Apparatus for delivering foam

Abstract

Apparatus, e.g. a syringe, for dispensing foam includes means for ensuring that only foam of adequate quality is dispensed. In use, the syringe may be filled from a pressurised canister which generates foam e.g. for therapeutic use in treating varicose veins. An initial quantity of foam dispensed from the canister may be of inadequate quality in which case it should not be used: the syringe includes means to ensure that this initial quantity of foam is diverted to a waste port or to an internal waste chamber e.g. located in the syringe plunger. Foam dispensed after the initial quantity of poor quality foam is stored in the main barrel of the syringe ready for administration to a patient in need of treatment.

1 . A syringe for dispensing foam comprising:
 (a) a syringe plunger having a waste chamber communicating with an inlet in a front face of the plunger; and   (b) a syringe barrel having a nozzle and a bore to receive the plunger.   
     
     
         2 . A syringe as claimed in  claim 1  wherein the internal waste chamber is provided with a vent which comprises either a hydrophobic vent or a hole in a wall of the chamber. 
     
     
         3 . A syringe as claimed in  claim 1  wherein the chamber has one or more flexible walls. 
     
     
         4 . A syringe as claimed in  claim 3  wherein the chamber is substantially empty of air. 
     
     
         5 . A syringe as claimed in claimed in  claim 3  wherein the chamber is retained within a rigid walled chamber or frame comprising part of the plunger. 
     
     
         6 . A syringe as claimed in  claim 3  wherein the said flexible wall or walls is/are substantially inextensible. 
     
     
         7 . A syringe as claimed in  claim 1  wherein the inlet to the chamber is adjacent the syringe nozzle when the plunger is in its fully depressed state. 
     
     
         8 . A syringe as claimed in  claim 3  wherein the flexible chamber is contained within a space defined by rigid walls of the plunger, and vents are provided in the said rigid walls to allow air between the chamber walls and the said rigid plunger walls to escape when the chamber is filling with foam. 
     
     
         9 . A kit for providing a syringe full of foam, the kit comprising a syringe as claimed in  claim 1  together with a source of foam. 
     
     
         10 . A kit as claimed in  claim 9  wherein the source of foam is a pressurised canister containing liquid to be foamed and gas under pressure. 
     
     
         11 . A method of dispensing foam using a syringe as claimed in  claim 1  comprising the steps of:
 (a) connecting the syringe to a source of foam; and 
 (b) dispensing a continuous flow of foam into the syringe from the source; 
 (c) whereby the flow of foam initially enters the waste chamber such that foam fills or substantially fills the said waste chamber; and 
 (d) the flow of foam subsequently pushes the syringe plunger back in the syringe barrel and starts to fill the syringe.