Apparatus and methods are described, including apparatus for treating a cavity in a human body, the apparatus including a delivery tube. A barrier device has a collapsed and an expanded configuration, the barrier device moving from the collapsed to the expanded configuration upon being deployed from the delivery tube. A pushing element, slidably disposed within a lumen of the delivery tube, deploys the barrier device from the delivery tube by pushing the barrier device. One or more barrier-deployment elements are coupled to the barrier device and to the pushing element, the barrier-deployment elements being configured to conformingly contact the barrier device with tissue surrounding the cavity. The barrier device is configured to isolate the cavity from surrounding body fluid that is between the barrier device and the pushing element, following deployment of the barrier device from the delivery tube. Other applications are also described.
