Etiologic factors in pressure sores: an experimental model

Area of Science:

• Biomedical Engineering
• Tissue Mechanics
• Wound Healing Research

Background:

• The established threshold for pressure-induced ischemia leading to pressure sores is 35mmHg for 2 hours.
• Clinical observations suggest skin can tolerate normothermic ischemia for 8-12 hours without necrosis.
• Existing experimental models for pressure sore development lack clinical relevance.

Purpose of the Study:

• To design and utilize a novel electromechanical pressure applicator for reproducible pressure sore induction.
• To investigate the pressure-duration thresholds for tissue damage in normal and paraplegic swine.
• To challenge and refine the understanding of pressure-induced ischemia in pressure sore etiology.

Main Methods:

• Development of a computer-controlled electromechanical pressure applicator for continuous monitoring.
• Application of controlled pressure over the greater femoral trochanter in normal and paraplegic swine.
• Histopathological examination of tissue damage at the pressure site after 1 week.

Main Results:

• Three distinct groups of lesions were observed: muscle damage only, muscle and deep dermis damage, and full-thickness damage.
• A critical pressure-duration curve for pressure sore development in normal swine was established.
• Skin integrity was maintained at 200mmHg for 15 hours, contradicting the 35mmHg for 2 hours threshold.

Conclusions:

• Muscle tissue is more susceptible to pressure-induced damage than skin, with initial pathology occurring in muscle.
• The pressure-duration threshold for pressure sore development is significantly higher than previously stated for normal tissue.
• Paraplegia, infection, or repeated trauma may dramatically lower the pressure-duration threshold, increasing susceptibility to pressure sores.