Figure 1.

Working mechanism of Ventrain (expiratory ventilation assistance technology). (A) Equilibration mode. The gas flows via the inlet (1) through a very narrow nozzle (2) towards the exhaust pipe (3). No flow from or to the patient. (B) Closing both the exhaust pipe (3) and safety bypass (5) forces the oxygen to flow via the inlet (1) through the narrow nozzle (2) towards the patient via port (4): inspiration. (C) Expiration: The gas flows via the inlet (1) through a very narrow nozzle (2) and exhaust pipe (3) to the outside. The flow entrains gas from port (4), which is connected to a catheter: active expiration. The bypass (5) functions as an on/off switch. When opened, there is no significant positive or negative pressure at the catheter tip, resulting in equilibration/safety mode.