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

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.