Cockcroft Donald W, Davis Beth E, Todd David C, Smycniuk Audrey J
Division of Respiratory Medicine, Department of Medicine, Royal University Hospital, University of Saskatchewan, Ellis Hall, Fifth Floor, Saskatoon, SK, S7N 0W8 Canada.
Chest. 2005 Mar;127(3):839-44. doi: 10.1378/chest.127.3.839.
Guidelines for the 2-min tidal-breathing and the five-breath dosimeter methods for methacholine challenge have recently been published by the American Thoracic Society (ATS). Although subjects are exposed to twice as much aerosol at any given concentration during the tidal-breathing method compared to the dosimeter method, they were thought to give equivalent results.
To compare the 2-min tidal-breathing and the five-breath dosimeter methacholine challenges.
Tertiary care university-based bronchoprovocation laboratory.
Forty subjects with currently symptomatic asthma.
The two methacholine tests were done in random order on separate days at the same time of day at 1- to 7-day intervals.
The dosimeter provocation concentration of methacholine causing a 20% fall in FEV(1) (PC(20)) was almost twice that of the tidal-breathing PC(20): 2.4 mg/mL vs 1.3 mg/mL (paired t test, p < 0.00005). The difference was greater in those with mild airway hyperresponsiveness (AHR) [PC(20) > 1.0 mg/mL; 3.2-fold] compared to those with moderate AHR (PC(20) < 1.0 mg/mL; 1.6-fold) [p = 0.04]. Three subjects with mild asthma and mild AHR (tidal-breathing PC(20), 1.9 to 4.3 mg/mL) had a nonmeasurable PC(20) (> 32 mg/mL) with the dosimeter.
The tidal-breathing method, which exposes the subject to twice as much aerosol at each concentration, produced approximately twice the response. The total lung capacity maneuvers with breathhold during the dosimeter method may inhibit the response in some patients with asthma.
美国胸科学会（ATS）最近发布了关于乙酰甲胆碱激发试验的2分钟潮气呼吸法和五次呼吸剂量计法的指南。尽管在任何给定浓度下，与剂量计法相比，潮气呼吸法中受试者接触的气雾剂量是其两倍，但人们认为两者结果相当。
比较2分钟潮气呼吸法和五次呼吸剂量计法的乙酰甲胆碱激发试验。
基于大学的三级医疗支气管激发实验室。
40名目前有症状的哮喘患者。
两种乙酰甲胆碱试验在不同日期、同一天的同一时间以随机顺序进行，间隔1至7天。
导致第一秒用力呼气容积（FEV₁）下降20%的乙酰甲胆碱剂量计激发浓度（PC₂₀）几乎是潮气呼吸法PC₂₀的两倍：2.4毫克/毫升对1.3毫克/毫升（配对t检验，p < 0.00005）。与中度气道高反应性（AHR）患者（PC₂₀ < 1.0毫克/毫升；1.6倍）相比，轻度AHR患者（PC₂₀ > 1.0毫克/毫升；3.2倍）的差异更大（p = 0.04）。三名轻度哮喘和轻度AHR患者（潮气呼吸法PC₂₀为1.9至4.3毫克/毫升）使用剂量计时PC₂₀无法测量（> 32毫克/毫升）。
在每个浓度下使受试者接触两倍气雾剂量的潮气呼吸法产生的反应约为两倍。剂量计法中屏气时的肺总量操作可能会抑制一些哮喘患者的反应。
