Evaluation of Methods of Estimating Sub-Glottal Air Pressure

Abstract

The following measures were simultaneously recorded as each of 10 adult male subjects phonated vowels at a variety of frequency and intensity levels: (a) intraesophageal pressure sensed by a small balloon inserted into the esophagus, (b) intratracheal pressure sensed by a hypodermic needle inserted into the trachea, and (c) lung volume recorded by a respirometer. The study tested the validity of obtaining subglottal air pressure: (a) through the direct use of intra-esophageal pressure values, (b) through the use of the drop in intra-esophageal pressure which results when phonation is interrupted with the vocal folds abducted, and lung volume held constant, and (c) through the use of intra-tracheal pressure values. Results suggest that method (b) provides a valid estimate of subglottal pressure under conditions of sustained phonation, while method (c) provides a valid and reliable measure during sustained phonation and during connected speech where changes being recorded occurred at syllabic rates. Under no experimental conditions did method (a) provide a valid estimate of subglottal pressure.