Ventilatory Inefficiency and Exertional Dyspnea in Early Chronic Obstructive Pulmonary Disease

• Published in: Annals of the American Thoracic Society Vol. 14; no. Supplement_1; pp. S22 - S29
• Main Authors: Neder, J Alberto, Berton, Danilo C, Müller, Paulo de Tarso, Elbehairy, Amany F, Rocha, Alcides, Palange, Paolo, O'Donnell, Denis E
• Format: Journal Article
• Language: English
• Published: United States 01-07-2017
• Subjects: Dyspnea - physiopathology; Exercise; Exercise Test; Exercise Tolerance; Humans; Oxygen Consumption; Pulmonary Disease, Chronic Obstructive - complications; Respiratory Insufficiency - physiopathology; Severity of Illness Index; Work of Breathing; exercise; cardiopulmonary exercise test; ventilation; chronic obstructive pulmonary disease
• ISSN: 2329-6933; 2325-6621
• DOI: 10.1513/AnnalsATS.201612-1033FR

Exertional dyspnea is present across the spectrum of chronic obstructive pulmonary disease (COPD) severity. However, without realizing it themselves, patients may decrease daily physical activity to avoid distressing respiratory sensations. Dyspnea also may be associated with deconditioning. Cardiopulmonary exercise testing can uncover exertional dyspnea and its physiological determinants in patients with preserved or only mildly reduced FEV
. Dyspnea in mild COPD can largely be explained by increased "wasted" ventilation in the physiological dead space, which heightens the drive to breathe and worsens the inspiratory mechanical constraints. During incremental exercise testing, this is readily identified as an excessive ventilation-to-metabolic demand, that is, a high ventilation ([Formula: see text]e) to carbon dioxide output ([Formula: see text]co
) relationship. Linking increases in [Formula: see text]e/[Formula: see text]co
to exertional dyspnea may provide objective evidence that a patient's poor exercise tolerance is not just a consequence of deconditioning. This information should prompt a proactive therapeutic approach to increase the available ventilatory reserve by, for example, giving inhaled bronchodilators. Considering that the structural determinants of ventilatory inefficiency (early emphysema, ventilation-perfusion mismatching, and microvascular disease) may progress despite only modest changes in FEV
, serial [Formula: see text]e/[Formula: see text]co
measurements might also prove valuable to track disease progression in these symptomatic patients.