342例健康幼儿弦线和比时间常数初探

A Preliminary Study of the Chord and Specific Time Constants in 342 Healthy Children

在所测3～6岁健康幼儿342名的MEFV曲线上,取V_(75)、V_(50)、V_(25)的数据,用Knud-son的弦线法计算高、中、低肺容积处的弦线时间常数(τ_(ch)),τ_(ch75)、τ_(ch50)、τ_(ch25)和比时间常数(Sτ),1/V_(75)、1/V_(50)、1/V_(25)。结果表明,将τ_(ch)用容积校正后的Sτ,较τ_(ch)更能精确反映某肺容积处单位容积改变时所需的时间;各Sτ随年龄的增长而缩短,反映幼儿期间肺弹性回缩压(P_(Lel))和气道传导率(G_(aw))随年龄增长而加大;Sτ随肺内容积衰减而下降,反映P_(Lel)和G_(aw)随肺内容积衰减而下降;而τ_(ch)未见任何规律性改变,可能与影响τ_(ch)的因素较为复杂有关。

Using Knudson's method,the chord time constant, τ_(ch), τ_(ch75), τ_(ch50),τ_(ch25), and specific time constant, Sτ, 1/Ⅴ_(75), 1/Ⅴ_(50), 1/Ⅴ_(25), at high, middle andlow lung volumes were calculated fromⅤ_(75), Ⅴ_(50) and Ⅴ_(25) of the MEFV curvesmeasured previously from 342 healthy chil-dren of 3-6 years of age in a nursery.The multiple stepwise regression equationwere built with age, height and FVC asindependent variables by the IBM-XT/PCcomputer. The result showed that the Sτcorrected by volume from τ_(ch) could reflectthe time required for change of unit lungvolume more precisely than τ_(ch) owing tothe elimination of the influence of lung volume. The Sτ was shortened with theincrease of age, and was negatively corre-lated with age and FVC. These facts re-fl_e. cted the growth of lung elastic pressure(P_(Lel)) and airway conductance (Gaw)with the increase of age. The prolongationof Sτ with the decay of lung volume justreflected the decrease of P_(Lel) and G_(aw) withthe decay of lung volume. No regularchanges of τ_h were observed with age andlung volume. Probably, it was concernedwith the complexity of factors affectingthe τ_(ch).