Bellows-less lung system for the human patient simulator.

A new bellows-less lung simulator utilising a fixed-volume pressure controller to simulate spontaneous breathing is presented as an alternative to the traditional bellows-driven mechanical lung system in the human patient simulator (HPS). The HPS is a fully interactive, life-like simulator used to train medical students and anaesthesia residents. The lung simulator simulates carinal pressure, which allows for simulation of actively breathing or ventilated patients. In the current HPS implementation, breathing is physically simulated with a pair of bellows and a computer-controlled piston, but, owing to physical and dynamic constraints, the model suffers from a lot of dead space. Furthermore, the set-up incorporates several mechanical components that require time-consuming calibrations, which drives up manufacturing costs. A bellows-less lung simulator has been designed and built which successfully simulates airflow in and out of the mouth by controlling the carina pressure. The new system is able to simulate tidal volumes between 400 and 500 ml, with flow rates of 4.3-5.71 min(-1) at a respiratory rate of 12 breaths per minute. The new design not only matches the ventilation performance of the HPS, but also simulates at 60 breaths per minute, which the HPS cannot maintain.