Arterial stiffness is an important marker of cardiovascular risk. It is measured by pulse wave velocity. The reference device to measure pulse wave velocity is the Sphygmocor which uses applanation tonometry. It is used in adults and children. An easier method called pOpmètre using saturation sensors is validated in adults but not in children. The objective of this study is to compare the pulse wave velocity values measured with the pOpmètre® with those of the SphygmoCor® to validate the pOpmètre in children between 4 and 8 years old.

Prematurity is associated with an increased risk of developing cardio-vascular diseases in adulthood : a low birth weight linked to prematurity is correlated to a higher coronary disease mortality rate, a higher blood pressure level in adulthood, to abnormal glucose metabolism regulation, and to signs of nephron reduction. An independent marker of cardiovascular risk is arterial stiffness: it is associated with a higher risk of major cardiovascular events including stroke, acute coronary syndrome and complications of end-stage renal disease. It is measured by pulse wave velocity which is the gold standard in adulthood. Pulse wave velocity is also correlated to cardiovascular risk in childhood. National cohort EPIPAGE II is made of 4290 premature babies born in 2011. A study is scheduled at 5 years old and a half including a medical examination and a neuropsychological evaluation. An ancillary study lengthening medical consultation for 15 minutes is scheduled with 750 to 1000 of these children for a more precise vascular evaluation including pulse wave velocity. Different methods can be used to measure pulse wave velocity in children: these include applanation tonometry devices such as the SphygmoCor ® system. Its reference values are well known in adulthood and were determined more recently in childhood. It is the reference device but it is expensive, can be used only in expert health centres and time of measurement is long. In children, an easier-to-use and faster device would be more advantageous. The pOpmètre® uses 2 distal oxygen saturation sensors on finger and toe to deduce pulse wave velocity. This device has already been validated in adults. The aim of this study is to validate the pOpmètre in children between 4 and 8 years old. In that purpose, patients are installed in the supine position, at rest. The child's mensurations are measured. The two pOpmètre sensors are put on finger and toe. Blood pressure is measured by an armband on the right limb. Then another armband is put around the thigh and a tonometer is applied on the right carotid which allows pulse wave velocity measuring by the Sphygmocor. Pulse wave velocity is measured with the pOpmètre using the time delay between finger pulse signal and toe pulse signal. The values got with the two devices are compared using a Bland and Altman graph. The pOpmètre is considered to be validated if the 95% confidence interval of the bias is included between -0.5 m/sec and 0.5 m/sec that is about 10% of the normal value at that age (5.0 m/s +/-0.13).

Inclusion Criteria:

• children between 4 and 8 years old hospitalized in the Mother and Children Hospital in Nantes during the study period.

Exclusion Criteria:

• Vasoconstrictor treatment,
• compressive bandage on the measured area,
• peripheral venous access on the measured side,
• vascular surgery or pathology on the measured area,
• significant pain or agitation,
• parental or legal representative disapproval,
• child disapproval.