Understanding the Pressure Injury Prevention Gap

Pressure injury prevention has traditionally relied on two primary strategies: repositioning patients at regular intervals and prescribing support surfaces designed to reduce pressure.

These interventions remain fundamental components of clinical care. However, despite widespread use, pressure injuries continue to develop in some of the most vulnerable patient populations, particularly those who are profoundly immobile and unable to reposition independently.

As our understanding of pressure injury development has evolved, so too has our understanding of the limitations of conventional prevention strategies. While repositioning and alternating air systems address important aspects of tissue loading, they may not fully address every pathway involved in pressure injury formation.

Understanding the strengths and limitations of each approach helps clinicians make more informed decisions when selecting support surfaces for high-risk patients.

The Goal of Pressure Injury Prevention

At its core, pressure injury prevention aims to reduce the amount of time tissue is exposed to harmful loading.

When soft tissue is compressed between a bony prominence and an external surface, several processes begin simultaneously. Blood flow may be reduced, lymphatic drainage can become impaired, and tissues may experience direct mechanical deformation.

The longer these forces remain concentrated in one location, the greater the risk of tissue damage.

Prevention strategies therefore focus on either reducing the magnitude of loading, redistributing loading, or reducing the amount of time tissues are exposed to sustained pressure.

The Role of Repositioning

Repositioning remains one of the oldest and most widely adopted pressure injury prevention strategies.

By changing a patient’s position, loading is redistributed away from vulnerable anatomical areas and blood flow is allowed to recover. Repositioning also helps manage moisture, comfort and respiratory function, making it an important component of holistic patient care.

However, repositioning has several practical limitations.

Firstly, it is labour intensive and dependent on consistent implementation. Secondly, repositioning schedules are generally based on estimated risk rather than individual tissue tolerance. Finally, every repositioning event introduces some degree of movement between the patient and the support surface.

This movement can generate friction and shear forces, particularly in patients who require extensive assistance with transfers and positioning.

For many patients, repositioning remains highly effective. For others, particularly those with severe immobility or compromised tissue tolerance, repositioning alone may not be sufficient.

Understanding Alternating Air Systems

Alternating pressure mattresses were developed to address one of the key limitations of static support surfaces.

Rather than maintaining a constant pressure distribution, alternating air systems cyclically inflate and deflate air cells beneath the patient. This creates periods of loading and unloading across different areas of the body.

The primary benefit of this approach is that it allows intermittent reperfusion of compressed tissues.

In simple terms, areas that were previously under pressure receive periods of relief, helping restore blood flow and reduce the risk of prolonged ischaemia.

This makes alternating air systems an important option for patients at increased risk of pressure injury.

What Alternating Air Systems Do Well

Alternating air systems offer several clinical advantages:

• Regular redistribution of pressure
• Reduced reliance on manual repositioning
• Improved management of prolonged loading
• Support for patients with limited mobility
• Proven use across acute, rehabilitation and aged care settings

For many patients, alternating air systems provide an effective balance between pressure redistribution and practical clinical management.

However, it is important to understand what these systems were originally designed to address.

The Prevention Gap

Alternating air systems primarily target the ischaemic pathway of tissue injury by creating periodic offloading and reperfusion.

What they do not completely eliminate is the presence of sustained loading between cycles.

Even when pressure is redistributed effectively, tissues remain exposed to loading for periods of time before the next cycle occurs. For patients with significantly reduced tissue tolerance, damage may begin to develop before that next offloading phase arrives.

This is particularly relevant when considering direct cell deformation, a mechanism of injury that can occur on a much shorter timeframe than traditional ischaemic damage.

For most patients this may not be clinically significant. For profoundly immobile patients with complex presentations, however, it highlights a potential gap between pressure redistribution and complete management of tissue loading.

The Impact of Shear Forces

Another consideration is shear.

Shear occurs when adjacent tissue layers move in different directions, causing stretching and distortion within the tissue.

Common sources of shear include:

• Sliding down in bed
• Reclined sitting positions
• Transfers
• Manual repositioning

Shear can increase tissue stress and contribute to pressure injury development, particularly when combined with prolonged loading.

Reducing shear is therefore an important consideration when selecting support surfaces and positioning strategies.

What Is Continuous Movement Therapy?

Continuous movement therapy represents a different approach to pressure injury prevention.

Rather than periodically redistributing pressure through alternating cycles, continuous movement systems are designed to maintain slow, uninterrupted changes in patient positioning over extended periods.

The principle is straightforward.

If sustained static loading contributes to tissue damage, continuously changing the loading environment may reduce the amount of time any one anatomical location remains under significant pressure.

Continuous movement systems achieve this through gradual lateral movement that is often imperceptible to the patient.

Unlike traditional manual repositioning, movement occurs slowly and consistently rather than as a series of separate repositioning events.

Potential Clinical Benefits

Continuous movement therapy may offer several theoretical advantages for carefully selected patients.

These include:

• Reduced periods of sustained static loading
• Continuous redistribution of tissue stress
• Reduced dependence on frequent manual repositioning
• Reduced exposure to shear associated with repositioning events
• Improved comfort for patients who find manual repositioning painful

For patients who are profoundly immobile and unable to reposition independently, these benefits may help address aspects of pressure injury prevention that are not fully managed by conventional approaches.

Patient Selection Remains Critical

No support surface is appropriate for every patient.

The effectiveness of any pressure injury prevention strategy depends on the patient’s clinical presentation, mobility, risk profile and care environment.

When selecting a support surface, clinicians should consider:

• Ability to reposition independently
• Existing pressure injuries
• Tissue tolerance
• Sensory impairment
• Weight distribution
• Pain levels
• Care resources available

Support surfaces should be viewed as one component of a broader prevention strategy rather than a replacement for clinical assessment and ongoing care.

Conclusion

Repositioning, alternating air systems and continuous movement therapy all aim to achieve the same outcome: reducing the risk of tissue damage caused by prolonged loading.

Each approach offers distinct advantages and addresses different aspects of pressure injury prevention.

Repositioning remains fundamental to patient care. Alternating air systems provide effective pressure redistribution and support reperfusion. Continuous movement therapy introduces an alternative approach focused on minimising sustained static loading and reducing exposure to prolonged tissue stress.

Understanding the strengths and limitations of each strategy allows clinicians to make more informed decisions and tailor prevention plans to the needs of individual patients.

As pressure injury research continues to evolve, so too will our understanding of how best to protect patients who are most vulnerable to tissue damage.