To analyze vascular function and related functional parameters on humans, several methods have been implemented on the technical platform “exploration of vascular function” since 2010. The development of these non-invasive techniques has been performed in collaboration with the Clinical Investigation Centre (CIC) in Clermont-Ferrand (Prof. C. Dubray, Vascular medecine) and the Department of Cardiology at the University Hospital of Clermont-Ferrand (Prof. J.R. Lusson, Dr Nicolas Barber- Chamoux). An engineer from the Human Nutrition Unit, Marie-Anne Verny, has been trained to these techniques by specialists and is fully competent to realize all the vascular measurements required in clinical trials.

The platform is localized at the CIC.   

Equipment and measurements:

The technical platform is equipped with the following devices to assess vascular function with non-invasive techniques:

Vivid S5 echocardiograph (GE)

• Flow Mediated Dilatation (FMD) and blood flow velocity

In the macro-circulation, endothelial function is evaluated after the induction of reactive hyperemia by measuring FMD and blood flow velocity at the brachial artery with an ultrasound Doppler (VIVID S5 GE).

FMD (%) = ((artery maximum diameter – artery basal diameter)/artery basal diameter)*100

• Intima/media thickness

The thickness of the carotid intima-media is closely correlated with the occurrence of cardiovascular events. This parameter is measured by ultrasound (VIVID S5).

Endo-PAT 2000 (Itamar Medical Ltd)

In the peripheral arterial beds, endothelial function is assessed after the induction of reactive post occlusive hyperemia using peripheral arterial tonometry (Endo-PAT 2000, Itamar). The measurement of the endothelium-mediated changes in vascular tone is made in the fingertips using a pair of unique plethysmography-based bio-sensors.

The results were expressed as reactive hyperemia index (RHI, %), which correspond to the ratio between the average pulse wave amplitude during hyperemia (60 to 120 s of the post-occlusion period) and the average pulse wave amplitude during baseline in the occluded hand and corrected by the values from the control arm.

Normal: RHI > 1.67
Abnormal: RHI ≤ 1.67

The EndoPAT device also generates the augmentation index (AIx), which is a measure of peripheral microvascular stiffness calculated from the shape of the pulse wave recorded by the probes during baseline. To correct for the independent effect of heart rate, the AIx is adjusted to a heart rate of 75 beats/min (AIx@75 beats/min).  Measures arterial stiffness is considered an independent risk factor for CVD not necessarily correlated to endothelial function. Lower AI values (including negative results) reflect better arterial elasticity.

Periflux (Perimedes SA)

Changes in microcirculation are measured by the Flow Laser Doppler techniques using the Laser Doppler PF 5010 (Perimed). The Laser Doppler analyses overall blood perfusion at a defined point. It is an excellent technique to monitor the changes caused by the induction of post occlusive reactive hyperemia, local heat or iontophoresis.

SphygmoCor (CPV ATCOR Medical)

Arterial stiffness is considered to be the main factor in arterial aging and a major risk factor for CVD. This parameter is assessed by measuring the velocity of a pulse wave (Pulse Wave Velocity, PWV) between the carotid and femoral artery. The PWV value is proportionally correlated to arterial stiffness.