 4.2 DETERMINATION OF PMSF-ARM Pmsf can be estimated measuring the venous pressure Pv and the arterial pressure Pa in on limb after rapid vascular occlusion. This estimation assumes Pa and Pv equilibrium following a rapid vascular occlusion as described by Maas et al2. In order to determine stop-flow time or time of arterial venous balance, we will perform a pilot study in 10 patients. We will measure the radial arterial pressure and venous pressure in the same hand and we will then stop the blood-flow during 30 -60 seconds using an automatic pneumatic tourniquet APT pneumatic tourniquet, Anetic Aid, Ltd. Guiseley, UK to pressures 50 mmHg above systolic pressure. Measures will be taken three times in order to assess repeatability. The time required to equilibrate arterial and venous pressure will be the stop-flow time, and will be the time that we need to wait with the tourniquet inflated. In Maas study was between 25 - 30 seconds. 