Ward R J, Ward C, Johns D P, Skoric B, Abramson M, Walters E H
Dept of Psychiatry, University of Melbourne, Victoria, Australia.
Eur Respir J. 2002 Feb;19(2):252-6. doi: 10.1183/09031936.02.00224102.
Two potential sources of systematic variation in output from Mefar dosimeters, the system used in the European Community Respiratory Health Survey (ECRHS) study have been evaluated: individual nebulizer characteristics and dosimeter driving pressure. Output variation from 366 new nebulizers produced in two batches for the second ECRHS were evaluated, using a solute tracer method, at a fixed driving pressure. The relationship between dosimeter driving pressure was then characterized and between-centre variation in dosimeter driving pressure was evaluated in an Internet-based survey. A systematic difference between nebulizers manufactured in the two batches was identified. Batch one had a mean+/-SD output of 7.0+/-0.8 mg x s(-1) and batch two, 6.3+/-0.7 mg x s(-1) (p<0.005). There was a wide range of driving pressures generated by Mefar dosimeters as set, ranging between 70-245 kPa, with most outside the quoted manufacturer's specification of 180+/-5%. Nebulizer output was confirmed as linearly related to dosimeter driving pressure (coefficient of determination (R2)=0.99, output=0.0377 x driving pressure-0.4151). The range in driving pressures observed was estimated as consistent with a variation of about one doubling in the provocative dose causing a 20% fall in forced expiratory volume in one second. Systematic variation has been identified that constitutes potentially significant confounders for between-centre comparisons of airway responsiveness in the European Community Respiratory Health Survey, with the dosimeter driving pressure representing the most serious issue. This work confirms the need for appropriate quality control of both nebulizer output and dosimeter driving pressure, in laboratories undertaking field measurements of airway responsiveness. In particular, appropriate data on driving pressures need to be collected and factored into between-centre comparisons. Comprehensive collection of such data to optimize quality control is practicable and has been instigated by the organizing committee for the European Community Respiratory Health Survey II.
在欧洲共同体呼吸健康调查（ECRHS）研究中使用的Mefar剂量计输出的系统变化有两个潜在来源已被评估：个体雾化器特性和剂量计驱动压力。使用溶质示踪法，在固定驱动压力下评估了为第二次ECRHS分两批生产的366个新雾化器的输出变化。然后对剂量计驱动压力之间的关系进行了表征，并通过基于互联网的调查评估了剂量计驱动压力的中心间变化。确定了两批生产的雾化器之间存在系统差异。第一批的平均±标准差输出为7.0±0.8mg·s⁻¹，第二批为6.3±0.7mg·s⁻¹（p<0.005）。Mefar剂量计设定产生的驱动压力范围很广，在70 - 245kPa之间，大多数超出了制造商规定的180±5%的范围。雾化器输出被确认为与剂量计驱动压力呈线性相关（决定系数（R²）=0.99，输出=0.0377×驱动压力 - 0.4151）。观察到的驱动压力范围估计与激发剂量变化约一倍一致，这会导致一秒用力呼气量下降20%。已确定的系统变化可能是欧洲共同体呼吸健康调查中气道反应性中心间比较的潜在重要混杂因素，剂量计驱动压力是最严重的问题。这项工作证实了在进行气道反应性现场测量的实验室中，对雾化器输出和剂量计驱动压力进行适当质量控制的必要性。特别是，需要收集关于驱动压力的适当数据，并将其纳入中心间比较中。全面收集此类数据以优化质量控制是可行的，欧洲共同体呼吸健康调查II的组织委员会已推动此事。
