A new approach to mechanical simulation of lung behaviour: pressure-controlled and time-related piston movement

A mechanical lung simulator is described (an extension of a previous mechan ical simulator) which simulates normal breathing and artificial ventilation in patients. The extended integration of hardware and software offers many new possibilities and advantages over the former simulator. The properties of components which simulate elastance and airway resistance of the lung a re defined in software rather than by the mechanical properties of the comp onents alone. Therefore, a more flexible simulation of non-linear behaviour and the cross-over effects of lung properties is obtained. Furthermore, th e range of lung compliance is extended to simulate patients with emphysema. The dependency of airway resistance on lung recoil pressure and transmural pressure of the airways can also be simulated. The new approach enables on e to incorporate time-related mechanics such as the influence of lung visco sity or cardiac oscillation. The different relations defined in the softwar e can be changed from breath to breath. Three simulations are presented: (1) computer-controlled expiration in the artificially ventilated lung; (2) simulation of normal breathing; and (3) s imulation of viscoelastance and cardiac influences during artificial ventil ation. The mechanical simulator provides a reproducible and flexible enviro nment for testing new software and equipment in the lung function laborator y and in intensive care, and can be used for instruction and training.