Heel response to external pressure: Is it the same in healthy community-dwelling adults and in hip surgery patients?

Abstract

PURPOSE: The purpose of the study was to determine whether the interface pressure created when the heel is in contact with the bed surface reduced healthy adults' heel oxygen delivery (transcutaneous oxygen [TcO2]) and raised heel skin temperature. We also determined whether there was a hyperemic response to pressure relief on 3 consecutive days, and compared data from healthy adults to that from hip surgery patients. DESIGN: A 1-group, prospective, repeated-measures design guided data collection and analysis. SUBJECTS AND SETTINGS: Eighteen subjects were age (±5 years) and gender-matched with a previous study on hip surgery patients. The mean age of study participants was 57.3 ± 15.75 (mean ± SD) years and half were men (n = 9). METHODS: Oxygen and temperature sensors were placed on the plantar surface of each foot, close to the heels. Measures were taken when the heels were (1) suspended above the bed surface (preload), (2) on the bed surface for 15 minutes (loading), and (3) again suspended above the bed surface for 15 minutes (unloading). Repeated measures analysis of variance was used to analyze the data. RESULTS: When compared with preload, both loading and unloading on all 3 days resulted in a statistically significant bilateral reduction in heel TcO2 (P < .001) and a bilateral increase in heel skin temperature (P = .001). There was a significant bilateral heel hyperemic response (during the first 3 minutes of immediate heel unloading) on all 3 days. There were significant changes in heel TcO2 (P = .008) and heel skin temperature (P < .001) in both legs when pressure was relieved. The hyperemic response was not apparent in the operative leg in our prior hip surgery group. When comparing one of the legs of the healthy adults with the operative leg of the prior hip surgery patients, heel TcO2 in both groups decreased (P < .001) while heel skin temperature increased during both loading and unloading in all 3 days (P < .001). CONCLUSION: Heel TcO2 fell while heel skin temperature increased with both the application and removal of external pressure in healthy adults. The fall in TcO2 and the rise in heel skin temperature were also apparent in the operative leg of the hip surgery group. The brief period of hyperemia, measured by abrupt changes in heel TcO2 and heel skin temperature, was present only in healthy subjects. This raises the question of whether heel pressure ulcer development is related to a blunted hyperemic response in subjects with hip surgery. Further studies are needed that explore the effects of varying the duration of pressure on the hyperemic response as a strategy to understand heel pressure ulcer prevention. Since heel TcO2 fell in both groups after a brief pressure application of 15 minutes, nurses should keep heels off-load at all times to ensure adequate heel skin oxygenation.