Macfie A E, Harris E A, Whitlock R M
J Appl Physiol Respir Environ Exerc Physiol. 1979 Feb;46(2):263-7. doi: 10.1152/jappl.1979.46.2.263.
Mean transit time (MTT), coefficient of variation (COV), and index of skewness (IOS) of transit times were measured, with the more conventional derivatives of the forced expiratory spirogram, in 178 healthy people aged 6-71 yr breathing air, and in 18 healthy adults breathing 20% oxygen in helium (O2He) in addition. Breathing O2He very significantly altered MTT and all derivatives with dimensions of flow or time, but altered COV and IOS very little. Between 6 and 30 yr mean MTT, after adjustment for expired volume, remained constant and then increased to 71 yr. Mean COV and IOS increased from 6 to 71 yr, though with an apparent change in rate during the early teens. The results suggest that whereas the resistance of large airways falls in proportion to growth of the lungs, small-airway resistance becomes less uniform during both childhood and adult life.
对178名年龄在6至71岁、呼吸空气的健康人，以及另外18名呼吸含20%氧气的氦气（O₂He）的健康成年人，测量了转运时间的平均转运时间（MTT）、变异系数（COV）和偏度指数（IOS），同时还测量了用力呼气肺量图的一些更传统的衍生指标。呼吸O₂He会非常显著地改变MTT以及所有具有流量或时间维度的衍生指标，但对COV和IOS的改变很小。在6至30岁之间，经呼气量校正后的平均MTT保持恒定，然后在71岁时增加。平均COV和IOS从6岁到71岁增加，尽管在青少年早期速率有明显变化。结果表明，虽然大气道阻力随肺部生长成比例下降，但小气道阻力在儿童期和成年期变得不那么均匀。
