The aims of this thesis were to study the prevalence, incidence, prevention and treatment of pressure sores, to further develop a risk assessment scale, and test the reliability and validity of this scale, to identify risk factors for pressure sore development, and to study skin blood flow in non-blanchable erythema areas as compared to undamaged skin.

Criteria used for pressure sore assessment were persistent discoloration i.e. non-blanchable erythema, epithelial damage, and damage to the full thickness of the skin either without or with a deep cavity. The prevalence study was based on interviews, with 55 registered nurses, about 1173 patients. A Risk Assessment Pressure Sore scale, i.e. the RAPS scale consisting of twelve variables: general physical condition, activity, mobility, moisture, food intake, fluid intake, sensory perception, :fiiction and shear, skin type, bodily constitution, body temperature and serum albumin, was developed. In total 530 patients were assessed with the RAPS scale within 24 hours of admission, thereafter once a week for a maximum of twelve weeks. To estimate equivalence, 10 pairs of nurses assessed a total of 116 patients. A total of 19 blood flow measurements, in 5 patients were performed, using a Laser Doppler perfusion imager.

The prevalence of pressure sores among 1173 patients was 3.75% and the incidence among 530 patients was 11.75%. The most frequently preventive and treatment measures used were related to pressure relief. After the test of internal consistency, two variables were excluded from the RAPS scale, namely bodily constitution and skin type. The Cronbach's alpha coefficient was 0.83. The factor analyses gave three factors, termed mobility, physical condition and nutrition, with a total variance explained of 65.1%. The intraclass correlation between raters was 0.83. Sensitivity was 75% and specificity 70% among patients on medical wards and corresponding values for patients on infection wards were 80% and 69.7%, respectively. In the multiple logistic regression analyses mobility, length of hospitalisation, age, surgical treatment and weight were identified as risk factors for pressure sore development. The blood flow distribution profiles for areas with non-blanchable erythema and those for undamaged skin were found to be different. As the area of non-blanchable erythema decreased, the blood flow distribution profiles gradually became more homogeneous.

In conclusion, pressure sores are still a problem in nursing care. The RAPS scale is a reliable scale for predicting pressure sore development. The validity is especially good for patients on medical wards and infection wards. The results indicate that the scale may be useful in clinical practice. Mobility is a major risk factor and undergoing surgical treatment increases the risk of developing pressure sores. There are differences between blood flow in areas of non-blanchable erythema as compared to undamaged skin. The skin blood flow seems to increase in relation to the size of the non-blanchable erythema.