Compression therapy with stockings or bandages is the most common treatment for venous or lymphatic disorders. The objective of this study was to investigate the influence of bandage mechanical properties, application technique and subject morphology on the interface pressure, which is the key of this treatment. Bandage stretch and interface pressure measurements (between the bandage and the leg) were performed on 30 healthy subjects (15 men and 15 women) at two different heights on the lower leg and in two positions (supine and standing). Two bandages were applied with two application techniques by a single operator. The statistical analysis of the results revealed: no significant difference in pressure between men and women, except for the pressure variation between supine and standing positions; a very strong correlation between pressure and bandage mechanical properties (p < 0.00001) and between pressure and bandage overlapping (p < 0.00001); a significant pressure increase from supine to standing positions (p < 0.0001). Also, it showed that pressure tended to decrease when leg circumference increased. Overall, pressure applied by elastic compression bandages varies with subject morphology, bandage mechanical properties and application technique. A better knowledge of the impact of these parameters on the applied pressure may lead to a more effective treatment.

Abstract

Left ventricular assist device (LVAD) use has continued to grow. Despite recent advances in technology, LVAD patients continue to suffer from devastating complications, including stroke and device thrombosis. Among several variables affecting thrombogenicity, we hypothesize that insertion depth of the inflow cannula into the left ventricle (LV) influences hemodynamics and thrombosis risk. Blood flow patterns were studied in a patient-derived computational model of the LV, mitral valve (MV), and LVAD inflow cannula using unsteady computational fluid dynamics (CFD). Hundreds of thousands of platelets were tracked individually, for two inflow cannula insertion depth configurations (12 mm—reduced and 27 mm—conventional) using platelet-level (Lagrangian) metrics to quantify thrombogenicity. Particularly in patients with small LV dimensions, the deeper inflow cannula insertion resulted in much higher platelet shear stress histories (SH), consistent with markedly abnormal intraventricular hemodynamics. A larger proportion of platelets in this deeper insertion configuration was found to linger in the domain for long residence times (RT) and also accumulated much higher SH. The reduced inflow depth configuration promoted LV washout and reduced platelet SH. The increase of both SH and RT in the LV demonstrates the impact of inflow cannula depth on platelet activation and increased stroke risk in these patients. Inflow cannula depth of insertion should be considered as an opportunity to optimize surgical planning of LVAD therapy.

Abstract