Trykksår årsaker. Kunnskap endrer og fornyer seg; men hva hjelper det om ingen tar det i bruk? Årsaker: historisk perspektiv

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1 Trykksår årsaker Forskning har kommet fram til andre årsaks forhold enn de vi er opplært med Kunnskap endrer og fornyer seg; men hva hjelper det om ingen tar det i bruk? Gunnhild Stordalen: Dagens Industri aug. 14 Årsaker: historisk perspektiv I århundre har man ment at O² mangel ødelegger huden Bekreftet på 1930tallet: kapillær kollaps: trykk > 30 mmhg: Kapillærkollaps; O² mangel huden dør, dermed et sår All photo s: Wikipedia 1

2 Historisk perspektiv Forskningens hovedfokus de siste 30+ år: Local ischemia Reperfusion injury Impaired interstitial fluid flow Sustained cell deformity Stekelenburg A, Gawlitta D, Bader DL & Oomens CW (2008): Deep tissue injury: how deep is our understanding? Archives of Physical Medical Rehabilitation 89, Andre årsaksforhold med mer eller mindre relevans: Inkontinens Ernæring Alder Sensibilitet Friksjon Aktivitetsnivå BMI Foto: C Moore Hva er det nye? Bløddeler blir klemt sammen.. I. O² forsyning stopper I. Cellene endrer til anærob II. ( de dør ikke ennå) II. Vevsdeformasjon I. Cellemembran blir trykket sammen og strukket ut (SHEAR STRAIN) II. Osmosen endrer seg III. (cellen ikke glad, men den dør ikke ennå) Etter noen timer Membranforvrenging / vevsdeformasjon (shear strain) Materiale inni cellen blir presset ut i interstitium Enten så dør cellen innen 10 min Eller så dør cellen mellom 2 4 timer Anaerobforsyning Avfallsprodukter kveler cellen Cellen dør etter 2 4 timer (C. Oomens et al 2007) (A. Gefen et al 2009) 2

3 Shear Definisjon Shear Strain Shear forces are the external forces that typically occur at the interface between the person and cushion, parallel to the contact surfaces, however, it is the internal shear deformations and mechanical stresses in the weight-bearing soft tissues that eventually cause cell and tissue death. In fact, even when external shear forces are not apparent or are slight in magnitude, there can still be substantial internal shear loads that occur, even in a symmetrically seated, unmoving posture, as a result of the complex anatomical structures and tissue mechanical property interactions in the living body. Membranforvrengning Loading / deformation treshold Om en belastning (trykket og shear strain) er over et bestemt nivå blir cellemembranen skadet. Denne belastning & celledeformasjon har en direkte forbindelse med «mengde deformasjon» og «tid» Amit Gefen

4 Muscle tissue stress Tolerance of Muscle Tissue to Sustained Deformations: TIME IS A FACTOR HYPOTHESIS: Membrane-Stretch-Induced Cell Death in DTI Immobilization for prolonged periods (minutes to hours, depending on the individual risk) Sustained tissue deformations around bones Individual cells are deformed; membranes are stretched Linder-Ganz et al. Journal of Biomechanics 2006 Does the time-dependence of tolerance relate to cell-level processes? More specifically, does the decrease in tolerance relate to mass transport phenomena in cells? Tissue engineering-based models were used to address these questions Amit Gefin Permeability of membranes and nuclear envelopes increases; diffusivity therefore abnormally increases intra-cellular concentrations of diffusing molecules (e.g. ions, nutrients, waste products) increase beyond homeostatic levels, potentially up to cytotoxic levels Cell death Slomka et al. Cellular and Molecular Bioengineering 2009 Courtesy Amit Gefin S. Loerakker et al 2010: Therefore, to prevent muscle damage that already develops during short periods of mechanical loading, it is important to minimize tissue deformations by means of cushions and mattresses with appropriate stiffness, such that the deformation threshold for damage is not exceeded. If the deformations do exceed the threshold, then the exposure time determines how much damage develops in the tissue. S. Loerakker et al 2010 Limiting the exposure time may therefore also help to minimize the amount of muscle damage due to mechanical loading. In the present study, intermittent load relief appeared to have minimal effect on the damage evolution. 4

5 Stadium I Trykksårkategorier Stadium II Stadium III Stadium IV Aliano et al 2012 Aliano et al 2012 Aliano et al

6 Trykksårkategori I og II ER SÅR Stadium I Stadium II 6