1. Device for determining static mechanical properties of a paralyzed patient's lung comprising pump means communicating with a paralyzed patient's lung to feed to and withdraw from the patient's lung a predetermined gas volume; pressure sensor means connected to said pump means for sensing the gas pressure in the lung; data processing means for processing the volume and pressure data to result in a continuous generation of volume pressure ratio data for determining static mechanical properties of the paralyzed patient's lung; and control means for controlling the pump means.