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

Midmark Corporation

RECOMMENDATION OF ALIGNING TRANSFER SUPPORT WEIGHT REQUIREMENTS WITH BIFMA STANDARDS
SEPTEMBER 27, 2013

SUBMITTED BY:
Midmark Corporation (Bob Menke, committee member)

BACKGROUND

Section 5.4.11 of the Committee report makes the following recommendation:

5.4.11 Transfer Support Structural Strength Recommendations for M301 and M302

Description: Transfer supports and their connections must be capable of resisting sufficient vertical and horizontal forces to remain stable during use. The proposed provision addresses these aspects of structural strength.

NPRM Proposed Provision: M305.2.2 Structural Strength. Transfer supports and their connections shall be capable of resisting vertical and horizontal forces of 250 pounds (1,112 N) applied at all points on the transfer support.

The Committee recommends transfer supports and connections contain the strength to resist vertical and horizontal forces of 250 pounds at locations determined by the intended use of the equipment.

Rationale for the recommendation

The Committee recommends a proposal that harmonizes the transfer support requirements with other provisions for transfer supports. The proposed technical criteria originated from provisions for grab bars in the 2010 Standards. During discussion manufacturers stated that industry is required to test the most vulnerable spots on the transfer support. Industry must follow testing parameters found in other standards. IEC60601-2-52: “Transfer Supports shall be designed to withstand the forces applied during reasonably foreseeable use without creating an unacceptable RISK.” Transfer supports will deform to some degree under these loads, it must remain stable enough for use. This clause should limit elastic deformation and prohibit permanent deformation or breakage. Manufacturers of medical equipment must follow ISO14971 “Application of risk management to medical devices”, a commonly followed standard. Product development manufacturers must use risk management practices to avoid any unacceptable risk defined by the specific product designs.

RECOMMENDED CHANGE

Revise the Section 5.4.11 recommendation as follows:

The Committee recommends transfer supports and connections contain the strength to resist vertical forces of 250 pounds and horizontal forces of 125 pounds at locations determined by the intended use of the equipment.

Rational for the change:

1. ANSI/BIFMA X5.1-2011 is widely recognized and used in the furniture industry. It specifies loading as percentage of patient weight (50% vertical and 25% horizontal). So for example, an examination table rated to support a 500 pound patient would be required to hold a weight of 250 pounds vertically, and 125 pounds horizontally.

2. ANSI/AAMI ES60601-1:2005, which is the safety standard most commonly used by medical devices, requires a similar instability test in section 9.4.2.3:

ME EQUIPMENT having a mass of 25 kg or more, other than FIXED ME EQUIPMENT that is intended to be used on the floor, shall not overbalance due to pushing, leaning, resting, etc. […]

The ME EQUIPMENT is placed on a horizontal plane and a force equal to 25 % of its weight, but not more than 220 N, is applied in any direction, except a direction having an upward component. […]

If the ME EQUIPMENT overbalances, it constitutes a failure.

Note that 220 N is equivalent to 49.5 pounds of force, significantly lower than BIFMA requirements.

3. Midmark has marketed a chair arm accessory for its examination tables for over 10 years that meets a load rating of 250 pounds vertically and 125 pounds horizontally. One of the intended uses of this chair arm is to assist with patient transfer (see image below). This chair arm has proven to be robust and reliable.

4. A horizontal force of 250 pounds is unrealistic. This far exceeds the force that a person can generate in the horizontal direction under any realistic transfer scenario (see figure below). Also, because MDE is not typically anchored to the floor, it is likely that the MDE would slide across the floor before a 250 pound force could be applied.

Source: FAA Human Factors Design Standard, Chapter 14
http://www.hf.faa.gov/docs/508/docs/hfdg/ch14.doc