Relationships between airway resistances and activity-related dyspnea in patients with stable chronic obstructive pulmonary disease

Abstract

Objective To observe the relationship between the airway resistance (Raw) and activity-related dyspnea in patients with chronic obstructive pulmonary disease (COPD). Methods This was a prospective study with 180 patients with COPD (Global Initiative for Chronic Obstructive Lung Disease 2017 stages Ⅰ-Ⅳ) who presented at the outpatient clinic of the Shanghai Chest Hospital and Shanghai general hospital, from December 2017 to March 2019.Spirometry testing and respiratory resistance components were measured by plethysmography after brochodilator (salbutamol 400 μg) inhalation. Results Compared with 42 healthy elder and 30 mild COPD patients, The first second forced expiratory volume and forced expiratory flow at 50% vital capacity in patients with GOLD stages Ⅱ-Ⅳ were significantly lower.The total airway resistance (Rtot), effective airway resistance (Reff), inspiratory airway resistance (Rinsp) and expiratory airway resistance (Rexp) of the moderate and severe COPD patients were significantly higher than those of the healthy elder group.The inspiratory capacity (IC) of patients with GOLD stages Ⅲ-Ⅳ is under 80% of the predicted value, which mMRC score was exceed 2.One patient (1.9%) with GOLD stageⅡ, 7(13.2%) patients with GOLD stage Ⅲ and 14(33.3%) patients with GOLD stage Ⅳ revealed inspiratory fraction (IC/TLC ratio) ≤25%. Conclusions Raw, especially expiratory airway resistance were obviously increased in stable moderate to severe COPD patients on account of the severe expiratory flow limitation. According to the aggravation of peripheral airway inflammation, activity-related dyspnea symptoms were more prone to occured in COPD patients with GOLD stages Ⅲ-Ⅳ, and IC/TLC ratio might more likely to be below 25%. Key words: Pulmonary disease, chronic obstructive; Airway resistance; Inspiratory fraction