The rib cage in normal and emphysematous subjects: a roentgenographic approach

The configuration and motion of the bony rib cage were studied from lateral chest roentgenograms in 10 young normal subjects (YN), 12 elderly normal subjects, and 12 hyperinflated emphysematous patients [chronic obstructive pulmonary disease subjects (COPD), mean total lung capacity (TLC) 133% of predicted]. The acute angles formed by the fourth through seventh ribs with an axial reference plane were measured at residual volume, functional residual capacity, and TLC in both supine and standing positions and correlated with corresponding lung volumes. both rib angles (RA) and changes in RA with lung volume were greatest with the fourth rib and decreased progressively going down (caudad) the chest. At TLC the RA of upper ribs was significantly less in EN and significantly greater in COPD than in YN. RA's were greater supine than standing. When RA information was used together with autopsy data on the angles formed by intercostal muscles with adjacent ribs, intercostal muscle lengths in hyperinflation could be calculated. Computed intercostal muscle length data suggested that hyperinflation should not be associated with degrees of intercostal muscle shortening or overstretching, that would interfere seriously with tension generation.