An intravenous infusion tubing fitment comprises a body, a rotatable knob coupled with the body, and a pressure dome seated within the knob. The body defines; a first inlet configured for coupling with a first segment of tubing; a first outlet into a pressure dome; a second inlet from the pressure dome; and a second outlet configured for coupling with a second segment of tubing. The knob defines an expansion opening within a surface of the knob. The pressure dome is formed of a flexible elastomeric material and defines a fluid flow path between the first outlet and the second inlet. The pressure dome includes a vane configured to variably regulate flow through the fluid flow path in response to rotation of the knob. The pressure dome is configured to expand through the expansion opening in response to fluid pressure in the fluid flow path.