EXPIRATORY PRESSURES AND AIR FLOW DURING SPEECH
Journal/Book: Reprinted from the British MEDICAL JOURNAL June 18 1960 vol. i pp. 1837-1843. 1960;
Abstract: From the Departments of Physiology and Phonetics University of Edinburgh Summary Methods are described for estimating the tracheal pressure during speech and of recording activity in the diaphragm and a variety of thoracic and abdominal muscles. During a steady level of loudness of speech the mean tracheal pressure is kept remarkably steady. The pressure needed varies from 2 cm. of water for very quiet speech to 30 cm. for parade-ground shouting. To attain a steady level of 2 cm. of water throughout an expiration the inspiratory muscles-the external intercostals-at first oppose the relaxation pressure (there is usually a short period when all muscles are inactive and the relaxation pressure acts alone); then expiratory muscles beginning with the internal intercostals and later involving other muscles. such as the rectus abdominis reinforce the diminishing relaxation pressure. In paraplegics the maximal expiratory pressure that can be exerted is lower the higher the level of transection between T 12 and C 6. The shortest reaction time when a subject was instructed to say "ma" as soon as possible after a sound was 140 msec. to the start of internal intercostal muscle activity. The first sound started consistently about 50 msec. later. We are indebted to Dr. Ludwig Guttman for permission to examine some of his paraplegic patients. We thank Mr. C. Shepley department of medical Illustration University of Edinburgh for his assistance with Fig. 1 and Mr. W. T. S. Austin for his technical assistance throughout this study.