Moisture permeable conduit for a breathing circuit

A limb for a breathing circuit comprising:

• at least one flexible, helically wound conduit for a breathing circuit comprising:
• an inlet,
• an outlet, and
• a tubular structure defining a flow passage between said inlet and said outlet,
• wherein said tubular structure consists of a first helical web and a first helically wound rib,
• wherein the first helically wound rib is heat-bonded to adjacent turns of said first helical web,
• wherein said first helical web has a web thickness of less than 0.5 mm, and
• wherein at least a region of said first helical web is made of a predetermined first polymer material or blend, such that the first helical web is permeable to water vapor and one or more of O2 and CO2, and
• wherein the axial tensile strength of the tubular structure by itself is greater than 40N;
• a first connector mounted at the first end of the at least one conduit;
• and
• a second connector mounted at the second end of the at least one conduit,
• wherein the first connector is provided for connecting to a first device of the breathing circuit and the second connector is provided for connecting to a second device of the breathing circuit.