Small Airway Dysfunction in Chronic Bronchitis with Preserved Pulmonary Function
Qi Ding, Baibing Mi, Xia Wei, Jie Li, Jiuyun Mi, Jingting Ren, Ruili Li
Abstract
Impairment of pulmonary function was evaluated in chronic bronchitis patients with preserved ratio impaired spirometry (PRISm). We retrospectively collected clinical data from 157 chronic bronchitis (CB) and 186 chronic obstructive pulmonary disease (COPD) patients between October 2014 and September 2017. These patients were assigned to three groups: control (normal pulmonary function), PRISm (forced expiratory volume in 1 second [FEV1]/forced vital capacity [FVC] ≥ 0.7, FEV1 < 80% of predicted value), and COPD (FEV1/FVC <0.7) groups. Because small airway function was the main focus, in the COPD group, only patients in accordance with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) grades 1 and 2 were included. Evaluation of pulmonary function (including impulse oscillometry) was performed and compared among these groups. Compared with the control group, the PRISm and COPD groups showed statistically significant differences in the predicted FEV1% <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mfenced open="(" close=")" separators="|"> <a:mrow> <a:mi>p</a:mi> <a:mo><</a:mo> <a:mn>0.001</a:mn> </a:mrow> </a:mfenced> </a:math> , maximal expiratory flow (MEF) 25% <f:math xmlns:f="http://www.w3.org/1998/Math/MathML" id="M2"> <f:mfenced open="(" close=")" separators="|"> <f:mrow> <f:mi>p</f:mi> <f:mo><</f:mo> <f:mn>0.001</f:mn> </f:mrow> </f:mfenced> </f:math> , MEF50% <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" id="M3"> <k:mfenced open="(" close=")" separators="|"> <k:mrow> <k:mi>p</k:mi> <k:mo><</k:mo> <k:mn>0.001</k:mn> </k:mrow> </k:mfenced> </k:math> , maximal midexpiratory flow (MMEF) 25–75% <p:math xmlns:p="http://www.w3.org/1998/Math/MathML" id="M4"> <p:mfenced open="(" close=")" separators="|"> <p:mrow> <p:mi>p</p:mi> <p:mo><</p:mo> <p:mn>0.001</p:mn> </p:mrow> </p:mfenced> </p:math> , residual volume (RV)/total lung capacity (TLC; <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" id="M5"> <u:mi>p</u:mi> <u:mo><</u:mo> <u:mn>0.001</u:mn> </u:math> ), FVC% <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" id="M6"> <w:mfenced open="(" close=")" separators="|"> <w:mrow> <w:mi>p</w:mi> <w:mo><</w:mo> <w:mn>0.001</w:mn> </w:mrow> </w:mfenced> </w:math> , total respiratory resistance and proximal respiratory resistance (R5-R20; <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML" id="M7"> <bb:mi>p</bb:mi> <bb:mo><</bb:mo> <bb:mn>0.001</bb:mn> </bb:math> ), respiratory system reactance at 5 Hz (X5; <db:math xmlns:db="http://www.w3.org/1998/Math/MathML" id="M8"> <db:mi>p</db:mi> <db:mo><</db:mo> <db:mn>0.001</db:mn> </db:math> ), resonant frequency (Fres; <fb:math xmlns:fb="http://www.w3.org/1998/Math/MathML" id="M9"> <fb:mi>p</fb:mi> <fb:mo><</fb:mo> <fb:mn>0.001</fb:mn> </fb:math> ), and area of reactance (Ax; <hb:math xmlns:hb="http://www.w3.org/1998/Math/MathML" id="M10"> <hb:mi>p</hb:mi> <hb:mo><</hb:mo> <hb:mn>0.001</hb:mn> </hb:math> ). However, the predicted FEV1% and RV/TLC were similar between the PRISm and COPD groups ( <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML" id="M11"> <jb:mi>p</jb:mi> <jb:mo>=</jb:mo> <jb:mn>0.992</jb:mn> </jb:math> and 0.122, respectively). PRISm is a nonspecific pattern of pulmonary function that indicates small airway dysfunction and may increase the risk of transformation to obstructive ventilation dysfunction. This trial is registered with ChiCTR-OCH-14004904.