Biophysical characteristics of medical compression stockings

Summary Aim: Haemodynamic effectivity of 13 compression stockings in correlation with its physical characteristics. Patients, methods: In a prospective study, 42 patients in clinical stage C1–4 were examined with dynamic mercury strain gauge plethysmography to determine the effects of 13 different compression stockings in compression classes 2 and 3 (CEN) on venous haemodynamics. At the same time that venous function measurement was monitored, the pressure exerted by the compression stockings was measured under resting conditions and during standardized exercises by the patients. Results: Resting pressure measured while the patient was reclining corresponded to the in vitro textile data for the corresponding compression class in all of the stockings. The compression stockings improved venous refill times t0 and t1/2 to a statistically significant degree. The differences in the improvement in refill times t0 and t1/2 was found to depend on the quotient of maximum working pressure during movement over resting pressure (pW/pR) while standing (r = 0.90, p < 0.01 ). The improvement of the expelled volume correlated with decrease of resting pressure from ankle to calf (r = 0.86, p <0.01 ). Conclusion: Compression stockings that exert the same resting pressure at ankle level in reclining patients can still have different effects on venous haemodynamics. The haemodynamic effectivity of the various compression materials is determined above all by the degree of stiffness, which can be characterized in vivo as the ratio of maximum working pressure to resting pressure (pW/pR) while standing.

Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest

Louisy, Francis, Philippe Schroiff, and Antonio Güell.Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest. J. Appl. Physiol. 82(6): 1726–1733, 1997.—Leg venous hemodynamics [venous distensibility index (VDI), arterial flow index (AFI), half-emptying time (T1/2)], and leg volumes (LV) were assessed by mercury strain-gauge plethysmography with venous occlusion and volometry, respectively, in seven men before, during, and after 42 days of 6° head-down bed rest. Results showed a high increase in VDI up to day 26 of bed rest (+50% vs. control at day 26, P < 0.05), which tended to subside thereafter (+20% increase vs. control value at day 41, P < 0.05). VDI changes were associated with parallel changes in T1/2 (+54% vs. control at day 26 of bed rest, P < 0.05, and +25% vs. control at day 41, P < 0.05) and with a decrease in AFI (−49% at day 41 vs. control, P < 0.05). LV continuously decreased throughout bed rest (−13% vs. control at day 41, P < 0.05) but was correlated with VDI only during the first month of bed rest. These results show that during long-term 6° head-down bed rest alterations of leg venous compliance are associated with impairment of venous emptying capacities and arterial flow. Changes in skeletal muscle mass and fluid shifts may account for venous changes during the first month of bed rest but, subsequently, other physiological factors, to be determined, may also be involved in leg venous hemodynamic alterations.

D-Dimers, Thrombin Antithrombin III Complexes and Prothrombin Fragments 1 + 2: Diagnostic value in Clinically Suspected Deep Vein Thrombosis

SummaryThis study was performed to determine the accuracy of D-Dimer fibrin derivatives, thrombin-antithrombin III (TAT) complexes and prothrombin fragments 1 + 2 (F 1 + 2) determinations for the diagnosis of deep vein thrombosis (DVT). One hundred and sixteen consecutive patients referred to the angiology unit of our hospital for a clinically suspected DVT were investigated. They were submitted to mercury strain gauge plethysmography and to ultrasonic duplex scanning examination; in cases of inconclusive results or of proximal DVT (n = 35), an ascending phlebography was performed. After these investigations were completed, the diagnosis of DVT was confirmed in 34 and excluded in 82. One half of the patients were already under anticoagulant therapy at the time of investigation. The 3 biological markers were assayed using commercially available ELISA techniques and the D-Dimer was also assayed with a fast latex method. The normal distribution of these markers was established in 40 healthy blood donors. The most accurate assay for the diagnosis of DVT was the D-Dimer ELISA which had both a high sensitivity (94%) and a high negative predictive value (95%). The D-Dirner latex, TAT complexes and F 1 + 2 were far less sensitive and provided negative predictive values which ranged between 78 and 85%. In spite of positive and significant correlations between the levels of ihe 3 markers, their association did not improve their overall accuracy for detecting D\/L Therefore, with the exception of the D-Dimer ELISA, these markers were of little value for the diagnosis of DVT in this specific population.

Mercury Strain-Gauge Plethysmography Venous Mode: Non-Invasive Technique of Choice in Vascular Pathology

Mercury strain-gauge plethysmography venous mode is a non-invasive technique for exploration of the haemodynamics of the extremities. The plethysmographic parameters used are: (1) the venous inflow (in ml/100 ml/min); (2) the venous outflow (in ml/100 ml/min); (3) the venous capacity in ml/100ml; (4) the venous distensibility index in ml/100 ml/ mmHg; and (5) the venous pressure measured by ‘hysteresis curve’. This method permits us to analyse the venous haemodynamics of both extremities simultaneously (the normal limb serving as the control), to obtain a precise diagnosis and to appreciate the efficacy of treatment at follow-up. The aetiology of the swollen limb can be precisely identified in 95% of the studied cases: oedema in superficial venous insufficiency, oedema in the deep venous insufficiency, oedema of inflammatory origin, oedema in the arterial insufficiency, oedema of cardiac origin, lymphoedema. During the last 3 years, we have followed up 580 patients with this method.