ACOUSTIC MEASUREMENT OF SUBGLOTTIC STENOSIS

A device that determines cross-sectional area (CSA) of the airway by a coustic reflections (Hood, Inc) was used to measure subglottic area. A irway models were made from Plexiglas rings with known internal dimens ions similar to clinically encountered stenoses of various lengths and diameters. Acoustic measurements of airway area were made and compare d to actual CSA. There is a strong correlation between CSA measured ac oustically and the actual area of simulated stenoses. However, when th e CSA of the stenosis was <0.64 cm(2), the signal was impaired, result ing in overestimation of the stenotic CSA. In simulated stenoses with a CSA of <0.38 cm(2), acoustic measurement of the CSA beyond the steno tic segment was unreliable. Determination of the origin of stenosis wa s accurate with this method. The CSA of cadaver airways was also measu red acoustically. The CSA 2.0 cm below the glottis of normal airways i n males ranged from 1.28 to 2.74 cm(2) and in females 0.87 to 1.43 cm( 2), with means of 2.16 and 1.09 cm(2). It appears that acoustic measur ement of CSA of subglottic stenosis is a feasible clinical technique t hat yields dimensions of the airway in situations in which direct meas urements are impossible. It was suggested that this technique be used for assessment of subglottic stenosis and evaluation of the efficacy o f treatment of subglottic stenosis.