Some observations on the coordination of diaphragmatic and rib movement in respiration.

Tracings of the respiration were made with a spiromefer of the Benedict-Roth type to which a flowmeter was attached. Oxygen was supplied continuously through this flowmeter at the same rate at which it disappeared from the spirometer. The tracings were thus kept horizontal. After quiet breathing had been recorded for some minutes the subject was asked,to inhale and exhale fully, and the vital capacity was recorded. This was repeated several times at intervals of one minute or more. At the same time the rib movements were recorded by means of the thoracograph described by Verzir (1945). This instrument permits the accurate tracing of any change in the circumference of the chest at any given level.* It is therefore possible to state how much the chest expands or contracts during a single tidal breath, or during a full inspiration or expiration. The tracing thus appears very similar to a spirometric tracing, showing the level at which the tidal air exchange occurs between the limits of inspiration and expiration (Plate Ia). But unlike the spirometric tracing it does not represent a volume of air moved but the changes in the circumference of the chest at a certain level. If the tidal air level moves up or down it means that normal quiet breathing is carried out by a more or less inflated chest. As a rule the instrument was applied at the level of the third to fourth ribs.