Abstract
The purpose of this study was to elucidate whether or not the reduction of lung volume is related to the mechanism of blood flow reduction in the atelectatic lung. In adult mongrel dogs, whose main stem bronchus in the thoracotomized lung was obstructed, the change of blood flow in the lung containing N2 was compared with that in the collapsed lung.
1) Under a low partial pressure of O2 in the broncho-alveolar system by obstruction of the main stem bronchus, the blood flow did not change, even when the N2 volume in the lung was varied. Therefore, the change of blood flow in the collapsed lung is not attributable to the reduction of lung volume.
2) The lung blood flow increased when the partial pressure of O2 in the broncho-alveolar system was elevated by infusion of O2 into the collapsed lung, and it decreased with the subsequent O2 absorption leading to lung collapse. Therefore, the change of lung blood flow is due to the change of intraalveolar partial pressure of O2.
3) The reduction of blood flow in the atelectatic lung is caused by hypoxic pulmonary vasoconstriction, and is not influenced by the reduction of lung volume due to the lung collapse.
