Upper and lower rib cage deformation during breathing in quadriplegics.

In quadriplegia, the anteroposterior diameter of the rib cage (RC) decreases during inspiration. Our aim was to characterize this paradoxical motion further and to determine to what extent it was due to a diminished inspiratory effect of the diaphragm on the RC because of abdominal muscle paralysis. In six quadriplegics, upper and lower RC (URC, LRC) displacements were studied in various postures with and without extrinsic abdominal support. LRC was in its relaxed configuration at all lung volumes studied in three subjects before and four subjects during abdominal compression. URC distorted most and, despite improvement during abdominal compression, was never in the relaxed configuration during tidal inspiration. Thoracic distortability was further studied by noting the effect on URC and LRC of a cephalad force applied to the RC at the costal margin. This produced distortion similar to that observed during spontaneous inspiration. It was concluded that during spontaneous inspiration in quadriplegics lack of abdominal support does not entirely explain the RC distortion which occurs, and high abdominal pressure results in diminished RC distortion, an effect which we attribute to an increase in the area of diaphragmatic apposition to the RC.