Monitoring of breathing tube position and patency in situ using reflected sound

A new technique that acoustically interrogates an intubated breathing tube to yield clinically useful patency and position information was developed. A miniature speaker connected to the proximal tube end generates a sonic pulse that propagates down the tube, and the resulting echoes from within the tube and airways are measured by a miniature microphone. During intubations of anesthetized canines, the technique: 1) reliably differentiated between tracheal, bronchial, and esophageal intubations; 2) accurately quantified tube movements; 3) provided the location and degree of lumenal obstructions; and 4) detected extubation or disconnection from the ventilator hose. This technique offers an inexpensive and noninvasive mechanism to monitor breathing tubes in situ.