Pulmonary diseases compromise the lungs function with an impairment of the gas exchange and an alteration of the respiratory mechanic. They are the third leading cause of death after cardiac and neoplastic ones and they have a strongly negative impact on the lifestyle and life expectancy. Inferior vena cava (IVC) ultrasonography (US) can be important in clinical practice to evaluate patients with lungs disorders because IVC reflects changes of intra-thoracic and abdominal pressure and its pulsatility is related to volume status and right atrial pressure. The measures of the diameter of the vein are used to calculate three pulsatility indices: the caval index (CI), the respiratory caval index (RCI) and the cardiac caval index (CCI).