Abstract
A plethysmographic method was used to partition the tidal volume into two components: that due to rib-cage expansion and that due to diaphragmatic descent. In 15 normal subjects, one-third of the tidal volume was effected by diaphragmatic descent during various situations, i.e., at rest, voluntary respiratory maneuvers, and breathing special gas mixtures. This technic was combined with measurements of intra-abdominal pressure changes in order to measure the extrapulmonary work done by the diaphragm. For ordinary breathing, this work was found to equal the total extrapulmonary work of breathing (rib cage plus diaphragm) measured by passive ventilation in a body respirator, indicating that the rib cage requires no work to move itself until tidal volumes greater than 1 liter are reached. thorax; work of breathing Submitted on October 24, 1963
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