Saline-filled Lungs Research Articles

Effects of a molecular change in collagen on lung structure and mechanical function.

Semicarbazide, a lathyrogen, was given to growing rats to elucidate the consequences of altering the molecular structure of fibrous proteins within the lung. Static pressure-volume (P-V) measurements during deflation of saline-filled lungs showed normal recoil pressure and compliance values within the physiological range of lung volume. Quasi-static P-V measurements were also normal during slow reinflation, even beyond physiological limits to a recoil pressure of 20 cm H20. However, the lungs of experimental rats ruptured at much lower recoil pressures than controls. Histology was normal in lungs fixed at 20 cm H20. In contrast, lungs showed dilation of terminal air spaces, rupture of alveolar walls, and an increase in mean linear intercept in experimental compared with control specimens, when fixed at 30 cm H20. Biochemical analyses revealed reduced cross-linking of lung collagen without change in its total content. There were no detectable changes in the quantity or quality of lung elastin. It is concluded that semicarbazide may selectively impair the maturation of lung collagen and that immaturity of lung collagen is associated with a reduction in the tensile strength of lung tissue, without changes in elasticity within physiological volume limits.

Vertical gradients of pleural and transpulmonary pressure with liquid-filled lungs

In supine dogs with saline-filled lungs the vertical gradient of pleural surface pressure (VGPpI) was not significantly different from −1 cm H 2O/cm and that of transpulmonary pressure (VGPtp) was not significantly different from zero. Hence the hydrostatic gradient of the liquid was entirely taken up by the chest wall, the ribs being rigid in the direction of gravity and the diaphragm facing an equal hydrostatic gradient on both sides. In head-up dogs VGPpI was −0.8 cm H 2O/cm when the level of the liquid in the filling system was 19.5 cm below the lung top and −0.5 cm H 2O/cm when this level corresponded to the top. The hydrostatic gradient of the liquid was not entirely taken up by the rib cage because of its uneven regional compliance and VGPtp was reversed with respect to that of the air-filled lung. With fluorocarbon (specific gravity 1.75) filled lungs in the supine posture VGPpI was about −1.28 cm H 2O/cm and VGPtp was reversed. In the head-up posture VGPpI was about −1.2 cm H 2O/cm and VGPpt was reversed.

Gas exchange in saline-filled lungs of man.

Gas exchange in saline-filled lungs of man.

The effect of vitamin A deficiency in rabbits on the elastic properties of the lung and thoracic aorta.

Weanling rabbits were fed a vitamin A deficient diet for 6 weeks. During this period they failed to gain weight normally and exhibited significantly lower serum vitamin A levels when compared with their littermates fed a vitamin A supplemented diet. These findings indicated that vitamin A deficiency was established, and the lungs and specimens of aorta were removed for study. The pressure–volume relationships of saline-filled lungs revealed that test lungs were more compliant than control lungs and this difference was associated with a decrease in elastin content in test lungs. The absence of such changes in pair-fed controls suggests that the effects are due to vitamin A deficiency per se rather than the general effects of retarded growth. A decrease was also noted in the elastance of the aorta, confirming that vitamin A deficiency has an effect on elasticity of tissues generally. When vitamin A deficient animals were given vitamin A supplemented diets the elastance of the aorta returned to control values but the compliance of the lung, although somewhat decreased, did not reach control values. The mechanism by which vitamin A deficiency affects tissue elasticity is not known.

Distribution of blood flow and ventilation in saline-filled lung

The airways of degassed greyhound lungs were filled with saline and the lung suspended in a saline bath and perfused with blood. The distribution of blood flow was measured by injecting aggregated I131-labeled albumin into the pulmonary artery and scanning the lung from bottom to top when the particles had been trapped by the small vessels. After equilibrating the alveolar saline with more inhaled iodinated albumin and scanning again, blood flow per unit alveolar volume could be calculated. With vascular pressures which have been shown to cause great topographical inequality of blood flow in the gas-filled lung, blood flow was evenly distributed on the average in the saline-filled preparation, presumably because the hydrostatic pressures difference in the blood vessels were balanced by corresponding pressures in the airways. The topographical distribution of a single breath of iodinated albumin in saline was found to be uniform but there was striking stratified inhomogeneity along the airways. This was due to the slow diffusion rate of albumin in saline and similar effects were seen with inhaled radioactive oxygen and carbon dioxide dissolved in saline. The results show that when the mammalian lung breathes saline, diffusion limitations for oxygen and carbon dioxide within the airways may be an important factor. aerosols; hydrostatic pressures; increased acceleration; airways diffusion; topographical differences; gas exchange; pressure-flow relations Submitted on March 18, 1965

Surface tension of alveolar lining of non-atelectatic rat lungs

The volumes of fully inflated, isolated rat lungs were measured by keeping their dimensions constant while injecting air into them and applying Boyle's law. The lungs were then emptied gradually and pressure volume curves were constructed using the measured volumes. The pressures developed by the alveolar surface were calculated by using these curves of air-filled lungs and curves obtained from saline-filled lungs of comparable animals. These pressures were less than similar pressures previously obtained from rat lungs filled from the atelectatic state. These results support the suggestion that the process of making lungs atelectatic decreases the efficacy of the surface active material of the alveolar lining.

Static volumepressure interrelations of the lungs and pulmonary blood vessels in excised cats' lungs.

Measurements were made of the effect of pulmonary vascular distention on static volume-pressure relations of excised cats' lungs filled either with saline to minimize surface forces, or inflated with gas. Only slight changes of questionable significance occurred in elastic behavior of the lungs during deflation when pulmonary vascular pressure was increased from 0 to 16 cm H2O. Measurements were also made of quasi-static pulmonary vascular volume-pressure relations at different lung volumes. The overall slope of the vascular volume-pressure curve in saline-filled lungs was greatest at a moderate lung volume and was slightly less when the lungs were either collapsed or highly distended. The vascular volume-pressure curve was considerably flattened in gas-inflated lungs at airway pressures above 10 cm H2O. During filling and emptying of the vascular system there were slight but definite changes in equilibrium volume of the lung. Hysteresis of the vascular system was an invariable finding. Regardless of the complex mechanism underlying hysteresis, it can be explained if all units of the system are assumed to have sigmoid volume-pressure curves. The findings of these experiments illustrate the highly complex interrelations of the pulmonary blood vessels and lungs, particularly when surface forces are taken into account. Note: (With the Technical Assistance of Martha McLaughlin) Submitted on May 29, 1958