Wubbel Catherine, Asmus Michael J, Stevens Gary, Chesrown Sarah E, Hendeles Leslie
Pulmonary Division, Department of Pediatrics, College of Medicine, University of Florida, Gainesville, FL, USA.
Chest. 2004 Feb;125(2):453-8. doi: 10.1378/chest.125.2.453.
Recent American Thoracic Society guidelines recommend two different methods of methacholine challenge testing: the 2-min tidal breathing method with twofold increases in concentration, and the five-breath dosimeter method with fourfold increases. Since the tidal breathing method delivers more methacholine to the mouthpiece, we hypothesized that the provocative concentration of methacholine required to decrease FEV(1) by 20% (PC(20)) would be lower than with the dosimeter method.
Twelve subjects 18 to 45 years old with stable asthma were selected on the basis of a screening PC(20) (by tidal breathing) of < 1 mg/mL, 1 to 4 mg/mL, or 4 to 16 mg/mL (4 subjects in each concentration range). On subsequent visits within a 7-day period, methacholine challenge testing with tidal breathing or dosimeter were performed on separate days, in a randomized crossover manner.
The geometric mean PC(20) was 1.8 mg/mL (95% confidence interval [CI], 0.7 to 4.3) after tidal breathing and 1.6 mg/mL (95% CI, 0.7 to 3.7) after dosimeter (p = 0.2). There was no significant difference between the screening PC(20) and the PC(20) obtained by either method on randomized study days. The maximum decrease in FEV(1) from diluent baseline after the last concentration was 27.8% (range, 20 to 50%) during tidal breathing and 27.9% (range, 16 to 47%) during the dosimeter method (p = 0.35).
Both methods give similar results. Fourfold increases in methacholine concentration with the dosimeter method are as safe as twofold increases with the tidal breathing method.
美国胸科学会近期发布的指南推荐了两种不同的乙酰甲胆碱激发试验方法：浓度加倍的2分钟潮气呼吸法和浓度四倍递增的五次呼吸剂量仪法。由于潮气呼吸法会向咬嘴输送更多的乙酰甲胆碱，我们推测使第一秒用力呼气容积（FEV₁）降低20%所需的乙酰甲胆碱激发浓度（PC₂₀）会低于剂量仪法。
选取12名年龄在18至45岁之间的稳定期哮喘患者，筛选时依据潮气呼吸法测得的PC₂₀分为<1mg/mL、1至4mg/mL或4至16mg/mL三个浓度范围（每个浓度范围4名受试者）。在7天内的后续访视中，以随机交叉方式在不同日期分别采用潮气呼吸法或剂量仪法进行乙酰甲胆碱激发试验。
潮气呼吸法后的PC₂₀几何均值为1.8mg/mL（95%置信区间[CI]，0.7至4.3），剂量仪法后的PC₂₀几何均值为1.6mg/mL（95%CI，0.7至3.7）（p = 0.2）。在随机研究日，筛选时的PC₂₀与两种方法测得的PC₂₀之间无显著差异。末次浓度后，潮气呼吸法中FEV₁相对于稀释剂基线的最大降幅为27.8%（范围20%至50%），剂量仪法中为27.9%（范围16%至47%）（p = 0.35）。
两种方法结果相似。剂量仪法中乙酰甲胆碱浓度四倍递增与潮气呼吸法中浓度加倍一样安全。
