Key attributes of a wheelchair seat cushion

When determining the best solution for an individual, a thorough assessment is required by an experienced physical or occupational therapist. In this assessment the therapist will take a wholistic view:

With the wholistic assessment, a therapist can establish goals based on evidence-based practice. The 2019 Clinical Practice Guideline recommends selecting a seat cushion and wheelchair that:

• Minimizes the pressure and shear exerted on the skin and soft tissue at high-risk areas
• Provides adequate support​
• Maintains stability​
• Maintains the individual’s full range of activities​

Considering the Clinical Practice Guideline and clinical reasoning, Permobil believes there are three key attributes of a cushion that should be considered in meeting wheelchair seating system goals:

Skin Protection

Stability

Positioning

The attributes directly reflect the CPG recommendations:

Skin Protection

Being seated full time automatically means that skin protection is required. However, there are varying needs for skin protection among full time wheelchair users based on various factors: the ability to perform frequent pressure reliefs, the ability to reposition, and the condition of the skin based on disease process, nutrition, or years since injury. Permobil understands the importance of skin protection and has designed products for almost every level of need utilizing the highest quality mediums, design, and technologies.

A key component of preventing pressure injury or promoting healing is through optimal pressure distribution. There are three methods of pressure distribution that are important to understand when evaluating a cushion:

Immersion: to submerge/sink into a surface

Envelopment: to surround the object being submerged

Offloading: redirecting pressure away from a small surface area to a greater surface area that can tolerate more pressure

Stability

A seat cushion can be considered the foundation of the seated posture. Having a stable base means the postural muscles don’t have to work as hard to keep an individual upright. For an abled bodied individual this isn’t obvious because they are able to shift positions frequently adapt to various positions and maintain an upright posture. When the postural muscles have been impaired through injury or disease, suddenly the base of support becomes very important. The goal is to decrease the work required of the postural muscles by providing a stable surface, maximum support, and stabilization of the pelvis. Permobil offers cushions that have various levels of stability to meet the needs of most individuals using a wheelchair. Our goal is to provide individualized stability to promote function and participation in activities at the highest level.

Positioning

There are no two postures alike! We understand this at Permobil and have designed cushions and technologies that can accommodate various positioning needs of an individual. Whether through immobility, injury, or disease processes wheelchair users can sometimes have atypical postures and/or limits of range of motion that impact their ability to sit upright and be functional without risk of developing a pressure injury. Permobil understands this and offers products with varying degrees of positioning capabilities to accommodate the needs of most individuals.

An overview of the portfolio

Since individuals have unique seating goals that may not require every attribute, our extensive portfolio includes cushions with materials and technologies that allow Permobil to offer solutions for most individuals. We will take a look at each product line and show how they uniquely address the various attributes of great seating.

Foam Products

Comfort cushioning products are foam based cushion solutions designed with the use of pre-contoured shapes, quality materials and superior cover designs. Comfort cushions were engineered to match the anatomical shape of the human body. Each contour and shape has countless hours of research and uses biomechanical principles to aid in the design of the product.

Not all foam is alike. Strategically layering different types of High Resiliency (HR) quality foam, Comfort cushions provide a stable base, have the ability to withstand compression over time and provide mild immersion for the individual’s body.

Air Products

Air: Flowing

The unique air-cell design of the ROHO^® cushion range has the capability to conform and adapt to an individual's body shape, mimicking the pressure redistribution properties of water.

Four Fundamentals of a ROHO® Dry Floatation® Cushion:

• Lets you in (low surface tension): Our unique design lets you easily sink into the cushion, reducing pressure and discomfort to your skin and soft tissues.
• Matches your shape (constant restoring forces): Your shape is unique. A ROHO cushion constantly conforms and adapts to you and can be adjusted to your body changes over time.
• Moves with you (six degrees of freedom): No matter what you are doing, your ROHO cushion will adapt to your every position throughout the day and over time. The air cells follow your motions, giving you support and freedom of movement.
• Works with you, not against you (low friction and shear): Nothing feels like a ROHO cushion. The smooth surface reduces shear and friction without compromising your safety and comfort.

Air: Non-Flowing

Vicair^® Technology* uses individual air filled “SmartCells” – which offer a unique combination of skin protection and positioning. SmartCells together form layers within the compartments of the cushion. Within the compartments, SmartCells move with little friction; they mimic a viscous fluid, enabling the cushion to adjust to the shape of the body. Cushion compartments are designed in such a way that provide stability and therefore provide positioning. Each compartment is filled with just the right amount of SmartCells, resulting in a stable cushion. Each compartment can also be adjusted to fit individual needs by removing or adding SmartCells.

Hybrid Products: Foam/Air, Foam/Gel

Hybrid products are a combination of either foam and gel or foam and air. Typically, a High Resiliency (HR) foam base is used as the foundation, providing the shape and contours of the cushion. Then flowing air, non-flowing air or gel packs are placed in high risk areas.

Overarching view of evidence

Quality and efficacy are the key foundations of Permobil. To demonstrate how Permobil cushions perform, we rely on a range of evidence and best practices, including

• Clinical reasoning and published clinical evidence
• Mechanical data from standardized bench testing (ISO and RESNA)
• Current clinical practice guideline (CPG) for the prevention of pressure injuries

The design, development, and evolution of our cushions are informed by all these perspectives, and these globally recognized knowledge and testing sources provide insight into how each cushion is unique, and how each cushion brings different benefits.

Permobil professionals are at the forefront of the state of standardized bench testing and clinical practice, through participation and leadership in the NPIAP, ANSI/RESNA, ISO and CEN.

We continuously test our cushions to ISO and ANSI/RESNA standards at the Tissue Integrity Management Laboratory at the University of Pittsburgh, global leaders in wheelchair & cushion performance testing standards. Learn more, and see the tests for yourself: https://wheelchairstandards.com/

Having this range of evidence and information helps with the cushion selection process to meet the needs of an individual. Like every individual, each cushion is unique. Find the one that works best for them.

Standardized Bench Tests

Scientific tests performed in a controlled laboratory environment to objectively measure and compare/contract cushion properties.

The ISO standards for cushions measure properties that are important for preventing pressure injuries and providing seated stability. They measure the support surface properties recommended by the NPIAP Clinical Practice Guideline.

The five standardized bench tests measured were:

• Immersion
• Slide Resistance
• Shear Force
• Contact Area
• Lateral Stability

Is it important for a product to test well in all areas?

Each individual will have needs and goals that are trying to be met. Look for a product that performs well in the area(s) that meets their individual need(s). For example, if an individual has trunk weakness and has difficulty sitting upright over time, choose a cushion that tests well in lateral stability.

Considering the three attributes of great seating, let's take a look at these standardized bench tests in greater detail.

Skin Protection

Standardized bench tests: immersion, shear force, and contact area

Immersion

(US PDAC Test) ISO 16840-2

How deeply does the body sink into the cushion?

Clinical Significance: NPIAP recommends immersing more than 40mm to cradle bony prominences, which may reduce the risk of pressure injury.

Immersion Bench Test Results: Click to see how Permobil cushions perform in the immersion bench test.

Shear Force

How much are the tissues being tugged at the ITs?

Clinical Significance: Lower shear forces minimize the tissue distortion/deformation and may reduce risk of pressure injury.

Shear Force Bench Test Results: Click to see how Permobil cushions perform in the shear force bench test.

Contact Area

Pressure Mapping ISO 16840-6

How well is force from the body being managed by the cushion?

Clinical Significance: Achieve as much contact area as possible to promote greater pressure redistribution which may reduce risk of pressure injury.

Contact Area Bench Test Results: Click to see how Permobil cushions perform in the contact area bench test.

Stability

Standardized bench test: lateral stability

Lateral Stability

ISO 16840-13

How well is the body held in place during a lateral move? How much counter pressure is coming back to the body?

Clinical Significance: A more stable cushion during leaning may increase ability to perform daily tasks for individuals with trunk and/or pelvic weakness.

Lateral Stability Bench Test Results: Click to see how Permobil cushion perform in the lateral stability bench test.

Positioning

Standardized bench test: slide resistance

Slide Resistance

Horizontal Force ISO 16840-2

How easy is it to slide forward in the cushion?

Clinical Significance: A higher force indicates more stability and may contribute to decreasing forward migration of the pelvis in the cushion for those with trunk and or/pelvic weakness. The ideal is higher horizontal stiffness with low shear.