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Heel-skin microvascular blood perfusion responses to sustained pressure loading and unloading
1Nova Southeastern University, College of Medical Sciences, Department of Physiology, Fort Lauderdale, FL 33328, USA.
Objective:
Sustained heel pressure during surgery and during acute and long-term care residence can cause heel blood flow deprivation sufficient to cause pressure ulcers. Because little is known about the amount and distribution of heel blood perfusion changes under these conditions, the aim of this study was to characterize the main features of these changes.
Methods:
Heel blood perfusion by laser Doppler imaging (LDI, 40 x 40 mm scans) was measured in 11 vascularly normal persons before (10 minutes), during heel loading (40 minutes) and after off-loading (20 minutes). Loading was done with subjects supine and one heel on a transparent plate through which LDI data were obtained during loading. Analyses were on progressively increasing areas around the central compression site using 10 x 10, 20 x 20, 30 x 30, and 40 x 40 mm assay areas at each of multiple time points during the 70-minute test.
Results:
(1) Heel perfusion is rapidly and significantly reduced on loading (P < 0.01) with the greatest reduction within the central heel area; (2) perfusion remains uniformly depressed throughout the loading interval; (3) off-loading is associated with a rapid onset, specially heterogeneous hyperemia which exceeds baseline (P < 0.01) for 10 minutes.
Conclusions:
The present seminal findings may serve as a guide to develop sorely needed microvascular tests to help classify heel breakdown risk on a patient-by-patient basis.