title: Ventilatory Inefficiency and Exertional Dyspnea in Early Chronic Obstructive Pulmonary Disease.
abstract: 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 FEV1. 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]co2) relationship. Linking increases in [Formula: see text]e/[Formula: see text]co2to 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 FEV1, serial [Formula: see text]e/[Formula: see text]co2measurements might also prove valuable to track disease progression in these symptomatic patients.
authors.affiliation: 1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
authors.affiliation: 1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.|2 Division of Respiratory Medicine, Federal University of Rio Grande do Sul, Porto Alegre, Brazil.
authors.forename: Danilo C
authors.initials: DC
authors.lastname: Berton
authors.affiliation: 3 Laboratory of Respiratory Pathophysiology, Respiratory Division, Department of Medicine, Federal University of Mato Grosso do Sul, Campo Grande, Mato Grosso do Sul, Brazil.
authors.forename: Paulo de Tarso
authors.initials: PT
authors.lastname: Müller
authors.affiliation: 1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.|4 Department of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors.forename: Amany F
authors.initials: AF
authors.lastname: Elbehairy
authors.affiliation: 5 Respiratory Division, Pulmonary Function and Clinical Exercise Physiology, Federal University of Sao Paulo, Sao Paulo, Brazil; and.
authors.forename: Alcides
authors.initials: A
authors.lastname: Rocha
authors.affiliation: 6 Department of Public Health and Infectious Diseases, Sapienza University of Rome, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Palange
authors.affiliation: 1 Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, Ontario, Canada.
authors.forename: Denis E
authors.initials: DE
authors.lastname: O'Donnell
mesh_terms: D004417:Dyspnea / Q000503:physiopathology*; D015444:Exercise; D005080:Exercise Test; D017079:Exercise Tolerance; D006801:Humans; D010101:Oxygen Consumption; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications*; D012131:Respiratory Insufficiency / Q000503:physiopathology*; D012720:Severity of Illness Index; D014939:Work of Breathing
keywords: cardiopulmonary exercise test; chronic obstructive pulmonary disease; exercise; ventilation