Wind turbine blade comprising a shape modifiable airfoil section that extends both chordwise and spanwise and has a not modified default shape, a conduit that extends from the inside of the blade towards the outside of the blade, and an outer part comprising a flow regulator that is located at the shape modifiable airfoil section and blocks the conduit when the shape modifiable airfoil section presents its default shape, and does not block the conduit when the shape modifiable airfoil section presents a modified shape. In the latter situation the conduit is opened to the outside of the blade and a device for exchanging a fluid between the inside and the outside of the blade is thus defined.