The density of the foam can be varied to suit the therapeutic context, determined beforehand, by altering the volumes of sclerosing liquid and sterile air or gas initially introduced into the disposable syringe.
For this, it is necessary to take into account both the concentration of the sclerosing liquid and the ratio between the volume of sclerosant and sterile air or gas introduced into the disposable syringe.
For sclerosing liquids with a concentration between 0.125% and 0.50%, the quantity of liquid can vary from 0.25 to 0.4 ml for a total volume in the syringe (liquid +air) of 2.5 ml. The sterile foam obtained with 0.25 ml of liquid and 2.25 ml of sterile air or gas would have a denser texture, and the one obtained with 0.4 ml of liquid and 2.1 ml of sterile air or gas would have a softer texture.
For sclerosing liquids at a concentration of between 0.5% and 1%, the volume of liquid can be varied from 0.4 ml to 0.7 ml for a total volume in the syringe (liquid +air) of 5 ml.
The sterile foam obtained will be more compact with 0.4 ml of fluid and 4.6 ml of sterile air or gas than with 0.7 ml of fluid and 4.3 ml of sterile air or gas, which will form a more unctuous sterile foam.
Finally, liquid sclerosants at a concentration of 1% to 3%, the volume of fluid can be varied from 0.8 ml to 1.4 ml for a total volume in the syringe (liquid + air) of 10 ml.
The sterile foam obtained with 0.8 ml of sclerosant and 9.2 ml of sterile air or gas will be more dense than one obtained with 1.4 ml of sclerosant and 8.6 ml of sterile air or gas.
It is also important to remember to take into account the fact that STS foams more readily than to POL, by slightly increasing the quantity of sterile air or gas with respect to the dose of liquid sclerosant.
The initial volume of liquid sclerosant is determined on the basis of several criteria :
- the volume of syringe chosen,
- the concentration of the proposed sclerosants,
- the required texture of the foam, which itself depends on the diameter of the varicose veins to be treated.
Density of the foam : summary table
|Concentration of neat or diluted sclerosing liquid
|0,125 % - 0,50 %
0,50 % - 1 %
1 % - 3 %
|Volume of sclerosing liquid to draw up into the syringe
|0,30 ml-0,35 ml
|0,50 ml-0,60 ml
|1,00 ml-1,20 ml
|Volume of sterile air or gas to introduce into the syringe
|2,20 ml-2,15 ml
|4,50 ml-4,40 ml
|9,00 ml-8,80 ml
|Quality of sterile foam obtained