NO-mediated Vascular Function in Covid-19 Patient

"The investigation consists of a non-invasive evaluation by ultrasounds performed on the common femoral artery investigating the speed of arterial blood flow \[Leg Blood Flow LBF\] and diameter of vessel with a dedicated ultrasound system (General Electric Medical Systems, Milwaukee, WI) using Doppler method, before and after a passive flexion-extension movement of the knee. A linear probe will be used with a frequency of 5 MHz. Using the diameter of the artery and the average volume (Vmean), the LBF will be calculated every second with the formula=Average volume\*PiGreco\*(vessel diameter / 2)2\*60.~The subject will be placed in a sitting position for 20 minutes before the test. The protocol consists of image acquisition for 60 seconds (basal measurement), followed by a passive flexion-extension of the knee (single passive leg movement). The knee flexion will be performed by health care personnel at a rate of 1 Hz. At the end of the movement, the recording will continue for 60 seconds."