Deep Tissue Injury: How Deep is Our Understanding? Anke Stekelenburg, PhD, Debby Gawlitta, PhD, Dan L. Bader, PhD, Cees W. Oomens, PhD  Archives of Physical Medicine and Rehabilitation  Volume 89, Issue 7, Pages 1410-1413 (July 2008) DOI: 10.1016/j.apmr.2008.01.012 Copyright © 2008 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig 1 Proposed sequence of events during tissue compression. The mechanical properties of the compressed tissues and the geometry will determine the amount of deformation and ischemia experienced. The deformation will start damaging the tissue once Tdef1, the lower deformation threshold, is exceeded. The tissue's cells will start programmed cell death, called apoptosis, eventually resulting in finalized cell death, called (cellular) necrosis. Once the deformation exceeds (Tdef2), the cells will immediately die from necrosis. The induced ischemia will cause the supplies of oxygen and glucose to decrease. The oxygen deprivation will slow down metabolic processes and shift them toward anaerobic metabolism, causing increased lactate production. When the lactate concentration exceeds Tlac or glucose levels fall below Tglu, cell death will be induced, possibly through apoptosis. Archives of Physical Medicine and Rehabilitation 2008 89, 1410-1413DOI: (10.1016/j.apmr.2008.01.012) Copyright © 2008 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig 2 Proposed modifications to the original curve of Reswick and Rogers.25 (A) The original Reswick and Rogers curve with high- and low-risk regions for pressure damage. (B) A graph (solid line) is imposed, representing the damage threshold resulting from ischemia. Before time point i, ischemia will not lead to damage, and below pressure at point ii, blood vessels will not be sufficiently collapsed to cause ischemia. (C) The proposed risk curve due to deformation, ischemia, and other factors. Above external pressure point iii, all time spans will lead to damage. At point iv, the curve follows the Reswick and Rogers curve, and at point v the curve plateaus because at pressures lower than this, no damage will occur. Archives of Physical Medicine and Rehabilitation 2008 89, 1410-1413DOI: (10.1016/j.apmr.2008.01.012) Copyright © 2008 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions

Fig 3 Development of reversible and persistent damage as a function of time and strain. Archives of Physical Medicine and Rehabilitation 2008 89, 1410-1413DOI: (10.1016/j.apmr.2008.01.012) Copyright © 2008 American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation Terms and Conditions