I think the best way to get this would be sweep nurbs.
You draw your shape with a spline then get a circle (also in splines) then get a sweep nurbs.
Drop the circle and spline in under the sweep nurbs. So it would look like this.
-SweepNurbs
|circle
|Spline
Then you can still adjust the points on your spline to get the right shape.
And you will have to adjust the diameter on the circle.
If your tube ends up flat more like a smear than a tube you have to swap the “plane” on the circle to another option like ZY or what ever.(only three to choose from).
/randy