Pressure Ulcers

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DEFINITION

The National Pressure Ulcer Advisory Panel,U.S (NPUAP) defines a pressure ulcer as an area of unrelieved pressure over a defined area, usually over a bony prominence, resulting in ischemia, cell death, and tissue necrosis.

The terms decubitus ulcer (from Latin decumbere, “to lie down”), pressure sore, and pressure ulcer often are used interchangeably

PATHOPHYSIOLOGY

In 1873, Sir James Paget described the production of pressure ulcers remarkably well, and his description is still quite accurate today.

Many factors contribute to the development of pressure ulcers, but pressure leading to ischemia and necrosis is the final common pathway.

Pressure ulcers result from constant pressure sufficient to impair local blood flow to soft tissue for an extended period. This external pressure must be greater than the arterial capillary pressure (32 mm Hg) to impair inflow and greater than the venous capillary closing pressure (8-12 mm Hg) to impede the return of flow for an extended time.Tissues are capable withstanding enormous pressures for brief periods, but prolonged exposure to pressures just slightly above capillary filling pressure initiates a downward spiral toward tissue necrosis and ulceration. The superficial dermis can tolerate ischemia for 2 to 8 hours before breakdown occurs. Deeper muscle, connective, and fat tissues tolerate pressures for 2 hours or less(probably because of its increased need for oxygen and higher metabolic requirements). Thus, there may be significant damage to underlying tissues while the epidermis and dermis remain intact.By the time ulceration is present through the skin level, significant damage of underlying muscle may already have occurred, making the overall shape of the ulcer an inverted cone.

Other factors contributing to pressure ulcers include-

• Friction

Friction is the resistance to motion. It may occur when the skin is dragged across a surface, such as when you change position or a care provider moves you. The friction may be even greater if the skin is moist. Friction may make fragile skin more vulnerable to injury.

• Shear

Shear occurs when two surfaces move in the opposite direction. For example, when a hospital bed is elevated at the head, you can slide down in bed. As the tailbone moves down, the skin over the bone may stay in place — essentially pulling in the opposite direction. This motion may injure tissue and blood vessels, making the site more vulnerable to damage from sustained pressure.

 SITES

The areas most susceptiblle to pressure in recumbent position include:

• SUPINE : 

1. Occiput
2. Scapulae
3. Vertebrae
4. Elbows
5. Sacrum
6. Coccyx
7. Heels

• PRONE :

1. Ears (head rotated)
2. Shoulders (anterior aspect)
3. Illiac crest
4. Male genital region
5. Patella
6. Dorsum of feet  

• SIDE-LYING -   

1. Scapulae
2. Vertebrae
3. Elbows
4. Sacrum
5. Coccyx
6. Heels
7. Ears
8. Shoulders (lateral aspect)
9. Greater trochanter
10. Head of fibula
11. Knees (medial aspect from contact between knees)
12. Lateral malleolus
13. Medial malleolus (contact between malleoli)

RISK FACTORS

People are at risk of developing pressure sores if they have difficulty moving and are unable to easily change position while seated or in bed. Immobility may be due to:

• Generally poor health or weakness
• Paralysis
• Injury or illness that requires bed rest or wheelchair use
• Recovery after surgery
• Sedation
• Coma

Other factors that increase the risk of pressure sores include:

• Age. The skin of older adults is generally more fragile, thinner, less elastic and drier than the skin of younger adults. Also, older adults usually produce new skin cells more slowly. These factors make skin vulnerable to damage.
• Lack of sensory perception. Spinal cord injuries, neurological disorders and other conditions can result in a loss of sensation. An inability to feel pain or discomfort can result in not being aware of bedsores or the need to change position.
• Weight loss. Weight loss is common during prolonged illnesses, and muscle atrophy and wasting are common in people with paralysis. The loss of fat and muscle results in less cushioning between bones and a bed or a wheelchair.
• Poor nutrition and hydration. People need enough fluids, calories, protein, vitamins and minerals in their daily diet to maintain healthy skin and prevent the breakdown of tissues.
• Excess moisture or dryness. Skin that is moist from sweat or lack of bladder control is more likely to be injured and increases the friction between the skin and clothing or bedding. Very dry skin increases friction as well.
• Bowel incontinence. Bacteria from fecal matter can cause serious local infections and lead to life-threatening infections affecting the whole body.
• Medical conditions affecting blood flow. Health problems that can affect blood flow, such as diabetes and vascular disease, increase the risk of tissue damage.
• Smoking. Smoking reduces blood flow and limits the amount of oxygen in the blood. Smokers tend to develop more-severe wounds, and their wounds heal more slowly.
• Limited alertness. People whose mental awareness is lessened by disease, trauma or medications may be unable to take the actions needed to prevent or care for pressure sores.
• Muscle spasms. People who have frequent muscle spasms or other involuntary muscle movement may be at increased risk of pressure sores from frequent friction and shearing.
  

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