Abstract: Apparatus and method for selectively blocking respiratory airflow to a pediatric lung or a single lobe thereof. The apparatus comprises an endotracheal tube adapted for passage of a bronchoscope therethrough and a second flexible tube which is parallel with and fixedly contacting said endotracheal tube. A bronchial blocker assembly, having a pair of axial passageways therethrough, is provided which is insertable into and movable along the length of said second flexible tube. One of said axial passageways receives a stylet, said stylet being movable along the length of and rotatable within said axial passageway. Said stylet being sufficiently flexible to guide said endotracheal tube and said bronchial blocker assembly along a pediatric patient's windpipe. Means are provided for fixing said bronchial blocker assembly relative to said second axial passageway when said bronchial blocker assembly is resident therewithin.