Source: Annual Congress 2002 - Lung mechanics: from laboratory to bedside
Disease area: Interstitial lung diseases

Abstract

Changes in pulmonary haemodynamics alter lung mechanics; however, the role of pulmonary microcirculation in maintaining normal volume-dependent behaviour of the lung has not yet been characterised. Pulmonary input impedance (ZL) was measured in three groups of isolated rat lungs at both increasing and decreasing mean traspulmonary pressures (Ptpmean) of 1, 2, 4, 6 and 8 cmH2O. Lungs were either unperfused (n = 7), or they were perfused with either blood (n = 7) or 8% albumin (n = 7) while physiological pulmonary hemodynamical parameters were maintained. Airway resistance (Raw), parenchymal damping (G), elastance (H) were estimated from ZL spectra under each condition. Increasing Ptpmean resulted in monotonous decreases in Raw with no difference between the groups. G and H were minimal at Ptpmean = 4-6 cmH2O and were significantly greater at both lower and higher pressures. Pulmonary perfusion affected the volume-dependent behaviour of the lungs: G and H were significantly greater in the unperfused lungs than those perfused with either perfusate at Ptpmean levels lower than 6 cmH2O, whereas no difference was observed between the groups at higher Ptpmean. These results suggest that, at low and moderate lung volumes, pulmonary perfusion improves the parenchymal viscoelasticity via optimising the alveolar wall structure. The role of the filled microcirculation becomes less significant compared to that of the distending elastic forces at high transpulmonary pressures. Therefore, at lung volumes around or lower than FRC, pulmonary perfusion is fundamental in stabilising the connective tissue fiber skeleton, which results in an improvement in the viscoelastic properties of the parenchyma.
Supported by OTKA T30670 and SNSF 064899.01/1

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Citations should be made in the following way:
F. Petak, B. Babik, Z. Hantos, D. R. Morel, J. C. Pache, W. Habre (Szeged, Hungary; Geneva, Switzerland). The effects of pulmonary circulation on the volume-dependent behaviour of the lungs. Eur Respir J 2002; 20: Suppl. 38, 184

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