Apparatus and methods are described, including apparatus for treating a maxillary sinus of a subject. The apparatus includes a tube shaped to define a lumen thereof, a lateral wall of the tube at a distal portion of the tube being shaped to define an aperture. A first radially-deployable seal is coupled to the tube proximally to the aperture, and a second radially-deployable seal is coupled to the tube distally to the aperture. Each of the first and second seals is configured to, when radially deployed inside a nasal cavity of the subject, generally prevent flow from one side of the seal to another side of the seal of fluid passing out of the aperture. Other applications are also described.
