Decubitus (lat. decubare = to lie)

Pressure Ulcer - A pressure ulcer is an area of localised damage to the skin and underlying tissue caused by pressure, shear, friction and or a combination of these.

The above is a working definition. New theories are being developed but further work is required before they can be included in an accepted definition.

Bedsores are accepted to be caused by three different tissue forces:

Pressure or the compression of tissues. In most cases, this compression is caused by the force of bone against a surface, as when a patient remains in a single decubitus position for a lengthy period. After an extended amount of time with decreased tissue perfusion, ischemia occurs and can lead to tissue necrosis if left untreated in an immunocompromised patient.

Shear force, or a force created when the skin of a patient stays in one place as the deep fascia and skeletal muscle slide down with gravity. This can also cause the pinching off of blood vessels which may lead to ischemia and tissue necrosis.

Friction or a force resisting the shearing of skin, may cause excess shedding through layers of the epidermis.

Aggravating the situation may be other conditions such as excess moisture from incontinence, perspiration or exudate. Over time, this excess moisture may cause the bonds between epithelial cells to weaken thus resulting in the maceration of the epidermis. Other factors in the development of bedsores include age, nutrition, vascular disease, diabetes mellitus, and smoking amongst others.

There are currently two major theories about the development of pressure ulcers. The first and most accepted is the deep tissue injury theory which claims that the ulcers begin at the deepest level, around the bone, and move outward until they reach the epidermis. The second less popular theory, is the top-to-bottom model which says that skin first begins to deteriorate at the surface and then proceeds inward

Principally, a decubitus can develop at any place on the body. However, pressure sores do not develop with the same frequency in all body regions subjected to increased pressure. This is due to the fact that the subcutaneous fatty tissue is able to distribute pressure over a greater area, thus weakening the pressure effect. A fatty deposit about 1" thick can reduce the pressure effect by about 50%. While places on the body, where the skin is in close proximity or right up against a bone, are especially at risk of suffering a decubitus. These regions only tolerate about 10% of the pressure that affects other areas without any problems.

Aside from the primary causes of skin damage, secondary risk factors must be considered, which promote the development of a decubitus. These are divided into endogenous and exogenous factors, or risk factors. Which either find their cause with the patient themself, or else in their environment. Some risk factors are outlined as follows:

Age
A patient's age is of great significance when determining the degree of risk of contracting decubitus. In case the patient is elderly, the following points must be taken into consideration:

-	When people age, the structure of their skin changes, making it more susceptible to injuries.
-	Older people usually suffer from basic diseases, which may negatively affect the risk of contracting decubitus.
-	In general, at this point the patient suffers from a reduced state of general health.
-	Very often, mobility is reduced due to old age.
-	This group of people generally do not drink enough fluids, and are often dehydrated.

Exsiccosis (from lat. siccus - dry)
Patients in a reduced general condition often drink too little. The deficit in fluids effects the drying of the skin. Aside from this effect, such an exsiccosis leads to changes in mental abilities. These patients are mentally diminished and articulate themselves in a unusual manner. Different factors contribute to this phenomenon. First of all, when a person ages, the sense of thirst diminishes, i.e. an older person does not notice when he has a fluid deficit. Also, at a more advanced age, the kidneys are mostly active during the night, explaining the general need to urinate more frequently at night. Of course, this fact is perceived as annoying and the intake of fluids is further reduced. Moreover, incontinence also increases the desire to drink less. Without the knowledge of these connections, an older person often reduces himself to a nearly fatal condition of fluid deficit

Reduced Mobility
Reduced mobility is defined as a reduction in maneuverability due to an illness. It represents one of the, if not the most important risk factor for the development of a pressure sore. Due to greatly reduced mobility, a patient often has only a limited possibility, if any, to change position when sitting or lying down. They are not able to counter the pressure to certain regions of their body with pressure relief. Additionally, aside from the effects of immobility. Other problems arise such as badly ventilated lungs, slow digestion, stiffening of the joints, reduction of the muscles of the skeleton, etc. But a patient's psyche is also greatly impaired by immobility. Such patients tend to suffer from depression, in turn promoting and reinforcing the immobility.

Weight
Both very thin as well as very heavy (obese) patients have a greater tendency towards developing a decubitus, than people of normal weight. Due to anatomical and physical circumstances, high pressure affects the endangered parts of the body.

Metabolic and Neurological Diseases
Adverse effects and complications of existing diseases such as diabetes (diabetes mellitus), or stroke (apoplexy), promote the development of a pressure sore. Long-term consequences of diabetes mellitus are neural diseases (neuropathies), vascular diseases (diabetic macro and micro angiopathies), pathologic changes in the kidneys (nephropathies), and changes of the ocular fundus (retinopathies).

The neuropathies often lead to a reduced pain sensation, which means that a patient cannot sense pain arising from pressure to a particular portion of the body. Therefore, no movements on the part of the patient occur to relieve the pressure.

Diabetic macro and micro angiopathies lead to a reduced blood circulation. When blood vessels which are already burdened by pre-existing lack of circulation, are even further compressed by an external source, death of the afflicted cells is virtually unavoidable. But also wound healing of already existing pressure sores is an extremely tedious and complicated process due to the bad supply of blood.

Symptoms of a stroke appropriate to its etiology (origin), may include paresthesia or paralysis. The paresthesia leads to a defective conduction leading to a reduced sensation, if any at all, of pressure. The one-sided paralyses (pareses) significantly reduces the patient's mobility. Often, the affected parts of the body are negated, i.e. the patient does not see the affected half of their body as belonging to them anymore. Here also, there is a significantly increased risk for decubitus due to the pre-existing illness.

Paresthesia
Paresthesia is the complete lack of, reduction or increase of a stimulus. These stimuli include for example; temperature sensation, the perception of being touched, as well as pain. Paresthesia may lead to the patient's being unable to react to pain resulting from pressure by changing position.

Malnutrition
Malnutrition leads to a reduced state of general health, weariness, abnormal fatigue, and weakness. Thus ultimately promoting a patient's immobility. With already existing decubitus, it also delays the process of wound healing.

Incontinence
Incontinence is the inability to excrete urine or feces in a controlled manner. Even though a patient in such a situation is provided with incontinence articles, such as for example diapers. Feces, urine, and bacteria continuously irritate the skin, ultimately resulting in skin damage.

Infections
Infections affect the metabolism negatively and weaken the body's own immune defenses, and therefore also the patient's general state of health. Additionally, patients with infections develop a fever. Which in turn, leads to an increased secretion of sweat. The associated moisture macerates the skin, reducing its resistance against diseases.

the risk of developing a decubitus is assessed according to an evaluation process developed in the USA, which is recognized and applied worldwide. The Braden-scale, named after Prof. Dr. Barbara J. Braden is an instrument recommended in clinical practice to assess the risk of decubitus. (Prof. Dr. Braden is Dean of the Graduate School and the University Colleges of Nursing at the Creighton University in Omaha, Nebraska).

The following risk factors are evaluated in a point-summation process:

The calculated sum then shows a low, medium or high risk of contracting decubitus.

Additionally, a patient's individual circumstances must be taken into consideration. > Evaluation-Sheet (available in german only!!!)