The ever-increasing functional capabilities of emerging medical de vices have precipitated new requirements for the multi-function foot controls used to operate the equipment. These foot controls typically consist of multiple actuators, one for each required control function.

Fig. 1 – Surgical microscope foot control.
For example, it is not uncommon to find foot controls for electrosurgical generators with three functions, foot controls for endoscopic surgical apparatus with five or six functions, cataract surgery systems requiring six to nine control functions, and surgical microscopes requiring 10 or more functions.

This increasing foot control complexity has placed new challenges on the manufacturer to offer and produce foot controls that are easy to navigate and easy to use. Optimum usability requires creative ways to quickly locate the foot control unit and each of its functional actuators.

To address these challenges, visual and non-visual aids can, and are, being designed into medical-grade foot controls to enhance their usability. Visual navigation aids include the use of different actuator types; different actuator colors; the use of graphics, text, and internationally recognized icons; and lighting. Non-visual navigation aids include the use of foot rests or landing pads; protection braces/carrying handles; console geometries that facilitate easier/intuitive actuator location; and actuator geometry/location.

Visual Navigation Aids

Fig. 2 – Biopsy sampling system foot control.
Actuator Styles: One visual tool for aiding in navigation is the use of different types of actuators for differentiating between various control functions. Medical device OEMs can choose between a wide selection of actuator types/styles including: pedals, rocker-style switches, push buttons, joy sticks, joy pads, and custom-designed actuators.

These choices may be influenced by their basic control function (e.g., on/off vs. proportional control) and/or their frequency of use during a specific procedure. Table 1 provides a brief review of these choices and a sampling of typical applications for each.

Figures 1 and 2 show the use of these .actuators in a selection of medical device applications. In Figure 1, the joystick enables the positioning of the microscope in the surgical field (X-axis and Y-axis). Two rocker switches provide focus and zoom control. Push-button actuators at the four corners provide light control of dimming and brightness for optimal contrast, an on/off light switch, and a camera control to capture a desired image. In Figure 2, which shows a biopsy sampling system foot control, the foot rest provides a convenient “touch point’ for easily locating the pedal and push-button functions providing easy management of sample acquisition.

Fig. 3 – High-frequency electrosurgical generator foot control.
Color, Graphics, Text, and Icons: Another effective technique for enhancing user-friendliness is the use of color and graphics to identify the specific function performed by each actuator. For example, the use of blue and yellow pedals is standard to identify the “cut” and “coagulation” functions on foot controls used with high-frequency electrosurgical generators (See Figure 3). Often, functions are identified through the use of text, graphics, and/or easily recognized icons.

Lighting: Some applications require the use of a foot control in a darkened or low light environment. In such instances, foot controls can be equipped with LEDs that cast a “glow” around the unit to allow the user to more easily locate it on the floor. Depending upon the design of the foot control console, the LEDs may be located such that they are not visible via a direct line-of-sight. Here they simply provide a soft glow that is quite visible when ambient light is low.

Non-Visual Navigation Aids

Some users may prefer aids that enable them to locate or navigate without the need to look at the foot control, without having to take their eyes from the surgical field, or from a computer display. To accomplish this, a number of tactile techniques are available. These may include any of the following.

Foot Rests/Landing Pads: This is simply an area provided on the foot control console where the user can rest his or her foot until the next control action is required. With this as a reference point, the operator can (after becoming familiar with the unit) move a foot to the desired control actuator without the need to look away from the procedure. Located at the center of the console, between two actuator pedals, the user simply moves a foot left or right to initiate the desired control function (See Figure 3.).

Physical Reference Surfaces: Another effective technique is the use of physical reference surfaces designed into the unit. This can be seen in Figure 3. Here the height of the console’s outer left and right sidewalls enable the user to simply move a foot right or left to determine on which of the two pedals they are. Thus, regardless of where the operator’s foot is at any given moment, it is easy to determine its location without looking down.

Carrying Handles/Protection Braces: One example of this optional accessory is shown in Figure 2. Such “handles” not only serve as a footrest and point of reference, but also allow an easy means of picking up and carrying the foot control (thus eliminating possible damage to the cable at the strain relief). In some laser-based device applications, they also serve as a recognized and acceptable protection guard against inadvertent operation in accordance with IEC 60601-2-22.

Depending upon the design of the handle, it can also serve as an easy means of moving the foot control during the procedure. This is accomplished simply by using one’s instep to lift the unit and reposition it (without having to reach down or touch the unit during the procedure).

Such handles can often be designed to be collapsible, for example, to fold down upon release of an integral mechanical latch. Doing so reduces the overall height of the unit for easy storage on a cart’s docking station or in a cabinet.

Console Geometry: Depending upon the application, and its control requirements, the basic foot control console, which serves as the host for the control actuators and provides the wiring compartment for accommodating the electric/ electronic components, can be designed to assist with navigation. One example is the angled console shown in Figure 4.

Designed for use in phacoemulsification cataract surgery, which uses an ultrasonic device to break up and remove a cataract from the eye, followed by the insertion of an intraocular lens, this foot control unit features a bidirectional pedal (X and Z axes) capable of analog or digital control, and four push-buttons located at the four corners of the console—toe left, toe right, heel left, and heel right. This pattern allows for easy selection of the appropriate control function from the rest position on the pedal, or from the touch point at the base of the unit. After just a few uses, the operator will easily be able to locate and actuate each of the specific control functions by touch.

Summary

Fig. 4 – Phacoemulsification cataract surgery foot control.
As new medical devices continue to be developed, their capabilities may require the use of multi-function foot controls. If so, the medical device OEM has the luxury of providing integral navigation aids, while satisfying their functional, ergonomic, and aesthetic foot control needs with a wide selection of “off-the-shelf” consoles, actuators, handles, colors and graphics assembled into a “customized’ solution, without the need for non-recurring engineering development costs or tooling investments. Or, if desired, they may optimize usability with a fully-customized design that addresses the device’s functional, ergonomic, and aesthetic needs with new style actuators, or other custom accessories.

Since the foot control is often the primary user interface gating the customer’s experience, considering and implementing some navigation aids at the start can optimize the medical device’s usability and enhance the user’s experience.

This article was written by Peter M. Engstrom, Managing Director, and Maurizio Lauria, Product Manager, Steute Meditech, Inc., Ridgefield, CT. Steute, founded in 1961 in Löhne, Germany, is focused exclusively on the development and production of medical grade foot switches for device OEMs. For more information, Click Here 


Medical Design Briefs Magazine

This article first appeared in the February, 2013 issue of Medical Design Briefs Magazine.

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