Effect of Pulmonary Blood Flow upon Lung Mechanics*

Abstract

Abstract. Airway pressure was continuously recorded in an isolated horizontally mounted canine heart-lung preparation during abrupt, stepwise 100-200 ml inflations to 20-25 cm water pressure, and subsequent deflations. With each change in volume there was a steep rise or fall in pressure, followed by stress relaxation to a static equilibrium airway pressure. Comparison was made between the nonperfused state and during perfusion with whole blood at 100 ml/kg dog wt per min, and left atrial pressure of 10 mm Hg. Pressure tracings were similar during deflation in the perfused and the nonperfused lung. During inflation, in the middle range of lung inflation volumes, the peak inflation and equilibrium airway pressures were greater in the nonperfused state; maximum difference of static pressures in nine preparations averaged 146% of perfused values and the average stress relaxation difference from eight of these was 276%. Lung distensibility was the same with packed red cells or plasma perfusates and was not changed by varying the perfusion rate up to 220 ml/kg per min. During cyclic ventilation, dynamic compliance was similarly greater in the perfused than in the nonperfused state in the middle range of inflation volumes. Static distention of the vascular bed produced similar results with progressive improvement in distensibility in midinflation range up to a hydrostatic pressure of 15 cm blood. These data suggest that the distended pulmonary vascular bed provides structural airway support which facilitates entry of gas diminished pressure. IntroductionThe influence of the pulmonary vascular bed upon pulmonary mechanics is not clear. Basch, in 1887, suggested that perfusion of the pulmonary capillaries under normal conditions serves to maintain alveolar distention (1). Other investigators

Mechanostructural adaptations preceding postpneumonectomy lung growth

“…We did not separately manipulate the potential components of lung impedance; namely, the amount of lung tissue and pulmonary blood flow. Based on this study and prior work [40], we anticipate that lung volume and blood volume will have reciprocal influences on tissue resistance.…”

The Cardiorespiratory Effects of Haemorrhage and Overtransfusion in Dogs

“…The third possibility is that the reduction in pulmonary blood flow might have affected the pulmonary vascular bed in such a way that it weakened the structural support of the lung. The suggestion that the distended pulmonary vascular bed provides structural airway support has been made by Giannelli, Ayres and Buehler (1967) on the basis of studies in the isolated, perfused and ventilated lung, but there is as yet no confirmatory evidence that such a mechanism is of importance in the intact animal.…”

Structural and functional evidence for the scaffolding effect of alveolar blood vessels

“…Borst et al localized the vascular effect to the alveolar capillaries or pulmonary veins by observing that lung compliance changed with increased left atrial pressures, but did not change over a wide range of pulmonary artery pressures [20]. Similarly, the rapid reversibility of the scaffold effect [4, 20] suggested that the blood volume contribution was related to structural distension of alveolar capillaries and not an indirect effect on tissue composition or surfactant function. In the present study, we provided additional functional evidence, based on lung impedence studies, for the scaffold effect of pulmonary blood flow.…”

“…Frank and co-workers showed that vascular distension increased lung volumes at a given applied pressure [3]. Gianelli et al used the word “scaffolding” to describe the effect of perfusion on lung mechanics in an isolated dog heart-lung preparation [4]. In addition to confirming the improved compliance at mid-lung volumes, Giannelli et al noted that the vascular effect was observed irrespective of flow; the scaffolding effect was observed with both static distension and active perfusion.…”