Intrapulmonary bronchi in excised dog lungs were outlined with tantalum dust and stereoscopic radiographs taken during deflation and inflation of the lung after rinsing with solutions of saline, histamine, isoprenaline or EDTA. Dimensions of airways were calculated from measurements of the stereoscopic X-ray images. 2. After treatment with EDTA to minimize bronchial smooth muscle activity, airway diameters increased at all transpulmonary pressures (Ptp) and lung volumes relative to their diameter after treatment with histamine; airway hysteresis in relation to Ptp decreased. 3. At low lung volumes, the per cent increase from histamine to EDTA for airways of different sizes was the same (24-30%) but at high volumes (30 cm H2O distending pressure) the dilatation induced by EDTA was 30% for airways less than 3.0 mm diameter and 13% for those greater than 5.0 mm diameter. 4. Even at high lung volumes, intrapulmonary airways are free to constrict or dilate in spite of the stiffness of the supporting parenchyma.
摘要
用钽粉勾勒出切除的犬肺内支气管轮廓，在用盐水、组胺、异丙肾上腺素或乙二胺四乙酸（EDTA）溶液冲洗后，在肺萎陷和膨胀过程中拍摄立体X线片。根据立体X线图像的测量结果计算气道尺寸。2. 用EDTA处理以尽量减少支气管平滑肌活动后，在所有跨肺压（Ptp）和肺容积下，气道直径相对于用组胺处理后的直径均增加；与Ptp相关的气道滞后现象减少。3. 在低肺容积时，不同大小气道从组胺处理到EDTA处理的直径增加百分比相同（24% - 30%），但在高肺容积时（扩张压力为30 cm H₂O），EDTA对直径小于3.0 mm的气道诱导的扩张为30%，对直径大于5.0 mm的气道为13%。4. 即使在高肺容积时，尽管支持性实质组织僵硬，但肺内气道仍可自由收缩或扩张。
