title: Exercise ventilatory inefficiency in mild to end-stage COPD.
abstract: Ventilatory inefficiency during exercise is a key pathophysiological feature of chronic obstructive pulmonary disease. Currently, it is unknown how this physiological marker relates to clinically relevant outcomes as resting ventilatory impairment progresses across disease stages. Slope and intercept of the linear region of the ventilation-carbon dioxide output relationship and the ratio between these variables, at the lowest point (nadir), were contrasted in 316 patients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages 1-4 (forced expiratory volume in 1 s, ranging from 148% pred to 12% pred) and 69 aged- and gender-matched controls, Compared to controls, slope and intercept were higher in GOLD stages 1 and 2, leading to higher nadirs (p<0.05). Despite even larger intercepts in GOLD stages 3 and 4, slopes diminished as disease evolved (from mean±sd 35±6 in GOLD stage 1 to 24±5 in GOLD stage 3, p<0.05). As a result, there were no significant differences in nadirs among patient groups. Higher intercepts, across all stages (p<0.01), and to a lesser extent lower slopes in GOLD stages 2-4 (p<0.05), were related to greater mechanical constraints, worsening pulmonary gas exchange, higher dyspnoea scores, and poorer exercise capacity. Increases in the ventilation intercept best indicate the progression of exercise ventilatory inefficiency across the whole spectrum of chronic obstructive pulmonary disease severity.
authors.affiliation: Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, ON, Canada Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
authors.affiliation: Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Flavio F
authors.initials: FF
authors.lastname: Arbex
authors.affiliation: Clinical Exercise Physiology Unit (SEFICE), Division of Respirology, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: Maria Clara N
authors.initials: MC
authors.lastname: Alencar
authors.affiliation: Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Conor D J
authors.initials: CD
authors.lastname: O'Donnell
authors.affiliation: Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Julia
authors.initials: J
authors.lastname: Cory
authors.affiliation: Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Kathy A
authors.initials: KA
authors.lastname: Webb
authors.affiliation: Respiratory Investigation Unit and Laboratory of Clinical Exercise Physiology, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors.forename: Denis E
authors.initials: DE
authors.lastname: O'Donnell
mesh_terms: D000368:Aged; D002245:Carbon Dioxide; D016022:Case-Control Studies; D018450:Disease Progression; D004417:Dyspnea / Q000503:physiopathology; D015444:Exercise; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis* / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange; D012119:Respiration; D012129:Respiratory Function Tests; D012146:Rest; D012189:Retrospective Studies; D012720:Severity of Illness Index; D016896:Treatment Outcome
chemical_list: D002245:Carbon Dioxide