Chiari Stefania, Bassini Sonia, Braghini Alessia, Corda Luciano, Boni Enrico, Tantucci Claudio
1Unit of Respiratory Medicine, Department of Medical and Surgical Sciences, University of Brescia , Brescia , Italy.
COPD. 2014 Feb;11(1):33-8. doi: 10.3109/15412555.2013.813929. Epub 2013 Oct 8.
Tidal expiratory flow limitation (EFL) is a step of paramount importance in the functional decline in COPD. Among mechanisms contributing to EFL, loss of airway-parenchymal interdependence could mostly be involved.
To assess if EFL is a functional marker more frequently linked to prevalent pulmonary emphysema rather than to prevalent chronic bronchiolitis in COPD patients with moderate-to-severe airflow obstruction.
Forty consecutive stable COPD patients with FEV1 between 59 and 30% of predicted were functionally evaluated by measuring spirometry, maximal flow-volume curve and lung diffusion capacity (DLCO) and coefficient of diffusion (KCO). EFL was assessed by the negative expiratory pressure (NEP) method both in sitting and supine position. Chronic dyspnea was also scored by modified Medical Research Council (mMRC) scale.
In sitting position 13 patients (33%) were flow limited (FL) and 27 were non-flow limited (NFL). Only FEV1/FVC, FEV1 and MEF25-75% were different between FL and NFL patients (p < 0.01). In supine position, however, among NFL patients in sitting position those who developed EFL, had significantly lower values of DLCO and KCO (p < 0.05) and higher mMRC score (p < 0.01), but similar values of FEV1 as compared to those who did not have EFL.
In COPD EFL in sitting position is highly dependent by the severity of airflow obstruction. In contrast, the occurrence of EFL in supine position is associated with worse DLCO and KCO and greater chronic dyspnea, reflecting a prevalent emphysematous phenotype in moderate-to-severe COPD patients.
呼气气流受限（EFL）是慢性阻塞性肺疾病（COPD）功能下降过程中极为重要的一个环节。在导致EFL的机制中，气道与实质组织间相互依存关系的丧失可能起主要作用。
评估在中重度气流受限的COPD患者中，EFL是否作为一种功能标志物，与普遍存在的肺气肿的关联比与普遍存在的慢性细支气管炎更为密切。
对40例连续的稳定期COPD患者进行功能评估，这些患者的第1秒用力呼气容积（FEV1）为预计值的59%至30%，通过测量肺量计、最大流量-容积曲线、肺弥散功能（DLCO）和弥散系数（KCO）来进行评估。采用呼气负压（NEP）法在坐位和仰卧位评估EFL。慢性呼吸困难也采用改良的医学研究委员会（mMRC）量表进行评分。
在坐位时，13例患者（33%）存在气流受限（FL），27例患者无气流受限（NFL）。FL组和NFL组患者之间仅FEV1/FVC、FEV1和MEF25-75%存在差异（p<0.01）。然而，在仰卧位时，坐位时无气流受限的患者中出现EFL的患者，其DLCO和KCO值显著更低（p<0.05），mMRC评分更高（p<0.01），但与未出现EFL的患者相比，FEV1值相似。
在COPD中，坐位时的EFL高度依赖于气流阻塞的严重程度。相比之下，仰卧位时EFL的出现与更差的DLCO和KCO以及更严重的慢性呼吸困难相关，反映了中重度COPD患者普遍存在的肺气肿表型。
