This master thesis aims to correlate breathing and vena cava’s variations. It will be done thanks to a built spirometer and an ultrasound probe used at the same time. It is known that the diameter of IVC (inferior vena cava) varies with cardiac cycle and breathing. Indeed, its diameter tends to increase during inspiration and decrease during inspiration. This happens because of a variation of pressure and the intervention of muscles. Whereas, regarding the cardiac cycle, the diameter is smaller right before atrial systole and it is bigger during atrial contraction. In addition, variation of the IVC is deeply used to analyse and diagnose clinical diseases.