Initial resting measurements were performed as follows:
Femoral artery blood flow. FABF was obtained using
an Esaote Biomedica AU4 Idea Ultrasound Doppler system
(Esoate Biomedica Ltd., Florence, Italy). The femoral artery
insonation site chosen was 1–2 cm distal to the inguinal
crease. Care was given to avoid imaging the femoral artery
too far below the inguinal crease due to arterial branching.
This position was marked on the subject’s skin for ultrasound
head repositioning, thus decreasing the error of site
relocation (17). The muscular wall of the artery and high
blood pressure allowed positioning of the transducer without
deformation of its circular shape (22). The femoral
artery was then imaged with a 10.0-MHz transducer at an
angle as parallel as possible to flow (inherent angle corrections
were made). From the longitudinal image of the femoral
artery (along the central path of the ultrasound beam
where optimal spatial resolution occurs) systolic and diastolic
diameters of the femoral artery were determined to
allow the calculation of an average (systolic [1/3] and diastolic
[2/3]) cross-sectional area (CSA ·r2) (17). Ra¨degran
(17) reported that femoral artery CSA was reproducible
with a mean coefficient of variation of 1.2%, whether the
probe was fixed or repositioned. Doppler interrogation of
femoral artery flow (sample volume adjusted to the width of
the artery) allowed the determination of flow velocity integrals
(FVI) for each beat by tracing the outline of the
Doppler spectrum.