DISTURBANCE OF ALVEOLAR LINING LAYER - EFFECTS ON ALVEOLAR MICROSTRUCTURE

To further study the influence of altered surface tensions on alveolar micromechanics, we analyzed the structure-function relationships in e xcised rabbit lungs filled with or rinsed by a fluorocarbon (similar t o 15 mN/m) or by hexadecane (similar to 25 mN/m). The lungs were fixed and dehydrated by vascular perfusion, and the tissue samples were ana lyzed by light, transmission, and scanning electron microscopy. We mad e three observations. 1) Pressure-volume (P-V) loops of hexadecane-fil led lungs are shifted to the left and coincide with those of saline-fi lled lungs, indicating near-zero interfacial tension. In accordance, t he alveolar microstructure and surface area of hexadecane-filled lungs resemble those of saline-filled lungs. 2) The P-V loops of fluorocarb on-filled lungs are not shifted to the left but coincide with those of fluorocarbon-rinsed lungs. Under both conditions, the alveolar micros tructure is qualitatively identical and the alveolar surface areas are markedly reduced compared with normal air-filled lungs. These finding s show that fluorocarbon-filled or fluorocarbon-rinsed lungs are subje cted to similar interfacial tensions at the alveolar level. 3) Hexadec ane-rinsed lungs show a pear-shaped P-V curve and a complex surface te xture of peripheral air spaces. These results, together with in vitro observations, suggest a metamorphic interplay between lung surfactant and hexadecane in lining the surface and determining the surface tensi on. Evidently, the effects of foreign liquids introduced into the lung on the structure-function relationship cannot accurately be predicted from their in vitro surface tensions. This fact should be considered in the development of artificial surfactants.