Trocar entry incorporating an airbag

1. An airbag cannula comprising:

a cannula having a housing and an elongate tubular member extending distally from the housing;

an expandable member positioned on the elongate tubular member proximal of a distal end of the elongate tubular member, the expandable member movable from a collapsed position to an expanded position;

a sensor disposed within the housing, the sensor having a sensor lumen extending therefrom, the sensor lumen formed through the elongate tubular member and having a sensor opening adjacent to the distal end of the elongate tubular member distal of the expandable member; and

a trigger mechanism operatively associated with the sensor and the expandable member such that a change of condition sensed at the sensor opening operates to move the expandable member from the collapsed to the expanded position.

2. The airbag cannula as recited in claim 1 , wherein the expandable member is an airbag positioned on the elongate tubular member, the elongate tubular member including an inflation lumen in fluid communication with the airbag, wherein the trigger mechanism includes a valve to inflate the airbag in response to a change in conditions detected by the sensor.

3. The airbag cannula as recited in claim 2 , wherein the sensor is an air pressure sensor configured to detect changes in air pressure at the sensor opening.

4. The airbag cannula as recited in claim 2 , wherein the sensor is an optical sensor including an optical fiber extending through the sensor lumen and terminating adjacent the sensor opening.

5. The airbag cannula as recited in claim 2 , wherein the sensor is an ultrasound sensor.

6. The airbag cannula as recited in claim 2 , wherein the sensor is a sonar sensor.

7. The airbag cannula as recited in claim 2 , wherein a distal end of the airbag is longitudinally movable along and outer surface of the elongate tubular member.

8. The airbag cannula as recited in claim 2 , wherein the airbag includes a plurality of circumferentially spaced airbags.

9. The airbag cannula as recited in claim 2 , further comprising an outer sheath overlying the airbag to restrain the airbag in the collapsed position.

10. The airbag cannula as recited in claim 9 , wherein the outer sheath includes a perforation line which is separable upon inflation of the airbag from the collapsed to the expanded position.

11. The airbag cannula as recited in claim 2 , further comprising a source of fluid pressure operatively associated with the valve.

12. An airbag cannula comprising:

a cannula having a housing and an elongate tubular member extending distally from the housing;

an expandable member positioned on the elongate tubular member proximal of a distal end of the elongate tubular member, the expandable member movable from a collapsed position to an expanded position;

an inflation lumen extending at least partially through the elongate tubular member and being disposed in fluid communication with the expandable member;

a sensor disposed within the housing, the sensor having a sensor lumen extending therefrom, the sensor lumen formed through the elongate tubular member and having a sensor opening adjacent to the distal end of the elongate tubular member; and

a trigger mechanism operatively associated with the sensor and the expandable member such that a change of condition sensed at the sensor opening operates to move the expandable member from the collapsed to the expanded position, the trigger mechanism being disposed in fluid communication with the inflation lumen.

13. The airbag cannula as recited in claim 12 , wherein the trigger mechanism includes a valve in fluid communication with the inflation lumen, the valve adapted to provide fluid to the inflation lumen upon a change of condition sensed at the sensor opening.

14. The airbag cannula as recited in claim 13 , wherein the trigger mechanism includes a trigger operatively associated with the sensor and the valve, the trigger adapted to actuate the valve upon a change in pressure detected by the sensor.

15. The airbag cannula as recited in claim 12 , wherein the trigger mechanism is fluidly connected to the inflation lumen by a tube external to the elongate tubular member.

16. The airbag cannula as recited in claim 15 , wherein the inflation lumen defines an opening on a exterior surface of the elongate tubular member for receiving the tube.

17. An airbag cannula comprising:

a cannula having a housing and an elongate tubular member extending distally from the housing;

an expandable member positioned on the elongate tubular member proximal of a distal end of the elongate tubular member, the expandable member movable from a collapsed position to an expanded position;

a sensor disposed within the housing, the sensor having a sensor lumen extending therefrom, the sensor lumen formed through the elongate tubular member and having a sensor opening adjacent to the distal end of the elongate tubular member, the sensor opening being positionable against tissue; and

a trigger mechanism operatively associated with the sensor and the expandable member such that a change of condition sensed by the sensor operates to move the expandable member from the collapsed to the expanded position.

18. The airbag cannula as recited in claim 17 , wherein the sensor is an air pressure sensor configured to detect changes in air pressure at the sensor opening and within the sensor lumen.

19. The airbag cannula as recited in claim 17 , wherein the sensor is adapted to pressurize the sensor lumen upon positioning of the sensor opening against tissue.

20. The airbag cannula as recited in claim 19 , wherein the change of condition sensed by the sensor is the pressurization of the sensor lumen.