OBJECTIVE: To assess the effects of compression on the skin microcirculation of the heel using laser Doppler fluxmetry. DESIGN: Parallel groups comparing patients with control groups. SETTING: Department of Surgery, University College London Medical School, London. SUBJECTS AND MATERIALS: Ten patients at risk of developing pressure ulceration, 10 age- and sex-matched healthy subjects and 10 young, healthy volunteers. An acrylic indenter with a slot to accommodate a laser Doppler probe was used to apply compression to the heel region. A pressure sensor was used to measure the applied compression. OUTCOME MEASURES: The resting laser Doppler flux was measured with the subject lying supine. Compression forces were then applied in increments from 50 g to 1500 g and the corresponding interface pressure (IP) and laser Doppler flux (LDF) recorded. The IP and LDF were also measured from the heel while the subject was lying on a low air-loss system and then on an NHS conventional hospital bed. RESULTS: The resting LDF is lower in the patient group compared to the control groups (p < 0.05). Compression of the heel caused a progressive decrease in LDF in all groups. Compression greater than 50 mmHg as well as lying on an NHS bed reduced the LDF signal to a minimal value (biological zero). On the low air-loss system, the median LDF was 17% of the resting value in the age-matched control group and 32% in the patient group. CONCLUSIONS: The results indicate that the heel microcirculation is vulnerable to compression. The low air-loss system maintained the IP sufficiently low to prevent complete cessation of the heel microcirculation.
OBJECTIVE: To assess the effects of compression on the skin microcirculation of the heel using laser Doppler fluxmetry. DESIGN: Parallel groups comparing patients with control groups. SETTING: Department of Surgery, University College London Medical School, London. SUBJECTS AND MATERIALS: Ten patients at risk of developing pressure ulceration, 10 age- and sex-matched healthy subjects and 10 young, healthy volunteers. An acrylic indenter with a slot to accommodate a laser Doppler probe was used to apply compression to the heel region. A pressure sensor was used to measure the applied compression. OUTCOME MEASURES: The resting laser Doppler flux was measured with the subject lying supine. Compression forces were then applied in increments from 50 g to 1500 g and the corresponding interface pressure (IP) and laser Doppler flux (LDF) recorded. The IP and LDF were also measured from the heel while the subject was lying on a low air-loss system and then on an NHS conventional hospital bed. RESULTS: The resting LDF is lower in the patient group compared to the control groups (p < 0.05). Compression of the heel caused a progressive decrease in LDF in all groups. Compression greater than 50 mmHg as well as lying on an NHS bed reduced the LDF signal to a minimal value (biological zero). On the low air-loss system, the median LDF was 17% of the resting value in the age-matched control group and 32% in the patient group. CONCLUSIONS: The results indicate that the heel microcirculation is vulnerable to compression. The low air-loss system maintained the IP sufficiently low to prevent complete cessation of the heel microcirculation.