Recent developments of Opto-Electronic plethysmography allow a noninvasive and accurate measurement of the volume of the chest wall and its different thoraco-abdominal compartments, without any calibration specific on the subject under analysis. OEP provides the complete ventilatory pattern without using any device attached to the subject in any conditions and posture. Combined with pressure and airflow measurements, it can be used to study statics, dynamics and energetics of the chest wall and to estimate possible blood shifts between the thorax and the extremities.