Distribution of blood flow in isolated lung; relation to vascular and alveolar pressures

TLDR

Pulmonary blood flow is governed by hydrostatic effects and Starling resistance. The study employed an isolated dog left lung ventilated with negative pressure and perfused with venous blood, varied pulmonary arterial, venous, and alveolar pressures, and measured flow distribution using Xe133. Flow was absent above the alveolar–arterial pressure equality level, increased linearly below it at low venous pressure, became more uniform when venous pressure rose, and could be fully explained by Starling‑type vessel resistance, enabling simulation of human flow patterns.

Abstract

The left lung from a dog was removed, ventilated with negative pressure, and perfused with venous blood. Pulmonary arterial, venous, and alveolar pressures could be varied over a large range. The distribution of blood flow in the lung was measured with Xe 133 . Under these conditions, there was no blood flow above the level at which alveolar equaled arterial pressure (measured at the arterial cannula). Below this level there was a linear increase in blood flow down the lung when the venous pressure was kept low. Raising the venous pressure made the distribution of flow more uniform below the level at which venous and alveolar pressures were equal although flow still increased down this zone. The flow distribution could be completely accounted for by the mechanical effects of the pressure inside and outside the blood vessels which each behaved like a Starling resistance. It was possible to simulate the flow distributions found in man in various physiological and diseased states. pulmonary; hydrostatic effect; Starling resistance Submitted on November 15, 1963