Morrell N W, Roberts C M, Biggs T, Seed W A
Department of Medicine, Charing Cross and Westminster Medical School, London, United Kingdom.
Am Rev Respir Dis. 1993 Mar;147(3):535-9. doi: 10.1164/ajrccm/147.3.535.
The effectiveness of collateral ventilation in maintaining alveolar gas tensions in obstructed lung segments was investigated using fiberoptic bronchoscopy to place an occluding catheter-tip balloon in selected lobar and segmental bronchi in supine normal human subjects. Gas tensions from beyond the occlusion were measured with a respiratory mass spectrometer. Collateral ventilation is known to be minimal between lobes; therefore, values measured in obstructed lobes provide a control. No significant difference was found between the partial pressures of oxygen or carbon dioxide measured in obstructed lobes and in obstructed segments. In both cases respiratory gas tensions approached reported values for mixed venous levels. The time taken to attain a steady state of gas composition in the obstructed lung was rapid (approximately 50 s), and it was no different for lobes and segments. In addition, collateral ventilation was assessed by measuring the amount of helium reaching occluded lobes and segments when subjects breathed a mixture of 21% oxygen and 79% helium. The rate of rise in helium concentration was less than 1%/min in both lobes and segments, a figure that may be explained by delivery of helium in recirculated blood rather than by collateral ventilation. We conclude that intersegmental collateral ventilation has a negligible role in the maintenance of alveolar gas tensions in supine normal humans during tidal breathing.
利用纤维支气管镜在仰卧位正常人体受试者的选定叶支气管和段支气管中放置阻塞性导管尖端球囊，研究侧支通气在维持阻塞肺段肺泡气体张力方面的有效性。用呼吸质谱仪测量阻塞部位远端的气体张力。已知叶间的侧支通气极少；因此，在阻塞肺叶中测得的值可作为对照。在阻塞肺叶和阻塞肺段中测得的氧分压或二氧化碳分压之间未发现显著差异。在这两种情况下，呼吸气体张力均接近混合静脉血水平的报告值。阻塞肺达到气体成分稳定状态所需的时间很快（约50秒），肺叶和肺段之间没有差异。此外，当受试者吸入21%氧气和79%氦气的混合气体时，通过测量到达阻塞肺叶和肺段的氦气量来评估侧支通气。肺叶和肺段中氦浓度升高的速率均小于1%/分钟，这一数值可能是由于再循环血液中氦的输送而非侧支通气所致。我们得出结论，在仰卧位正常人体潮式呼吸过程中，段间侧支通气在维持肺泡气体张力方面的作用可忽略不计。
