The assessment is the foundation for all that follows in seating and mobility. Conducting a thorough assessment that includes an interview and hands-on component, in addition to understanding the client’s desired outcomes and expectations, is the first step in determining goals for seating and mobility. Once the goals for seating have been established, generic product parameters can be selected to match the goals for seating and mobility. This month’s Clinical Corner article will review the common goals of seating and mobility and offer considerations to facilitate achieving those goals through seating. Although both the cushion and back support work together to achieve desired results, the focus of this month’s article will be on cushion selection. Back support selection based on seating goals will be the topic of a future Clinical Corner article.
Common goals of seating and mobility include:
- Pressure management
- Heat and moisture dissipation
- Vibration dampening
In addition, a combination of goals could exist. When we understand the goal or goals of seating and mobility, we can then look to generic product parameters and how they work to achieve the various goals.
Pressure management in cushions is achieved through a combination of the material(s) of the cushion base, the material and design of the cushion cover, and the product design of the cushion in how the cushion redistributes load. Other factors that contribute to pressure management in cushions are the back support taking load and consistent and effective weight shifting.
Past Clinical Corner articles have addressed these topics:
- Skin Protection and Cushion Materials. This article details the materials commonly used by manufacturers in wheelchair cushions, which include foam, elastomers, gel, fluid and air, and how the materials redistribute load. It should be stressed that there is a difference between fluid and gel in how the materials manage pressure and shear forces. This article describes the difference.
- Skin Protection and Cushion Design. The profile, or height, of a cushion will have an effect on pressure management, in addition to the generic design of the cushion (i.e., how the cushion is designed to redistribute load). This article offers insight into cushion profile and product design and their relationship with pressure management.
- Sharing a Question and an Answer. This article describes how cushion design and customization of fluid volume have an effect on pressure management in a clinical scenario. This article also shows the effect on pressure management through the cushion when the back support takes load.
- Skin Protection and Cushion Covers. Cushion covers are integral to the design of a cushion and work in conjunction with the materials and manufacturing of the cushion to help achieve seating goals. This article differentiates between stretch, microclimatic and incontinent covers, and describes how they manage pressure and shear forces.
Positioning in cushions is achieved through the contours on a cushion, modifying the material of the cushion, adding or subtracting positioning components, controlling the location and volume of fluid in a fluid cushion, or a combination of these techniques.
Past Clinical Corner articles have addressed cushion considerations for positioning:
Proximal stability affects distal function. A stable base of support takes the “work” out of sitting, which allows an individual to have greater upper extremity function and may improve sitting tolerance. To further understand the idea of the “work” of sitting, imagine you are sitting on an unstable surface, such as a large round stability exercise ball. Now imagine reaching forward, to the sides, or trying to use your hands bilaterally for a functional activity. Now imagine sitting on a firmer surface such as an office chair and doing the same reaches or activities. Functionally, it should be easier for you to complete the activities when sitting on a firm base of support. Over the course of the day, it could be less fatiguing if you are using a firm base of support.
For seating, the cushion materials and design affect forward and lateral stability. Firm material at the front of the cushion, such as dense foam, provides for forward stability. Lateral stability is affected by the presence or absence of firm material at the point of support laterally. As the Skin Protection and Cushion Design article describes, some cushions with wells are designed to float the pelvis, while some are designed to support the trochanters. When the trochanters are supported, greater lateral stability will result.
The degree to which the pelvis sinks into a pelvic loading area well on a cushion with a well will also impact stability. If the pelvis is positioned properly within the well, the femurs will take load through the firm base of support. If the pelvis is perched “on top” of the well (i.e., too much fluid volume given the size and shape of the buttocks), the cushion will not work effectively to aid in providing stability.
One final thought about function is to consider how generic cushion materials and design will work with the client for transfers and for propulsion. How will the cushion affect for transfers for the client? For example, will contours impede a sliding board transfer? If the client propels the wheelchair by foot bilaterally, are there any shearing forces that must be considered with the movement of the lower extremities and what material and product design works well with this method of propulsion?
Heat and Moisture Dissipation
Heat and moisture dissipation is another goal of seating and mobility. For some clients, this may be a secondary goal, while for other clients, heat and moisture dissipation may be a primary goal. In order to address this goal, consider the microclimate created by the various cushion materials and the cover choices.
Heat and Moisture Dissipation in Seating, a 2017 Clinical Corner article, differentiates common cushion materials into being insulators or conductors of heat. It also describes the effects of air flow within a cushion and breathability of cover materials.
Impact and Vibration Dampening
For some clients, the effects of impact and vibration must be lessened in order to permit comfort and function. For these clients, we must consider effects of cushion material on impact and vibration dampening. Air and foam are known to offer low impact transmission of vibration, while gel and fluid offer higher impact transmission. If the primary goal of seating is to lessen the impact of vibration, a cushion should be selected that is manufactured in either air or foam, or a combination of the two.
The final goal of seating to be addressed is comfort. For some clients, comfort is the primary goal of seating (for example, clients who are using seating in transport wheelchairs). For other clients, comfort is a goal that is combined with other goals, such as positioning and pressure management. It is important to remember that comfort is subjective and that what is comfortable for one person may not be comfortable for another person. It is like mattresses on beds. Some of us like a soft, squishy mattress to sleep in while others of us prefer to sleep on a firmer surface. Feedback from the client will be important to determine what is comfortable for the individual.
A final thought on comfort is that it can be measured through sitting tolerance. If someone’s level of comfort is improved, we often are able to improve an individual’s sitting tolerance, which provides an objective measure of the outcome of the intervention.
This month’s Clinical Corner article looked at six common goals of seating – pressure management, positioning, function/stability, heat and moisture dissipation, vibration dampening, and comfort. Generic product parameters, including common cushion and cover materials and product design, were identified to show how they work to help to achieve the various goals.