To change the solubility of gas in a liquid you have to change the chemistry of the liquid, since the solution event is going on not physically, but chemically between moieties of liquid and gas. And since it does not depend on the physical characteristics, for which we can insert the capillary effect, it should not change the solubility of gases either.

I hope it gave you some ideas,

With best regards.

Surface tension determines the shape of the liquid meniscus, which increases the surface area exposed to the liquid. This is for fluids which wet the solid as with water and glass. Higher surface area leads to higher evaporation rates and more of a soluble gas will dissolve into the water for the same reason. Your previous commentor is referring to the Kelvin effect which raise the vapor pressure in quite small capillaries. This will lower the solubility of a gas close to the interface because the gases partial pressure is less. Shy of the boiling point of the liquid these effects are small. So the effects are subtle but small.

Thanks for the answers. My feeling is that solubility of gas in a liquid restrained into a capillary, small enough so to produce a significant change on its vapor pressure, should decrease wrt its value for a free surface. In an equilibrium state, if vapor pressure of the liquid decreases due to caplillarity (weeting systems in capillaries), then gas from the liquid should be released to compensate for such drop and hence, the amount remaining in the liquid will go down,,,but then, what about the exchange of O2 and CO2 in the very narrow blood vessel at the lungs, for example?