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Article
October 1938

CLINICAL STUDIES OF RESPIRATIONVII. ADDITIONAL OBSERVATIONS CONCERNING THE VALIDITY OF RESULTS OBTAINED WITH THE BODY PLETHYSMOGRAPH

Author Affiliations

IOWA CITY

From the Department of Internal Medicine, State University of Iowa, College of Medicine.

Arch Intern Med (Chic). 1938;62(4):593-596. doi:10.1001/archinte.1938.00180150049003
Abstract

The use of the plethysmograph in the study of changes in the expiratory volume of the chest has been criticized, and for this reason we wish to report additional observations concerning the validity of this method. Our experiments show that normal persons can be divided into the two following groups: In the first group hyperpnea (voluntary hyperpnea and hyperpnea produced by alteration of the inspired air) is accompanied by a relatively constant oxygen consumption. Spirograms obtained simultaneously with plethysmograms therefore will show the presence or absence of expiratory inflation. In the second group the oxygen consumption is increased during hyperpnea, and the occurrence of expiratory inflation cannot be demonstrated for certain. One may ascertain, however, whether or not expiratory inflation is possible by comparing the volume of the complemental air during rest with the increase produced in the volume of the tidal air during hyperpnea. An increase in the volume

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