A piston engine includes a feed channel for conducting combustion air to the engine, a collecting container for receiving combustion air from the feed channel, and a feed pipe for conducting combustion air from the collecting container to a cylinder of the engine. These systems and methods can determine appropriate trust levels by comparing applications’ permitted trust levels with their requested trust levels. A syringe is adapted to allow a patient’s blood pressure to move the syringe plunger back towards its starting position, thus enabling a patient’s blood to pass through the injection site.