The invention provides a catheter (12) comprising longitudinally spaced acoustic emitters (S1, S2) and receivers (M1, M2, M3) for use in determining the locations of obstructions in an upper airway of a patient. A plurality of emitters and plurality of receivers are provided, such that, when inserted into an upper airway or oral cavity, the relative attenuation of signals received at each receiver from each emitter may be used to determine the existence and/or extent of obstructions located along the propagation path between each of the various emitter-receiver pairs. Also provided are methods for determining the locations of obstructions in an upper airway using signals received from acoustic receivers as comprised by catheter arrangements according to embodiments of the invention.
