The Influence of Costal and Abdominal Pressure on the Action of the Diaphragm in Normal and Emphysematous Subjects

Abstract

In 3 groups of individuals[long dash](1) the normal, 8 medical students;(2) 25 individuals suffering from severe to moderate emphysema; (3) 9 obese asthmatics[long dash]the author measured the highest and lowest level that could be reached by the diaphragm in (a) max. expiration and inspiration,in the sitting and supine position, and (b) during quiet breathing. The same measurements were then taken during costal and abdominal pressure. Respiratory tracings were taken with a recording spirometer of the Benedict-Roth type. In normal subjects the diaphragm would change its range of motion under pressure. With costal pressure the diaphragm could be lowered more than previously possible and with abdominal pressure the diaphragm could be forced higher into the thorax. In severe emphysema, however, the diaphragm cannot be pushed further down in the abdomen by costal pressure and the diaphragm could not be pushed as high in the thorax by abdominal pressure as in normal subjects. The diaphragmatic level in obese subjects was approx. the same as in normal subjects, but the range of motion was somewhat restricted and the diaphragm could not be lowered, thus indicating that the lowest level had been reached. Under abdominal pressure the diaphragm can be lifted satisfactorily. In studying the vital capacities it was noted in the normal subjects and the emphysematous subjects that costal pressure always caused a pronounced decrease in vital capacity, whereas the reduction of vital capacity by abdominal pressure, though present, was much less. In no case did costal or abdominal pressure increase vital capacity. The author finds it difficult to offer an explanation for the subjective improvement during compression, but suggests that the pressure may cause certain parts of the lungs to be ventilated more than before.