Enright P L, Lebowitz M D, Cockroft D W
Respiratory Sciences Center, University of Arizona College of Medicine, Tucson 85724.
Am J Respir Crit Care Med. 1994 Feb;149(2 Pt 2):S9-18; discussion S19-20. doi: 10.1164/ajrccm/149.2_Pt_2.S9.
When the effectiveness of asthma interventions are evaluated in the research setting, the physiologic manifestation of asthma-variable airways obstruction-is always objectively measured by some of the following pulmonary function tests: (1) Baseline spirometry gives a highly accurate "snapshot" of asthma severity and the degree of airways obstruction. The FEV1, derived from spirometry, is the most reproducible pulmonary function parameter and is linearly related to the severity of airways obstruction. There are no contraindications for the test, spirometers are widely available at reasonable cost, and methods and result interpretation are comprehensively standardized. (2) The post-bronchodilator FEV1 measures the best lung function that can be achieved by bronchodilator therapy on the day of the visit and therefore is a more stable measure in asthmatics than comparing visit-to-visit baseline FEV1. Although a positive acute response to bronchodilator helps to confirm the diagnosis of asthma, the degree of bronchodilator reversibility from visit-to-visit (change in reversibility) is not a useful index of asthma outcome. (3) Airway responsiveness (bronchial challenge) measures the degree to which an individual withstands nonspecific stimuli that trigger asthmatic attacks. The methacholine challenge test is safe and requires less than an hour, but it requires more technical skill than baseline spirometry and is contraindicated in some situations. (4) Ambulatory monitoring, using peak flow meters or hand-held spirometers, provides multiple measurements of the degree of obstruction for days to weeks in the patient's natural setting. PEF meters are very inexpensive and almost all asthmatics can use them, but PEF results are less reliable than the FEV1. The often asymptomatic obstruction of an asthmatic has both short-term (within a day and day-to-day) and longer-term variations that are triggered by naturally occurring stimuli. These changes are measured by PEF lability but not by spirometry during clinic visits. (5) Other pulmonary function tests, such as absolute lung volumes and airways resistance, may provide confirmatory data, but the instruments are large, expensive, and technically demanding. The results of all the above pulmonary function tests are significantly correlated with each other and with symptom scores and medication use in large groups of patients with widely varying degrees of asthma severity. Since a "gold standard" with which to measure asthma severity does not currently exist, all of these tests contribute an additional amount of unique information when measuring asthma outcome in a clinical trial.
在研究环境中评估哮喘干预措施的效果时，哮喘的生理表现——可变气道阻塞——总是通过以下一些肺功能测试进行客观测量：（1）基线肺量计检查能高度准确地“抓拍”哮喘严重程度和气道阻塞程度。从肺量计得出的第一秒用力呼气容积（FEV1）是最具可重复性的肺功能参数，且与气道阻塞严重程度呈线性相关。该测试没有禁忌证，肺量计价格合理且广泛可得，方法和结果解读也有全面的标准化。（2）支气管扩张剂后的FEV1测量的是就诊当天支气管扩张剂治疗所能达到的最佳肺功能，因此对于哮喘患者来说，它比比较就诊时的基线FEV1更稳定。虽然对支气管扩张剂的急性阳性反应有助于确诊哮喘，但就诊间支气管扩张剂可逆性的程度（可逆性变化）并非哮喘预后的有用指标。（3）气道反应性（支气管激发试验）测量个体对引发哮喘发作的非特异性刺激的耐受程度。乙酰甲胆碱激发试验安全且耗时不到一小时，但它比基线肺量计检查需要更多技术技巧，且在某些情况下有禁忌证。（4）使用峰值流量计或手持式肺量计进行动态监测，可在患者的自然环境中对阻塞程度进行数天至数周的多次测量。峰值呼气流量（PEF）计非常便宜，几乎所有哮喘患者都能使用，但PEF结果不如FEV1可靠。哮喘患者常出现的无症状性阻塞既有短期（一天内及每日）变化，也有由自然发生的刺激引发的长期变化。这些变化通过PEF变异性来测量，而不是通过就诊时的肺量计检查。（5）其他肺功能测试，如绝对肺容积和气道阻力，可能提供佐证数据，但仪器体积大、价格昂贵且技术要求高。上述所有肺功能测试的结果在哮喘严重程度差异很大的大量患者群体中彼此之间以及与症状评分和药物使用都显著相关。由于目前不存在用于衡量哮喘严重程度的“金标准”，在临床试验中测量哮喘预后时，所有这些测试都能提供额外的独特信息。
