Hypoxic bronchodilation

Recent advances in computed tomographic imaging provide a unique method to serially and directly visualize acute physiological responses in the lung. To directly investigate the airway response to hypoxia, high-resolution computed tomographic scans of the lungs of eight intact anesthetized minipigs were serially repeated before, during, and after ventilation with a hypoxic gas mixture (inspired fraction of O₂ ≃ 0.07). This approach demonstrated an acute reversible 56 ± 8% (SE) dilation in large airways (>2 mm diam) and a 90 ± 15% dilation in small airways (<1.99 mm diam) with decreased inspired O₂ tension. Of the airways studied, 70 of 76 dilated. Hypoxic bronchodilation may interact with hypoxic pulmonary vasoconstriction in the fundamental physiological process of ventilation-perfusion matching in the lung.