Methods and devices for safely positioning a needle syringe in a body cavity

A pressure-dependent clutching device for automatically engaging and disengaging a force-applying structure so that a driving force will not drive a needle in an engaging state and will drive the needle in a disengaging state, wherein the driving force is from the needle depending on an external pressure encountered by the needle, comprising:

• a body having an interior space;
• a pressure-sensing element defining a portion of a pressure chamber disposed in the interior space for sensing the external pressure, said pressure-sensing element is adapted to switch between a first configuration corresponding to a first pressure state and a second configuration corresponding to a second pressure state;
• and
• a force-receiving element operatively connected to the pressure-sensing element, said force-receiving element is configured to have a complementary structure to a force-sending element that is operatively connected to the force-applying structure for a user to apply the driving force,
• wherein during operation, the needle is coupled to the force-applying structure via the pressure dependent clutching device and the pressure-sensing element is placed in pressure communication with the external pressure such that when the external pressure crosses a threshold level, the pressure-sensing element is caused to switch from one configuration to the other which in turn causes the force-receiving element to engage or disengage from the force-sending element resulting in the driving force applied at the force-applying structure drives or does not drive the needle.