The embodiments disclosed herein relate to catheter assemblies. The catheter assemblies can include a multi-lumen catheter, a junction hub, and extension legs. The catheter assemblies can also include a sheath that includes a membrane that is permeable to one or more gases and impermeable to one or more liquids or solids. The catheter assemblies can be configured to deliver food to a patient through a first lumen, and simultaneously vent or aspirate one or more gases from the patient through a second lumen. The catheter assemblies can also include preformed catheters that assume a non-linear three-dimensional shape when in a relaxed state.