Physiological impairment in mild COPD

Abstract

Chronic obstructive pulmonary disease (COPD) is a common and often progressive inflammatory disease of the airways, alveoli and microvasculature that is both preventable and treatable. It is well established that smokers with mild airway obstruction, as spirometrically defined, represent the vast majority of patients with COPD, yet this population has not been extensively studied. An insidious preclinical course means that mild COPD is both underdiagnosed and undertreated. In this context, recent studies have confirmed that even patients with mild COPD can have extensive physiological impairment, which contributes to poor perceived health status compared with non-smoking healthy controls. This review describes the heterogeneous pathophysiology that can exist in COPD patients with only mild airway obstruction on spirometry. It exposes the compensatory adaptations that develop in such patients to ensure that the respiratory system fulfils its primary task of maintaining adequate pulmonary gas exchange for the prevailing metabolic demand. It demonstrates that adaptations such as increased inspiratory neural drive to the diaphragm due to combined effects of increased mechanical loading and chemostimulation underscore the increased dyspnoea and exercise intolerance in this population. Finally, based on available evidence, we present what we believe is a sound physiological rationale for earlier diagnosis in this population.

Year in review 2016: Chronic obstructive pulmonary disease and asthma

“…The major structural abnormalities in patients with COPD include increased thickness of the ASM layer, airway wall remodelling and destruction of peripheral airways . In smokers with normal spirometry and patients with mild COPD, functional changes of the airways have been noted . In smokers with normal spirometry, conductive airway dysfunction is partly due to increased bronchomotor tone while acinar airway dysfunction is not .…”

“…In smokers with normal spirometry, conductive airway dysfunction is partly due to increased bronchomotor tone while acinar airway dysfunction is not . O'Donnell et al ., in a review article, described the heterogeneous pathophysiology that can exist in COPD patients with only mild airway obstruction on spirometry . Lung function assessments measure the functional abnormalities of COPD patients.…”

COPD: Lessons learned, forging a fantastic future

“…The two primary processes that lead to COPD are: (i) accelerated decline in lung function in adulthood and (ii) poor lung growth during childhood . While most patients with COPD have mild disease (forced expiratory volume in 1 s (FEV 1 ) >80% of predicted with FEV 1 /forced vital capacity (FVC) ratio <70%), many of these patients are symptomatic (when challenged) and indeed, they have the greatest rate of FEV 1 decline . For example, an incremental exercise test reveals that these patients are frequently ventilation‐limited in their exercise tolerance and bronchodilators improve their exercise performance .…”

“…While most patients with COPD have mild disease (forced expiratory volume in 1 s (FEV 1 ) >80% of predicted with FEV 1 /forced vital capacity (FVC) ratio <70%), many of these patients are symptomatic (when challenged) and indeed, they have the greatest rate of FEV 1 decline . For example, an incremental exercise test reveals that these patients are frequently ventilation‐limited in their exercise tolerance and bronchodilators improve their exercise performance . It is thus important to encourage physical activity in COPD patients, even in the earliest stages of disease .…”

“…4 For example, an incremental exercise test reveals that these patients are frequently ventilation-limited in their exercise tolerance and bronchodilators improve their exercise performance. 5 It is thus important to encourage physical activity in COPD patients, even in the earliest stages of disease. 6 It is important that when exercise targets are set, clinicians should set achievable goals by outlining initially a low-intensity programme that patients can perform as part of their 'daily routine'.…”