Fluid vessel communication device

1. A fluid vessel insertion device comprising:

a sleeve attached to the fluid vessel insertion device in a fixed position; and

a linearly movable puncture member configured to be located within the sleeve;

a retractor configured for actuating the puncture member relative to the sleeve-between:

a first condition in which an end of the puncture member protrudes beyond an end of the sleeve such that the puncture member may be inserted into the body of a patient, and

a second condition in which the end of the puncture member is within the sleeve, wherein the end of the puncture member is a puncturing end with a first aperture for insertion into a fluid vessel in use;

wherein the retractor comprises an internal chamber, the puncture member extending into the internal chamber and comprising a second aperture, which second aperture is in fluid communication with the first aperture, for fluid communication between the first aperture and the interior of the internal chamber, and a pressure sensor in the form of an inflatable member coupled to, or formed with, the internal chamber, the inflatable member being movable relative to walls that define the internal chamber in response to fluid pressure in the internal chamber;

wherein said internal chamber is sealed from the exterior of the device except via the first aperture, and the internal chamber is maintained at an ambient pressure when the device is in an at-rest state,

wherein retraction of the puncture member by the retractor from the first condition to the second condition is caused in response to the inflatable member sensing a positive external fluid pressure at the end of the puncture member that is greater than a predetermined pressure difference from ambient pressure,

wherein the inflatable member is connected to a peripheral wall defining another chamber in fluid communication with the internal chamber,

wherein the another chamber has a generally cylindrical shape, and

wherein the inflatable member is movable relative to the peripheral wall.

2. The device according to claim 1 , wherein the puncture member is hollow to allow said fluid communication between the first and second apertures.

3. The device according to claim 1 , wherein the puncture member comprises a needle.

4. The device according to claim 1 , comprising a housing comprising the retractor and the pressure sensor, wherein the internal chamber is entirely contained within the housing, and wherein the puncture member depends from the housing to its puncturing end.

5. The device according to claim 1 , wherein the internal chamber is maintained at substantially ambient pressure in the at-rest state and the device is configured to trigger the retractor to actuate the puncture member into the second condition when a pressure gradient is experienced between an interior of the internal chamber and an external pressure at the end of the puncture member.

6. The device according to claim 1 , wherein the inflatable member comprises a diaphragm.

7. The device according to claim 6 , wherein the internal chamber comprises a rigid wall structure and the diaphragm comprises a flexible wall.

8. The device according to claim 6 , wherein the internal chamber comprises a first portion of reduced width and a second portion of enlarged width, the diaphragm spanning the second portion of the internal chamber.

9. The device according to claim 1 , wherein the retractor comprises an engagement member arranged to releasably engage the puncture member dependent on the pressure within the internal chamber.

10. The device according to claim 9 , wherein the puncture member is biased towards the second condition and is releasably held in the first condition by the engagement member.

11. The device according to claim 1 , comprising a stop member arranged to limit travel of the puncture member by the retractor to a predetermined distance.

12. The device according to claim 11 , wherein the stop member is located in the internal chamber of the retractor and braced against a rear wall of the internal chamber when the retractor is in the second condition.

13. The device according to claim 12 , wherein the stop member has a frustoconical shape.

14. The device according to claim 12 , wherein the stop member is biased in a retraction direction by a biasing member disposed in the recess.

15. The device according to claim 1 , comprising a housing for the retractor, wherein the puncture member depends from the housing such that a first end of the puncture member is spaced from the housing and a second end of the puncture member is mounted in the housing.

16. The device according to claim 1 , wherein the inflatable member is a diaphragm sandwiched between two opposing discs.

17. The device according to claim 16 , wherein a pin is integrally formed with an outer disc of the two opposing discs and extends through the diaphragm and an inner disc of the two opposing discs towards the internal chamber, and

wherein a guide formation is provided within a throat through which the pin extends into the internal chamber.

18. The device according to claim 1 , wherein the retractor further comprises an engagement member releasably engageable with the puncture member, the engagement member actuable by the inflatable member in response to sensing a positive external fluid pressure, which is greater than a predetermined pressure difference from ambient pressure, at the end of the puncture member.

19. The device according to claim 18 , wherein the puncture member comprises an engagement formation for cooperation with the engagement member.