Features of lymphatic dysfunction in compressed skin tissues – Implications in pressure ulcer aetiology

Abstract

ObjectiveImpaired lymph formation and clearance has previously been proposed as a contributory factor in the development of pressure ulcers. The present study has been designed to trial fluorescence lymphangiography for establishing how lymphatic function is altered under a clinically relevant form of mechanical loading. MethodsLymph formation and clearance was traced in both forearms by an intradermal injection of indocyanine green (ICG)(50µl, 0.05%w/v), imaged using a commercial near-infrared fluorescence imaging unit (Fluobeam® 800). External uniaxial loading equivalent to a pressure of 60mmHg was applied for 45 minutes in one arm using a custom-built indenter. ResultsLoading was associated with a decreased frequency of normal directional drainage (DD) of ICG within delineated vessels, both immediately after loading and 45 minutes thereafter. Loading was also associated with non-directional dispersal (NDD) of ICG within the interstitium. Signal intensity within NDD was often greatest at areas of stress concentration, producing a 'halo pattern', corresponding to the rounded edges of the indenter. ConclusionsThese results suggest that loading skin with a clinically relevant magnitude of pressure alters both lymph formation and clearance. Further work to quantify impaired clearance under mechanical loading could provide valuable insight into their involvement in the development of pressure ulcers.

Monitoring contractile dermal lymphatic activity following uniaxial mechanical loading

“…Based on the recent study by the authors which involved qualitative assessment of loaded human lymphatic vessels [11] , the present work derives a series of robust quantitative parameters to define lymphatic function both prior to and following the application of uniaxial mechanical loading. A sensitivity analysis was performed to verify the image processing techniques which were used to define transient lymphatic activity.…”

“…They were requested to remain as still as possible for the duration of the study, to minimize the contribution of passive mechanisms to lymphatic clearance and reduce the impact of movement artefact during NIR imaging. Indocyanine green (ICG) injections of 50 μL 0.05% w/v at a shallow intradermal depth were administrated to delineate dermal vessels [11] . Single injections were delivered into the two inter-digital spaces between the thumb and the second finger by a registered nurse (DV), constituting a total micro-dose of 0.05 mg. To encourage rapid uptake of ICG into lymphatic vessels, participants were instructed to clench their fists 20 times following injection.…”

“…A specially designed indenter, with nominal diameter of 42.5 mm and curved edges to minimise stress concentrations, was mounted on a cantilever beam with an incorporated load cell [11] . A load was prescribed equivalent to a pressure of 60 mmHg (8 kPa), for a period of 40 mins ( Fig.…”

“…To date, related research on humans has been restricted to subjective measures of lymph flow using lymphography techniques with cuffs or restrictive collars [10] . The authors of the present study have recently adopted a minimally invasive approach, using Indocyanine green (ICG) fluorescence imaged with an NIR camera, to qualitatively describe the effects of applied uniaxial loading on lymph vessel patency [11] . However, there is a need to provide objective quantification of lymphatic vessel function before and after mechanical loading to provide a basis for reliable clinical translation.…”

Biotribology of the ageing skin—Why we should care

“…Pressure ulcers are related to compression-induced ischaemia (i.e. reduction up to blocking of blood flow), and also, reperfusion of capillary blood flow when load is removed [166,167]. Ischaemia disrupts nutrient supply and promotes the accumulation of waste products and build-up of acidity [167], which ultimately compromise tissue integrity.…”