Pneumatic Self Switching Valve Based Ventilator

grabcad

The ventilator is based on a pneumatic self-switching valving system that connects to a constant pressure source and alternates between an on-state and off-state. During the on-state, a controlled positive pressure and flow are directed to the patient. The flow is cut off by the self-switching valving system to the off-state, at this point expiration is allowed to happen naturally against a constant low positive pressure (maintaining adequate PEEP). Control for switching consists of mechanical components including narrow cross section flow channels and deformable chambers. A network of these components results in a pneumatic self-switching circuit-analog which lends well to simple first order modeling. Further, the tidal volume, I:E and frequency can be adjusted simply by switching between set values of individual components in a predictable manner based on our simulation model. Flow channels and deformable chambers are equipped with sliding walls that enable a dynamic change in dimensions. PEEP values and maximum expiratory pressure are set directly by adjusting inlet pressure values using an off-the-shelf pressure regulator.This ventilator design is unique because it is completely mechanical, and eliminates the need for any electronic components. This enables the system to run independently without any power supply. The assembly does not contain any external moving parts, thus reducing the modes of failure. Furthermore, fabrication and assembly are simplified – the pneumatic control unit consists of two layers made of hard plastics that can be 3D printed, and a membrane that is purchased off-the-shelf. The three components are integrated using the membrane's built-in adhesive. As a result, the entire assembly can be manufactured for a low cost and assembled in a relatively short period of time of a few minutes.Please note: flow_rate_vs_time - flow rate in L/min in versus time in seconds, for I:E of 1:2 and tidal volume of 400cc.