The significance of alterations in the lung arterial pattern.

Abstract

Aknowledge of the arterial blood supply to the lungs, which can be determined by standard radiographic methods, may be helpful in establishing their physiologic status. Classical pulmonary function tests, such as the determination of vital capacity, maximal breathing capacity, and timed vital capacity, only measure ventilation; they do not evaluate perfusion of the lungs. A localized deficiency in ventilation is measured only as a total deficit in function by these methods unless a complicated technic such as bronchospirometry is used. The information about the lung circulation which is obtained by the radiographic procedures to be described, interpreted on the basis of well accepted pathophysiologic data, will aid in the evaluation of pulmonary abnormalities and in the selection of patients for surgical treatment. Material In order to demonstrate the clinical usefulness of such information, venous and aortic angiography was performed in dogs after the pattern of blood supply to the lungs had been altered in three ways: 1. By transection and suture of a main bronchus (Fig. 1), which has been shown to diminish the pulmonary artery blood supply to the atelectatic lung without any increase in the bronchial collateral circulation(1). When studies were completed at this stage, some of the animals were operated on a second time and the transected bronchus was anastomosed; this was done twelve to twenty-four months after the initial transection. 2. By ligation of a main pulmonary artery, which leads to the development of extensive bronchial arterial collateral circulation. 3. By anastomosis of the left subclavian artery to the pulmonary artery (Blalock procedure) (Fig. 2). This simulates the pulmonary plethora seen with left-to-right shunts and provides an easily demonstrable systemic-pulmonary artery anastomosis. After completion of the radiographic studies, autopsies were performed on some of the animals, followed by plastic and barium injection studies, in order to verify anatomically the impressions gained from the films. Radiologic Findings In animals in which a bronchus had been transected, there was a prompt collapse of the lung, accompanied by a shift of the mediastinum toward that side. This was associated with increased expansion of the normal lung, which soon became distended enough to occupy almost all of the chest. Aortograms revealed no filling of the bronchial arteries on either side under these conditions of chronic atelectasis (Fig. 3). Venous angiography (Fig. 4, A) provided good visualization of the pulmonary arteries on the unoperated side of the chest. In addition, these vessels were two or three times larger than normal and were widely spread, as would be expected from the compensatory overexpansion of the normal lung.