Abstract: Apparatus for use in a body lumen is provided including an introducer tube configured to be advanced into a gastrointestinal tract of a subject. A guide member is coupled to a distal end of the introducer tube and is configured to be mounted in a vicinity of a valve of the subject. The apparatus also includes a capsule removably coupled to a distal portion of the introducer tube, and configured to be decoupled from the introducer tube and propelled through a small intestine of the subject once the guide member has been mounted in the vicinity of the valve. The apparatus also includes a gas supply configured to propel the capsule distally through the small intestine by generating positive gas pressure proximal to the capsule. Other embodiments are also described.