Willet K E, Gurrin L, Burton P, Lanteri C J, Reese A C, Vij J, Matsumoto I, Jobe A H, Ikegami M, Polk D, Newnham J, Kohan R, Kelly R, Sly P D
Division of Clinical Sciences, Institute for Child Health Research, West Perth, Australia.
Respir Physiol. 1996 Mar;103(3):271-80. doi: 10.1016/0034-5687(95)00095-x.
A single combined intramuscular dose of betamethasone and l-thyroxine (T4) or placebo was injected into the shoulder of fetal lambs 48 hours prior to delivery at days 121 (n = 14), 128 (n = 25) or 135 (n = 20) of gestation. Respiratory mechanics were calculated using multiple linear regression analysis. Both respiratory system resistance (RRS) and elastance (ERS) decreased approximately 4 fold between gestational days 121 (D121) and 135 (D135). Both variables were also reduced by hormone treatment. Reduction in ERS was due to a reduction in both lung (EL) and chest wall (EW) components. In absolute terms EW decreased with gestational age; however, EW as a proportion of total elastance (% EW) increased. Inclusion of a volume-dependent elastance term in the multiple linear regression model enabled us to separate total elastance into volume-independent (E1) and volume-dependent (E2V) components. E1 decreased almost 8-fold compared with only a 2.5-fold fall in E2V between D121 and D135. %E2, the proportion of ERS which is volume-dependent and which provides an index of overventilation, doubled over this time period. Hormone treatment affected E1 and E2V components equally hence %E2 was not altered. Both excised lung volume and end expiratory alveolar volume increased with gestational age and with treatment. The response to treatment was qualitatively similar at each of the gestational ages examined, however, for all mechanics variables, except resistance and E1, the magnitude of response to treatment was significantly smaller in D135 animals compared with other age groups.
在妊娠第121天（n = 14）、128天（n = 25）或135天（n = 20）分娩前48小时，向胎羊肩部单次肌内注射倍他米松和左旋甲状腺素（T4）联合制剂或安慰剂。使用多元线性回归分析计算呼吸力学参数。在妊娠第121天（D121）至135天（D135）期间，呼吸系统阻力（RRS）和弹性（ERS）均下降了约4倍。激素治疗也使这两个变量降低。ERS的降低是由于肺（EL）和胸壁（EW）成分均减少。从绝对值来看，EW随胎龄增加而降低；然而，EW占总弹性的比例（%EW）却增加了。在多元线性回归模型中纳入与容积相关的弹性项，使我们能够将总弹性分为与容积无关的（E1）和与容积相关的（E2V）成分。与D121至D135期间E2V仅下降2.5倍相比，E1下降了近8倍。%E2是ERS中与容积相关的比例，可作为过度通气的指标，在此时间段内增加了一倍。激素治疗对E1和E2V成分的影响相同，因此%E2未改变。切除的肺容积和呼气末肺泡容积均随胎龄和治疗而增加。在所检查的每个胎龄，对治疗的反应在性质上相似，然而，对于所有力学变量，除了阻力和E1，D135组动物对治疗的反应幅度与其他年龄组相比明显较小。
