A breathing circuit comprising first and second conduits, wherein at least
one of the conduits is a non-conventional conduit. In an embodiment, a
multilumen unilimb breathing circuit has first and second conduits,
wherein when the proximal ends of said first and second conduits are each
connected to an inlet and outlet fitting, respectively, movement of the
distal end of the first conduit causes a corresponding movement of the
distal end of the second conduit. In an embodiment, at least one of said
conduits is coiled. In another embodiment, a coiled conduit is contained
within an outer flexible conduit that is axially extendable and
compressible, forming a unilimb multilumen respiratory circuit. The outer
flexible conduit may be pleated to provide for non-rebounding axial
extension and contraction. The multilumen respiratory circuit can provide
a variable rebreathing volume. In an embodiment, at least one tube in a
multilumen respiratory conduit is radially collapsible and radially
expandable to a maximum radius for carrying respiratory gases to and from
a patient. The methods and systems can be used to administer anesthesia
and for other purposes.
