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Does Wheelchair Cushion Design Affect its Performance?

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Today’s wheelchair cushions are expected to perform several major functions:

  • Comfort
  • Positioning
  • Protection against pressure wounds

The wheelchair cushion is a relatively small part of the overall wheelchair as it relates to size and weight, however it is critical to the performance of the entire seating and mobility system. Cushion manufacturer’s invest a great deal of money and time into creating cushions with contours, cut-outs, profiles and bladders using a host of different materials.

HOW DOES MEDICARE CATEGORIZE CUSHIONS?

Medicare identifies wheelchair cushions into four major categories: general use, skin protection, positioning and skin protection & positioning. They then sub-categorize the cushions according to size and adjustability or lack thereof. Manufacturer’s wanting Medicare to recognize their cushions for reimbursement apply for HCPCS codes. The manufacturer’s application for acceptance must provide Medicare with information as to the components and accessories included in the product, including how the cushion provides acceptable weight distribution, how it is to be used and the media contained within the cushion. Their application must be accompanied with sufficient test results to back-up their claims.

Medicare’s basic criteria for a general purpose wheelchair cushion is how well it envelopes a client’s body and to make sure that the cushion does not bottom out on those whose weight is less than the manufacturer’s stated weight limit.

For cushions applying for skin protection and/or positioning codes, the testing becomes more complex. Not only do the contour depth and the components for skin protection need to meet Medicare requirements, but the cushion must also have positioning components. The positioning components include a pre-ischial bar or ridge in front of the ischial tuberosity’s to prevent forward migration and lateral pelvic supports. Additionally Medicare will look for the cushion to have a medial thigh support, a certain height at a preloaded state including the planar surface and other features that make the material firmer within the cushion.

An adjustable cushion must meet all the criteria for skin protection as well as have the ability to adjust the depth that the client sits in the cushion with proper pressure redistribution. Many cushions do these adjustments with air or another fluid such as a liquid gel. EquaGel cushions make the adjustments with two inserts that are placed in a pocket under the pelvic contour.

A quality wheelchair cushion has to effectively perform pressure management

  • Evenly distribute the user’s weight across the cushion,
  • Assist in positioning,
  • Provide stability and
  • Absorb vibration and impact.

Traveling with a wheelchair cushion presents other problems. If one takes an air cushion onto an airplane the air is going to expand from the lower pressure in the cabin. Therefore, air will need to be released from the cushion during the flight. Upon landing, air will then have to be added to the cushion to readjust the cushion to the proper inflation level.

IS FUNCTION IMPACTED BY DESIGN?

Should the cushion be flat? Should it have a contour or profile? Maybe it should be constructed with multiple-media. Does a high-profile cushion work better than one that is low-profile?

The primary reason for a contoured cushion is for pressure distribution. The more closely that the cushion shape matches the client’s body contour, the more surface area is involved in the pressure distribution and the more one is immersed into the cushion. Contours also help in the positioning of the legs and pelvis.

Most pre-contoured cushions are designed to fit the majority of the population. However, that does not mean that they will fit everyone. Therefore it is important that the contour fit the person well in order to function effectively.

High profile or low profile? The choice of the height of the profile not only applies to pressure distribution, it also adds the element of stability. Cushions made of foam, air or a liquid that offer a high profile will usually provide more room to immerse into them. However a taller cushion may make the user feel less stable.

Lower profile cushions typically will provide more stability and may respond more efficiently to even minor input. Many wheelchair users feel they have more control over their movements with a low-profile cushion.

Many cushion manufacturers have begun using multiple media within a single cushion. For example a gel fluid cushion is very heavy and does not maintain any shape. As such, manufacturers may incorporate a stiffer foam base to provide the required cushion shape. The use of foam may also reduce the overall cushion weight.

Also some manufacturers combine air and foam. The air cushion is assumed to provide some protection for the skin and the foam is for positioning and stability.

You will also find some foam cushions that incorporate various thicknesses and/or densities of foam to provide comfort and positioning.

WHICH CUSHION IS BEST?

With all the choices that are available which is best? Not everyone will have the same priorities. Most people with a spinal cord injury will probably experience a decubitus ulcer sometime during their life. As such, skin protection will definitely be a priority. But that may not be the only priority. For those with a higher level of spinal cord injury that do not have any trunk control, positioning and stability will also be important. Therefore, one needs to identify a cushion that can provide both protection and stable positioning.

For someone with cerebral palsy, skin protection may not be the major issue but positioning and stability are still required.

For all users, it is important that they experience effective pressure distribution without hitting bottom on the cushion. Hitting bottom on a cushion will first make the client uncomfortable as there will be continuous pressure against their pressure points (most commonly the ischial tuberosity’s and/or coccyx). Continuous pressure against ones pressure points may eventually cause pressure wounds to form. Dry polymer cushions that incorporate the buckling column design do not bottom out at any weight.

The goal of all the choices among the various cushion types is to provide seating specialists with a large arsenal of potential solutions for their clients – all with varying individualized needs.

HOW DO WHEELCHAIR CUSHIONS COMPARE?

 

SEATING PRIORITIES FOAM CUSHION AIR CUSHION AIR/FOAM LIQUID GEL/FOAM EquaGel Cushions
Pelvic Contour assists with positioning/Stability Good Better Better Better Best
Weight Limit Yes Yes Yes Yes No
Bottom Out Yes Yes Yes Yes No
Relief for Ischial Tuberosity’s Good Better Better Good Best
Relief for the Coccyx Good Better Better Good Best
Temperature Neutral Poor Good Good Poor Best
Aids in Protection against Pressure Wounds Good Better Better Good Best
Helps Existing Pressure Wounds to Heal Good Better Better Good Best
Extended durability that includes full resiliency Poor Better Better Good Best
Buckling Column Design None None None None Yes

Despite all the cushion choices available, one has to match the various characteristics of a cushion with the priorities of the user. Some cushions perform better than others. The most important criteria is to match the user’s needs with the cushion that best meets those needs.

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