Use of high-resolution, high-frequency diagnostic ultrasound to investigate the pathogenesis of pressure ulcer development.

OBJECTIVES: To investigate the pathogenesis of pressure ulcers utilizing high-resolution ultrasound and to explore the utility of this technology for the detection of incipient pressure ulcers prior to visual clinical signs.
DESIGN: An observational prospective study comparing high-resolution ultrasound images obtained from 119 long-term-care facility residents determined to be at risk for pressure ulcer development (Braden Scale score of 18 or less) with images obtained from 15 healthy volunteers (medical students and medical residents). Common pressure ulcer sites were scanned, including the heels, sacrum, and ischial tuberosity.
SETTING: A medical center and a long-term-care facility. INTERVENTION: Anatomic sites universally accepted as at risk for pressure ulcer development were scanned using high-resolution ultrasound; the sites did not have visual evidence of skin breakdown. The images obtained from the long-term-care facility residents were compared with images considered normal that were obtained from healthy volunteers. In addition, documentation of the clinical assessment finding for erythema was reviewed, recorded, and compared with the high-resolution ultrasound finding for each specific site. MEASUREMENTS: The images obtained were classified as not readable, normal, or abnormal. The images classified as abnormal were further classified by depth of abnormal finding: pattern 1 (deep) or pattern 2 (superficial). The images classified with the abnormal finding pattern 1 (deep) were further classified and subdivided by anatomic location of abnormal finding(s): subgroup 1, abnormal findings in the subdermal area only; subgroup 2, subdermal and dermal abnormal findings; and subgroup 3, subdermal, dermal, and subepidermal edema. Pattern 2 (superficial) included images with abnormal findings limited to the dermal/epidermal junction.
RESULTS: 630 (55.3%) of the images obtained from the long-term-care residents were different from the images obtained from the healthy volunteers. The healthy volunteers' images classified as normal had the expected ultrasound findings for homogeneous pattern of ultrasound reflections, allowing for visualization of various skin layers (epidermis, superficial papillary dermis, deep reticular dermis, and hypodermis) and subcutaneous tissue (subdermal). However, many images (55.3%) obtained from the residents at risk for pressure ulcer development had patterns where areas within the various skin layers were not visible, interrupted by areas indicative of fluid or edema. Moreover, most images (79.7%) with abnormal ultrasound patterns did not have documentation of erythema.
CONCLUSION: High-resolution ultrasound is an effective tool for the investigation of skin and soft tissue changes consistent with the documented pathogenesis of pressure ulcers. A progressive process for pressure ulcer development from deep subdermal layers to superficial dermal then epidermal layers can be inferred. Dermal edema was only present with subdermal edema. In other words, there was never evidence of dermal edema in the absence of subdermal edema. A better understanding of the pathogenesis of pressure ulcers through the use of high-resolution ultrasound to detect soft tissue damage and edema before visible clinical signs could lead to earlier and more focused pressure ulcer prevention programs, resulting in reduced pain and suffering for improved patient quality of life and wound care cost savings.