Assessment of orthostatic fluid shifts with strain gauge plethysmography

Roland D Thijs (1) , Maaike Bruijnzeels , Adriaan M Kamper , Arjan D van Dijk , J Gert van Dijk

1 Neurology

We evaluated the use of strain gauge plethysmography (SGP) for the assessment of orthostatic fluid shifts during head up tilt (HUT). Subjects wore a parachute harness fixed to the tilt table to avoid muscle tension in the lower limbs during HUT. 22 Healthy subjects (9 women) were tilted for 5 minutes. Calf volume changes as measured by SGP, surface EMG, heart rate and blood pressure were measured continuously. Ten subjects underwent a second tilt test during which circulation in one leg was occluded with a pressure cuff at 250 mmHg. During HUT with occlusion, calf volume increased in the non-occluded leg by 1.9¡Ó0.3% (mean ?b SEM) and 0.2¡Ó0.2% in the occluded leg (p<0.001). During HUT without occlusion a significant correlation (r = 0.9) was found between measurements of the left and right leg with a mean difference of 0.03¡Ó0.1%. HUT did not cause significant changes of surface EMG. A significant gender effect was found: calf volume increased more in men than in women (right leg: 2.9¡Ó0.2% vs. 1.4¡Ó0.2%, p<0.001; left leg: 3.0¡Ó0.2 % vs 1.4¡Ó0.2%; p<0.001). Men were significantly taller, but the hemodynamic response to HUT did not differ significantly between both sexes. SGP during HUT with a parachute harness is a reliable method to assess orthostatic fluid shifts. The gender differences in orthostatic pooling in the calf are best explained by a higher calf compliance in men than in women together with a greater hydrostatic pressure due to a greater height in men.

Mots clés: Medicine

Roland D Thijs, Maaike Bruijnzeels, Adriaan M Kamper, Arjan D van Dijk, J Gert van Dijk. Assessment of orthostatic fluid shifts with strain gauge plethysmography. Clinical Science, 2007, 113 (9), pp.369-374. ⟨10.1042/CS20070060⟩. ⟨hal-00479368⟩