Wheelchair Cushions and Pressure Relief Explained: A UK Expert Guide

Why Your Wheelchair Cushion Matters More Than You Think 

If you use a wheelchair regularly, your cushion isn't just about comfort—it's a critical piece of medical equipment that protects your health. Many people don't realise that sitting in one position creates enormous pressure on small areas of skin and tissue. Without proper support, this pressure can cut off blood flow and lead to serious complications called pressure ulcers.

In the UK, pressure ulcers cost the NHS hundreds of millions of pounds annually to treat. More importantly, they cause significant pain and can lead to hospitalisation. The good news? The right wheelchair cushion, properly fitted and maintained, dramatically reduces this risk whilst improving your daily comfort and quality of life.

Understanding Pressure Ulcers: The Silent Danger

Pressure ulcers—sometimes called pressure sores or bedsores—occur when sustained pressure damages the skin and underlying tissue. When you sit, your body weight concentrates on remarkably small areas: primarily your ischial tuberosities, commonly known as your "sit bones." These are the two bony prominences at the base of your pelvis.

The problem arises when pressure at these points exceeds what's called the capillary closing pressure, typically around 32 mmHg. When this happens, the tiny blood vessels that deliver oxygen and nutrients to your skin cells collapse. If this continues for too long, cells begin to die—a process called necrosis—and an ulcer forms.

What makes pressure ulcers particularly insidious is that damage often starts deep inside the tissue, near the bone, before you see anything on the skin surface. By the time you notice a problem, significant harm may have already occurred.

The Hidden Threats: Shear, Friction, and Moisture

Whilst pressure gets most of the attention, three other forces work together to damage skin:

Shear is often the most dangerous force, yet the least understood. Imagine your skin stays stuck to your cushion whilst your bones and deeper tissues slide downward—perhaps when you slump or slide forward in your chair. This creates a stretching force that kinks or tears the blood vessels connecting your deep tissue to your skin. The damage occurs from the inside out, which is why shear injuries can look like bruises initially but then open into large, deep wounds.

Friction acts like a carpet burn, stripping away the protective outer layer of skin. Whilst friction alone typically causes surface damage, it leaves skin vulnerable to pressure and infection.

Moisture from perspiration or incontinence is the final piece of the puzzle. When skin stays damp, it weakens and breaks down more easily—a process called maceration. This makes already vulnerable tissue even more susceptible to pressure damage.

Quality wheelchair cushions are engineered to address all four of these threats simultaneously, not just provide a softer seat.

Assessing Your Risk: Do You Need Specialist Seating?

In UK healthcare settings, professionals use validated risk assessment tools to determine who needs pressure care equipment. The most common is the Waterlow Score, which assigns points based on your build, skin condition, mobility level, and special risk factors like neurological conditions or incontinence.

The scoring breaks down as follows:

• 10+: At Risk

• 15+: High Risk

• 20+: Very High Risk

If a district nurse or occupational therapist has mentioned a Waterlow score to you, it's a guide to the level of cushion technology you need. Someone scoring 12 might manage well with a quality foam cushion, whilst someone scoring 22 likely needs an air flotation system.

Even without a formal assessment, you can gauge your own risk. You're at higher risk if you:

• Spend more than 4-6 hours daily in your wheelchair

• Have limited ability to shift your weight or reposition yourself

• Have reduced sensation in your buttocks or legs

• Have a history of pressure ulcers

• Are very thin (bony) or significantly overweight

• Have diabetes, circulation problems, or neurological conditions

• Experience incontinence or heavy perspiration

The Science of Seating: Types of Cushions Explained

Choosing a cushion means understanding how different materials solve the pressure problem. Each technology has distinct advantages suited to different risk levels and lifestyles.

Foam Cushions: Stability and Comfort for Low Risk

Standard foam cushions are the baseline for wheelchair seating. High-density polyurethane foam provides a stable, firm surface excellent for transfers—you can push down on it to stand or shift position without the sinking feeling of softer materials.

For pressure relief, foam works by increasing the contact area between your body and the seat, spreading your weight over a larger surface. However, basic flat foam offers limited pressure redistribution compared to more advanced technologies.

Memory foam (visco-elastic foam) takes this further by moulding to your body's exact contours. It flows away from high-pressure points, creating better immersion. The trade-off? Memory foam acts as an insulator, retaining body heat. In warm weather or for heavy perspirers, this can create moisture problems that compromise skin integrity.

High-end foam cushions use contoured designs with a pelvic "well" and shaped femoral channels for the thighs. This mechanical shaping helps maintain proper posture and prevents the forward sliding that creates dangerous shear forces.

Best for: Active users at low to medium risk who prioritise stability, particularly those who transfer frequently or have good core strength.

Gel Cushions: Specialist Solutions for Shear and Cooling

Gel behaves remarkably like body fat—it's a semi-solid material that allows bony prominences to sink in whilst providing support. The critical advantage of gel is its ability to move with your skin, significantly reducing shear forces. When you shift position slightly, the gel flows, preventing that dangerous stretching of blood vessels.

Gel also has excellent thermal properties. It takes longer to heat up than foam, providing a cooling effect that many users find comfortable and which helps maintain healthy skin temperature.

Most "gel cushions" are actually hybrids: a foam base provides structural stability for transfers, whilst gel bladders or inserts position directly under the sit bones for pressure protection. This engineering gives you the best of both materials—stability where you need it, protection where it matters most.

The downsides? Gel cushions are heavy, which can make your wheelchair harder to push and more difficult to lift into a car. If a fluid gel bladder punctures, it's a complete failure requiring replacement.

Best for: Medium to high-risk users who need excellent shear protection, particularly those with some pelvic obliquity (uneven hips) or who tend to slide forward in their chair.

Air Cushions: The Gold Standard for High Risk

Air cushions represent the pinnacle of pressure care technology. Systems like ROHO or Vicair use interconnected cells filled with air. When you sit down, air flows between cells to equalise internal pressure, allowing you to sink deeply (immersion) whilst the cushion surrounds your buttocks (envelopment).

This creates what engineers call "dry flotation"—mimicking the pressure distribution of floating in water. Because air is fluid, pressure equalises across every point of contact, eliminating pressure peaks at the sit bones.

Air cushions offer another crucial advantage: adjustability. They can be tuned precisely to your weight and body shape. For users with asymmetrical bodies or spinal curves, air cushions accommodate these differences rather than forcing correction.

The challenges with air cushions include:

Stability: That floating sensation can feel unstable, particularly for users with limited core strength or balance issues. Some people find transfers more difficult.

Maintenance: Proper inflation is critical. Under-inflate and you "bottom out," sitting directly on the hard base—worse than no cushion at all. Over-inflate and you sit on top of the cells rather than sinking into them, losing the pressure distribution benefits.

Puncture risk: A slow leak gradually reduces effectiveness, whilst a sudden puncture renders the cushion useless until repaired.

Modern air cushions address some stability concerns through compartmentalised designs. ROHO's ISOFLO Memory Control, for instance, locks air into four quadrants, preventing it from all rushing to one side when you lean. Vicair uses hundreds of small "SmartCells" instead of large interconnected chambers—if one punctures, the cushion continues functioning.

Best for: High to very high-risk users, particularly those with existing pressure damage, complete immobility, or spinal cord injuries with no sensation.

Dynamic and Alternating Systems: Critical Care Solutions

For users with existing Grade 3 or 4 pressure ulcers, or those completely unable to reposition themselves, dynamic cushions take a different approach. Battery-powered pumps cyclically inflate and deflate different rows of cells. For portions of each cycle, pressure is completely removed from specific skin areas, allowing blood flow to return.

This active "off-loading" mimics the pressure relief your body naturally achieves by shifting position—but does it automatically for users who cannot move themselves.

These systems are heavy, expensive, and produce pump noise. They're prescribed for very high-risk situations, often as part of ulcer treatment rather than prevention.

Best for: Very high-risk users, often with existing wounds, who require maximum intervention.

Choosing the Right Cushion: Practical Guidance

Getting the Fit Right

A cushion that doesn't fit properly is not just uncomfortable—it's dangerous. Width and depth must match your wheelchair seat dimensions precisely. Too narrow and your hips contact the wheelchair's side rails, creating new pressure points. Too wide and the cushion overhangs, deforming under your weight or making your chair too wide for doorways.

Height matters enormously. Adding a thick cushion raises your sitting position, which affects everything from your ability to reach the push rims to whether you can fit your legs under a table. Footrests must be adjusted downward to compensate, maintaining proper hip and knee angles.

Professional measurement by an occupational therapist is ideal, but if you're purchasing privately, measure carefully: sit in your wheelchair and measure from hip to hip (width) and from the backrest to the front of your thighs (depth). Most reputable suppliers, including ourselves at Mobilityshop, can guide you through this process.

The Hand Check Method: Essential for Air Cushions

If you use an air cushion, learn this simple but critical check. It prevents "bottoming out"—the dangerous situation where you're actually sitting on the hard base rather than floating on air.

Here's how:

1. Sit on your fully inflated cushion in your normal posture

2. Have someone slide their hand, palm up, under your buttock, searching for the lowest bony point

3. There should be 1.5 to 2.5 centimetres (roughly half an inch to one inch) between your bone and the cushion base

4. If fingers can't move or feel pinched, add air

5. If there's too much space (more than an inch), release some air

Check this weekly, and always check after long periods of storage, as air pressure changes with temperature.

Managing Moisture and Microclimate

Perspiration is more than just uncomfortable—moisture weakens skin's structural proteins, making it dramatically more susceptible to pressure damage. If you're a heavy sweater, prioritise cushions with breathable covers. Three-dimensional "spacer fabric" covers allow much better airflow than vinyl, though they're not waterproof.

For incontinence, waterproof covers are non-negotiable to protect the cushion interior. However, this reduces breathability, making meticulous hygiene even more critical. Air cushions naturally promote airflow between cells, making them an excellent choice if moisture is a concern.

Cleaning protocols:

• Covers: Most are machine washable at 40-60°C

• Foam: Never submerge. Wipe with mild detergent and allow to air dry completely

• Air cells: Hand wash in a basin with mild soap, rinse thoroughly, and air dry—never tumble dry

• Gel: Wipe the bladder exterior; never puncture or immerse

Recognising When to Replace Your Cushion

Cushions don't last forever, and a worn cushion provides false security—you think you're protected when you're not.

Foam cushions: Last 1-2 years typically. Press firmly into the main wear area—if it doesn't spring back quickly, or if you see crumbling, discolouration, or permanent compression marks, it's time to replace.

Gel cushions: Expect 2-3 years. Check for hardening of the gel or migration (where gel has moved away from pressure areas and won't flow back).

Air cushions: Can last 3-5 years or more, but valves and rubber degrade. Frequent leaks or difficulty maintaining pressure signal end-of-life.

Expert Maintenance Tips

Daily visual inspection: Before sitting, check your cushion for obvious damage, proper inflation (for air types), or deformation (for foam/gel types).

Skin checks: Examine your pressure areas daily using a mirror if needed. Look for persistent redness, heat, swelling, or changes in skin texture. On darker skin tones, redness may not be visible—instead, look for purple or blue discolouration, warmth, or hardness.

The blanching test: Press a finger on any red area. If it goes white (blanches) and then returns to red, blood flow is intact. If it stays red (non-blanching), tissue damage has occurred—contact your GP or tissue viability nurse immediately.

Remember: No cushion eliminates the need for movement. NHS guidelines recommend position changes at least every four to six hours for at-risk users. If you're able, perform "pressure relief lifts" (pushing up on your armrests to lift your bottom off the seat) or lean forward and side-to-side every 20-30 minutes. The cushion buys you time; it doesn't provide immunity.

Frequently Asked Questions

Can I use a regular cushion in my wheelchair? 

Household cushions aren't engineered for pressure redistribution and can actually increase pressure at specific points. They compress unevenly, don't address shear forces, and weren't designed for extended seated use. If you're at any pressure risk, a proper wheelchair cushion is essential.

What's the best cushion for a bony bottom? 

Users with low body fat and prominent bones need cushions that allow deep immersion. Air or gel cushions typically work best, as they let the bony prominences sink in whilst supporting surrounding tissue. High-profile air cushions like ROHO are specifically designed for this body type.

Do I need a prescription to buy a high-risk cushion? 

No. In the UK, you can purchase any wheelchair cushion privately without a prescription. However, for high-risk cushions like air systems, professional assessment and training on proper use is strongly recommended. We offer advisory services to help you select appropriately.