Thoracoabdominal mechanics during tidal breathing in normal subjects and in emphysema and fibrosing alveolitis.

Thoracoabdominal motion and intrathoracic (oesophageal), intra-abdominal (gastric), and transdiaphragmatic pressures were measured during tidal breathing in 20 erect subjects--six normal, seven, with emphysema, and seven with fibrosing alveolitis. In normal subjects all diameters increased synchronously during inspiration and were accompanied by rises in abdominal and transdiaphragmatic pressures. Five patients with fibrosing alveolitis showed a reduction in upper ribcage motion, but normal lower ribcage and abdominal motion; stiff fibrotic lungs may sometimes impair the ability of the diaphragm to expand the upper ribcage and result in proportionally more expansion of the bases. Four emphysematous patients showed increased anteroposterior motion of the ribcage and four showed paradoxical inward motion of the lower ribcage during inspiration. These changes apparently result from increased activity of intercostal and accessory muscles and altered configuration of the diaphragm. The muscles of patients with large, overinflated lungs are at a greater disadvantage than those with small fibrosed lungs.