Bedsores, also known as pressure ulcers or decubitus ulcers, are localized injuries to the skin and underlying tissue, typically over bony prominences. The primary factors leading to their development are mechanical forces that impede blood flow, but several underlying health and environmental conditions contribute significantly to a person's risk. Preventing these wounds requires a thorough understanding of their root causes and proactive management.
The Primary Culprits: Pressure, Friction, and Shear
These three mechanical forces are the most direct and significant causes of bedsores. While they often occur in combination, each factor plays a distinct role in damaging the skin.
Prolonged Pressure
Constant, unrelieved pressure on any part of the body is the leading cause of bedsores. When a person remains in one position for too long—such as sitting in a wheelchair or lying in bed—the weight of their body compresses the soft tissue against a hard surface. This compression pinches and restricts the blood vessels, cutting off the supply of oxygen and essential nutrients to the skin and underlying tissues. Without this nourishment, the tissue begins to break down and die, leading to the formation of an ulcer. The areas most at risk are those where bone is close to the skin's surface, as there is less padding to cushion the pressure.
Friction
Friction is the force created when skin rubs against another surface, like bedding, clothing, or a medical device. This repeated rubbing can wear away the top layers of the skin, making it more fragile and vulnerable to injury. This risk is particularly high when the skin is moist, as the combination of moisture and friction can cause the skin to macerate and tear easily. A common example is a patient being pulled across sheets during repositioning instead of being properly lifted.
Shear Forces
Shear damage occurs when two surfaces move in opposite directions, causing blood vessels and deeper tissues to stretch and tear. A classic example is when a person in an inclined bed slides down toward the foot of the bed. The skin over the tailbone may remain in place, while the underlying bone and tissue slide, creating a tearing force. This internal damage can be very severe and is often not visible on the surface until the wound is well-developed. Shear is a frequent contributor to bedsores, especially on the sacrum.
Underlying Risk Factors That Increase Vulnerability
Beyond the primary mechanical forces, several other factors contribute to a person's susceptibility to bedsores. Managing these conditions is crucial for effective prevention.
Limited Mobility and Immobility
Individuals who are unable to change positions on their own are at the highest risk. This can be due to paralysis, illness, sedation, or post-surgery recovery. For these individuals, consistent repositioning by a caregiver is essential to relieve pressure on vulnerable areas.
Moisture and Incontinence
Extended exposure to moisture from sweat, urine, or feces can soften the skin, making it more prone to friction and breakdown. The enzymes and bacteria in urine and feces are also highly damaging to the skin. Proper hygiene, moisture barriers, and frequent checking and changing of soiled linens are key preventive measures.
Poor Nutrition and Dehydration
A person's diet plays a vital role in skin health and tissue repair. Inadequate intake of fluids, protein, calories, vitamins, and minerals weakens the skin's integrity and impairs the body's ability to heal existing wounds. Malnourished individuals, or those who are very thin, also lack the fatty tissue necessary to cushion bony areas.
Reduced Sensory Perception
Conditions that cause a loss of sensation, such as spinal cord injuries, nerve damage (neuropathy), or dementia, can prevent a person from feeling pain or discomfort. This means they may not be aware of the warning signs that indicate tissue damage is occurring and won't feel the need to shift their weight, leaving them in a high-risk position for extended periods.
Age-Related Changes
With advanced age, skin becomes thinner, more fragile, and less elastic. Reduced circulation and underlying health conditions common in older adults, such as diabetes and heart failure, further increase the risk of bedsores by affecting blood flow and the body's healing capacity.
Common Pressure Points: Where Bedsores Develop
Bedsores can form anywhere pressure is applied, but they are most common over bony areas of the body. For bedridden individuals, these areas include:
- The tailbone (sacrum) and buttocks
- The shoulder blades and spine
- The back of the head or ears
- The hips and elbows
- The heels and ankles
For wheelchair users, common sites include:
- The tailbone and buttocks
- The shoulder blades
- The back of the arms and legs that rest against the chair
A Comparison of Pressure vs. Friction vs. Shear Injuries
| Feature | Pressure | Friction | Shear |
|---|---|---|---|
| Primary Cause | Compression of tissue between a bony prominence and a hard surface. | Skin rubbing against another surface. | Opposing forces on the skin and deeper tissue, causing stretching and tearing of blood vessels. |
| Damage Location | Deep tissue injury over bony areas, progresses outward. | Epidermal (top layer) or superficial skin tears and abrasions. | Deeper tissue damage, tearing of blood vessels, with surface skin sometimes appearing intact initially. |
| Appearance | Initially presents as discolored, non-blanchable skin (e.g., persistent redness in light skin, darker patches in darker skin). Can progress to an open wound. | Reddened, chafed, or scraped-looking skin. | Often appears as an undermining wound, where the surface skin is intact but the underlying tissue is separated and damaged. |
| Common Scenario | Lying motionless in bed or sitting in a wheelchair for hours. | Being dragged or pulled across bedsheets during a transfer. | Sliding down in a hospital bed with the head elevated. |
Preventing Bedsores: A Proactive Approach
Prevention is always the best strategy for bedsores. A comprehensive approach involves several key steps.
- Repositioning Regularly: Change the position of an immobile person at least every two hours. Wheelchair users should shift their weight or be repositioned hourly.
- Using Specialized Support Surfaces: Employ pressure-reducing mattresses, overlays, and cushions to distribute weight more evenly and reduce pressure on vulnerable areas.
- Maintaining Good Hygiene: Keep the skin clean and dry. Use mild cleansers and moisturizers. If incontinence is an issue, clean the skin promptly and use a protective skin barrier cream.
- Ensuring Proper Nutrition and Hydration: Provide a balanced diet rich in protein, vitamins, and minerals, along with adequate fluids, to support healthy skin and tissue integrity.
- Performing Daily Skin Checks: Visually inspect the skin, especially over bony prominences, for any early signs of redness, discoloration, or irritation. Early detection is critical for prevention.
Conclusion: The Path to Prevention and Proper Care
Recognizing the key factors that cause bedsores—prolonged pressure, friction, and shear—is fundamental to effective prevention. By addressing these mechanical forces and managing underlying risk factors like immobility, moisture, and poor nutrition, caregivers and patients can significantly reduce the risk of developing these painful wounds. Early detection through regular skin checks and a proactive care plan are essential for maintaining skin health and well-being. For more detailed information on risk factors and prevention strategies, consult authoritative sources like the Mayo Clinic's guide on bedsores.
