also have problems keeping their legs properly positioned.^AA

For those chairs that transform into examination tables, reducing the distance between the floor and seat height may also restrict the overall length of the table when the patient is reclined into a supine position. Figure 4.1 shows the chair when configured in an upright seated position; these same patient support surfaces (made up of the back, seat, and leg rests) are repositioned horizontally to create a supine patient support surface. Therefore, a shorter leg rest results in an overall shorter horizontal table top. Some knee break chairs available in the market today have a total length of around 60”; with the addition of a flip-up or slide out footrest/leg rest extension, this total length increases to approximately 68”. Manufacturers expressed concern that reducing seat height will further reduce these table lengths, affecting the ability to adequately support patients in the supine position.

Figure 4.1

Anthropometric Data and Concept Drawing:
Support at Lower Thigh/Back of Knee for 17” and 19”
Distances between Footrest and Seat Heights

(SOURCE: Medical Technology Industries, Inc.)

Notes

^AA For adjustable height chairs with footplates, as the height of the chair seat (transfer surface) moves up and down, the footplate moves up and down at the same time (i.e., with a fixed vertical distance between the seat and footplate). Therefore, reducing the low height of the seat will increase the likelihood of the footplate colliding with the floor.  However, shortening the vertical distance between the seat and the footplate could result in the uncomfortable body positions shown in Figure 4.1.