The Effect of Posture on Diaphragmatic Movement and Vital Capacity in Normal Subjects

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Abstract
A simultaneous recording of diaphragmatic movement and respiration was made on 12 normal subjects placed in a sequence of postures from standing to lying tilted 45[degree] head down. Although there was considerable lifting of the diaphragm with change from upright to head down postures, diaphragmatic movement (excursion) changed only slightly, moving about 1.5 cm. on quiet breathing and about 6-7 cm. on deep breathing. The deep breathing movements,"reserve movements," decreased appreciably as the individual assumed the lower stance and are related to the decrease in the reserve air. A good relationship between radiological chest volumes and the volumes measured spirometrically could only be obtained if care were taken to take the radiographs when subjects had inspired or expired completely. The authors advise spirometric control for achieving this relationship.