Twentyman O P, Hood S V, Holgate S T
University of Southampton, Southampton General Hospital, United Kingdom.
J Appl Physiol (1985). 1993 Jun;74(6):3034-9. doi: 10.1152/jappl.1993.74.6.3034.
Considerable controversy exists over the influence of baseline airway caliber on indexes of bronchial responsiveness in asthma. To directly investigate this, we used inhaled methacholine to alter baseline airway caliber to determine whether this altered the airway response to subsequent bronchoprovocation with inhaled histamine. Seventeen stable asthmatic subjects were studied; their median age was 22 yr, baseline forced expiratory volume in 1 s (FEV1) was 101.5 +/- 3.7% (SE) predicted, and geometric mean provocative concentration of inhaled methacholine causing a 20% fall in FEV1 (PC20) was 0.87 mg/ml. Initially the time course of bronchoconstriction to inhaled methacholine was determined. Subsequently the airway response to inhaled histamine administered as a single concentration was determined, both before and after reductions in baseline FEV1 by saline or methacholine of 0, 15, 25, and 35%, on 4 separate days. Altering baseline airway caliber had no effect on the subsequent response of the airways to inhaled histamine when calculated as percent fall from the new baseline. The power of the study to detect an effect of altering baseline FEV1 on the measured PC20 histamine of 0.5 doubling dilutions was > 55%, and the power to detect an effect of 1.0 doubling dilutions was > 98%.
关于基线气道口径对哮喘患者支气管反应性指标的影响存在相当大的争议。为了直接研究这一问题，我们使用吸入乙酰甲胆碱来改变基线气道口径，以确定这是否会改变气道对随后吸入组胺激发试验的反应。对17名病情稳定的哮喘患者进行了研究；他们的年龄中位数为22岁，基线第1秒用力呼气量（FEV1）为预测值的101.5±3.7%（标准误），引起FEV1下降20%的吸入乙酰甲胆碱的几何平均激发浓度（PC20）为0.87mg/ml。首先确定了对吸入乙酰甲胆碱的支气管收缩时间过程。随后，在4个不同的日子里，分别在基线FEV1用生理盐水或乙酰甲胆碱降低0%、15%、25%和35%之前和之后，测定了对单一浓度吸入组胺的气道反应。当以相对于新基线的下降百分比计算时，改变基线气道口径对气道随后对吸入组胺的反应没有影响。该研究检测基线FEV1改变对组胺PC20测量值产生0.5倍稀释倍数影响的效能>55%，检测1.0倍稀释倍数影响的效能>98%。
