Mechanical coupling between the hemithoraces in humans

Abstract

Unilateral airway occlusion permits measurement of single lung function. Since the results suggest that the occluded lung influences the mobility of the contralateral hemithorax, we wanted to test this hypothesis.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 expiration. These measurements were made without and during balloon occlusion of one mainstem bronchus at residual volume (RV) and at total lung capacity (TLC).Unilateral occlusion at RV reduced the ipsilateral diameters in maximal inspiration, but the increase during inspiration was still 39-50% of that without occlusion. The inspiratory increase in contralateral diameters was reduced to 64-80% of the increase without occlusion. Occlusion at TLC reduced the expiratory decrease in ipsilateral diameters to 37-57% of that without occlusion. The expiratory decrease on the contralateral side was reduced to 56-70% of that without occlusion. Due to accompanying mediastinal shifts the parenchymal areas of the occluded lung barely changed. In contrast, the contralateral area was 86-97% of that without occlusion.We conclude that the movement of the two hemithoraces are, at least partially, interdependent. The occluded hemithorax prevents full expansion/compression of the nonoccluded contralateral side, whilst its own mobility appears to be increased by the presence of this nonoccluded side. Potential negative effects are outweighed by the physiological benefit of the coupling, as this mechanism could secure ventilation to a chest half without own movement. Eur Respir J., 1996, 9, 140- In two previous studies on healthy subjects, we occluded one mainstem bronchus with an inflatable balloon and measured the function of the other single lung. When one lung was occluded at total lung capacity (TLC), the other lung could not empty properly [1]. When it was occluded at residual volume (RV), the other lung could not expand fully [2]. These results indicate that the two lungs cannot be at opposite extreme volumes at the same time. The mobility of the rib cage is one of the factors that determine maximal filling and emptying of the lungs [3,4]. When one lung is occluded at RV or TLC, the hemithorax on that side cannot expand or compress properly. We wondered if the reduced mobility on the occluded side also limited the movement of the nonoccluded hemithorax. If so, this could explain our physiological finding.The purpose of the present study was, therefore, to determine how occlusion of a single lung at RV and TLC affects the mobility of the chest wall, both on the occluded and the nonoccluded side. Subjects and methods SubjectsEight healthy volunteers, six females and two males, aged 19-44 yrs, were studied. They had no history of respiratory or cardiac disease or recent airway infection. Their ventilatory lung function was within normal limits as determined by dynamic spirometry on the day of investigation [5]...

Time Course and Pattern of Pulmonary Flow Distribution following Unilateral Airway Occlusion in Sheep

“…Although not specifically alluded to in their papers, the same phenomenon has been observed by others [17, 311. Possible mechanisms include reversal of previous hyperventilation and the combined effect of venous admixture, previous anaesthesia and an occlusion-induced hypomobility of the other hemithorax [32].…”