The suction mechanism as a factor in intrathoracic oedema, connective tissue or pleural effusion.

In pathological conditions, the negative intrapleural pressures (Ppl) may increase unequally. At some sites they may remain increased. We maintain that at these sites the increased pressures may lead to the production of oedema in the adjacent pleural walls and in adjacent pre-existing connective tissue, which may remain as oedema or may become connective tissue. Occasionally the increased negative Ppl may contribute to the production of pleural effusion. We term all these processes the suction mechanism (SM). This mechanism affords an interpretation of a series of images observed in chest X-rays. According to this view, lung shrinkage, narrowing of the pulmonary vessels and impairment of the lung function are not caused by the diffuse pleural fibrosis, but result from damage to the lung parenchyma. We also interpret the apical cap, the blunting of the costophrenic sulci, the broadening of the mediastinum and the retrosternal stripe in terms of the SM.