Pressure indicating medical injection gun

DETAILED DESCRIPTION The pressure indicating injection gun according to the present invention provides the capability of accurately inflating a balloon catheter with a liquid to a predetermined catheter pressure.
The invention is constructed generally in the form of a gun, or pistol with a barrel clip adapted for holding a conventional disposable hypodermic-type syringe.
A trigger-operated ratchet assembly advances a ratchet shaft in a forward direction so as to push on the syringe plunger and discharge fluid into a balloon catheter.
A coupling shaft connects the syringe plunger to the ratchet shaft by providing at one end thereof a slotted bracket for removable attachment to the syringe plunger rim, and at the other end the coupling shaft is slidable within a cylindrical chamber of the ratchet shaft.
Disposed within the ratchet shaft chamber is a compression spring which acts to allow axial movement of the coupling shaft with respect to and into the ratchet shaft.
The compression spring also includes a known compressibility such that when it is compressed a predetermined amount a desired pressure is known to exist in the balloon catheter.
The coupling shaft includes pressure indicating scale marks along its length to yield visual indications of increasing balloon pressures as the compression spring compresses and the coupling shaft slides into the ratchet shaft spring chamber.
By noting the position of the coupling shaft scale marks with respect to the edge of the spring chamber the pressure within the balloon catheter can accurately be determined.
The barrel of the pressure pistol is contructed of a clear durable plastic so that the pressure marks can be readily seen through the sides or bottom of the barrel.
The barrel also includes an open top so that the pressure indicating marks on the coupling shaft can be readily seen from the top of the instrument.
A full length hand trigger is pivotal at one end thereof and actuates a ratchet mechanism which engages teeth on the ratchet shaft so that the shaft can be advanced, and through the coupling shaft and compression spring, the syringe plunger is urged forwardly to force fluid into the balloon catheter