A new frontier in plethysmography for the measurement of lung ventilation distribution and the study of respiratory mechanics. BTS OEP SYSTEM is a truly innovative investigation tool which supplies accurate measurement of the abdominal-thoracic wall total volume and of pulmonary volume changes, breath by breath, all through long periods of time, with no need of a mouthpiece and in a non-invasive way. It can be used during static tasks as well as physical exercise on the ergometer or treadmill.