Meyer M, Hook C, Rieke H, Piiper J
J Appl Physiol Respir Environ Exerc Physiol. 1983 Dec;55(6):1795-802. doi: 10.1152/jappl.1983.55.6.1795.
Simultaneously measured helium (He) and sulfur hexafluoride (SF6) single-breath washout was studied in 16 anesthetized paralyzed dogs ventilated with a special hydraulically operated ventilatory servo system. After equilibration of lung gas with 1% He and 1% SF6, the maneuver consisting of inspiration of a test gas-free mixture at constant rate (VI), a variable time of breath holding, and an expiration at constant rate (VE), was performed. Fractional concentrations of He and SF6, recorded against expired volume, were analyzed in terms of slope of the alveolar plateau (S) and series (Fowler) dead space (VD). In control conditions (VI = 0.5 l/s, VE = 0.1 l/s) S was about 10% of alveolar-to-inspired concentration difference per liter expirate both for He and SF6. Both SHe and SSF6 were inversely related to VI and VE, the relative changes being more pronounced with varying VE. SHe/SSF6 was higher or lower than unity depending on VI and VE. Both SHe and SSF6 decreased with increasing preinspiratory lung volume. Breath holding up to 10 s slightly decreased SHe and SSF6 while SHe/SSF6 was unchanged. The contribution of continuing gas exchange to S assessed from comparative measurements using the reversed (single breath washin) technique ranged from 6 to 23% in the various conditions. The VDHe/VDSF6 ratio was 0.84 and was little affected in the various settings. Results indicate that the substantial alveolar gas inhomogeneity in the dog lung and the mechanism accounting for S are little diffusion dependent. By exclusion sequential filling and emptying of lung units is believed to constitute the most important mechanism responsible for the sloping alveolar plateau.
在16只使用特殊液压操作通气伺服系统进行通气的麻醉瘫痪犬中，研究了同时测量的氦气（He）和六氟化硫（SF6）单次呼吸洗脱。在用1% He和1% SF6平衡肺内气体后，进行了以下操作：以恒定速率（VI）吸入无测试气体的混合物、可变的屏气时间以及以恒定速率（VE）呼气。根据肺泡平台斜率（S）和系列（Fowler）死腔（VD）分析记录的He和SF6相对于呼出体积的分数浓度。在对照条件下（VI = 0.5 l/s，VE = 0.1 l/s），He和SF6的S约为每升呼出气体中肺泡与吸入浓度差的10%。SHe和SSF6均与VI和VE呈负相关，随着VE的变化，相对变化更为明显。SHe/SSF6高于或低于1，具体取决于VI和VE。SHe和SSF6均随着吸气前肺容积的增加而降低。屏气长达10秒会使SHe和SSF6略有降低，而SHe/SSF6不变。使用反向（单次呼吸吸入）技术通过比较测量评估的持续气体交换对S的贡献在各种条件下为6%至23%。VDHe/VDSF6比值为0.84，在各种设置下受影响较小。结果表明，犬肺中存在大量肺泡气体不均匀性，且解释S的机制几乎不依赖于扩散。通过排除法，肺单位的顺序填充和排空被认为是导致肺泡平台倾斜的最重要机制。
