MECHANICAL COUPLING BETWEEN THE HEMITHORACES IN HUMANS

Unilateral airway occlusion permits measurement of single lung functio n, Since the results suggest that the occluded lung influences the mob ility of the contralateral hemithorax, We wanted to test this hypothes is, In eight healthy subjects, we measured, using computed tomography, lung parenchymal area and inner rib cage parasagittal and transverse diameters at three different levels and at maximal inspiration and exp iration, These measurements were made without and during balloon occlu sion of one mainstem bronchus at residual volume (RV) and at total lun g capacity (TLC). Unilateral occlusion at RV reduced the ipsilateral d iameters in maximal inspiration, but the increase during inspiration w as still 39-50 % of that without occlusion. The inspiratory increase i n contralateral diameters was reduced to 64-80 % of the increase witho ut occlusion, Occlusion at TLC reduced the expiratory decrease in ipsi lateral diameters to 37-57 % of that without occlusion, The expiratory decrease on the contralateral side was reduced to 56-70 % of that wit hout occlusion, Due to accompanying mediastinal shifts the parenchymal areas of the occluded lung barely changed, In contrast, the contralat eral area was 86-97 % of that without occlusion, We conclude that the movement of the two hemithoraces are, at least partially, The occluded hemithorax prevents full expansion/compression of the nonoccluded con tralateral side, whilst its own mobility appears to be increased by th e presence of this nonoccluded side, Potential negative effects are ou tweighed by the physiological benefit of the coupling, as this mechani sm could secure ventilation to a chest half without own movement.