title: Resting Physiological Correlates of Reduced Exercise Capacity in Smokers with Mild Airway Obstruction.
abstract: Smokers with minor spirometric abnormalities can experience persistent activity-related dyspnea and exercise intolerance. Additional resting tests can expose heterogeneous physiological abnormalities, but their relevance and association with clinical outcomes remain uncertain. Subjects included sixty-two smokers (≥20 pack-years), with cough and/or dyspnea and minor airway obstruction [forced expiratory volume in one-second (FEV1) ≥80% predicted and >5th percentile lower limit of normal (LLN) (i.e., z-score >-1.64) using the 2012-Global Lung Function Initiative equations]. They underwent spirometry, plethysmography, oscillometry, single-breath nitrogen washout, and symptom-limited incremental cycle exercise tests. Thirty-two age-matched nonsmoking controls were also studied. Thirty-three (53%) of smokers had chronic obstructive pulmonary disease by LLN criteria. In smokers [n = 62; age 65 ± 11 years; smoking history 43 ± 19 pack-years; post-bronchodilator FEV1z-score -0.60 ± 0.72 and FEV1/FVC z-score -1.56 ± 0.87 (mean ± SD)] versus controls, peak oxygen uptake (̇VO2) was 21 ± 7 vs. 32 ± 9 ml/kg/min, and dyspnea/̇VO2slopes were elevated (both p < 0.0001). Smokers had evidence of peripheral airway dysfunction and maldistribution of ventilation when compared to controls. In smokers versus controls: lung diffusing capacity for carbon monoxide (DLCO) was 85 ± 22 vs. 105 ± 17% predicted, and residual volume (RV)/total lung capacity (TLC) was 36 ± 8 vs. 31 ± 6% (both p < 0.01). The strongest correlates of peak ̇VO2were DLCO% predicted (r = 0.487, p < 0.0005) and RV/TLC% (r = -0.389, p = 0.002). DLCO% predicted was also the strongest correlate of dyspnea/̇VO2slope (r = -0.352, p = 0.005). In smokers with mild airway obstruction, associations between resting tests of mechanics and pulmonary gas exchange and exercise performance parameters were weak, albeit consistent. Among these, DLCO showed the strongest association with important outcomes such as dyspnea and exercise intolerance measured during standardized incremental exercise tests.
authors.affiliation: a Department of Medicine , Respiratory Investigation Unit, Queen's University and Kingston General Hospital , Kingston , ON , Canada.|b Department of Chest Diseases , Faculty of Medicine, Alexandria University , Alexandria , Egypt.
authors.forename: Amany F
authors.initials: AF
authors.lastname: Elbehairy
authors.affiliation: c Faculty of Physical Education for Men, Alexandria University , Alexandria , Egypt.|d School of Health Sport and Bioscience , University of East London , United Kingdom.
authors.forename: Azmy
authors.initials: A
authors.lastname: Faisal
authors.affiliation: e Department of Physical Therapy and UBC Centre for Heart Lung Innovation , University of British Columbia and St. Paul's Hospital , Vancouver , BC , Canada.
authors.forename: Jordan A
authors.initials: JA
authors.lastname: Guenette
authors.affiliation: f Department of Kinesiology & Physical Education , McGill University , Montreal , QC , Canada.
authors.forename: Dennis
authors.initials: D
authors.lastname: Jensen
authors.affiliation: a Department of Medicine , Respiratory Investigation Unit, Queen's University and Kingston General Hospital , Kingston , ON , Canada.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Webb
authors.affiliation: g College of Nursing and Professional Disciplines, University of North Dakota , Grand Forks , North Dakota , United States.
authors.forename: Rashid
authors.initials: R
authors.lastname: Ahmed
authors.affiliation: a Department of Medicine , Respiratory Investigation Unit, Queen's University and Kingston General Hospital , Kingston , ON , Canada.
authors.forename: J Alberto
authors.initials: JA
authors.lastname: Neder
authors.affiliation: a Department of Medicine , Respiratory Investigation Unit, 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; D000402:Airway Obstruction / Q000150:complications / Q000503:physiopathology*; D016022:Case-Control Studies; D003371:Cough / Q000209:etiology; D004417:Dyspnea / Q000209:etiology / Q000503:physiopathology; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology*; D012115:Residual Volume; D012146:Rest / Q000502:physiology*; D012907:Smoking / Q000009:adverse effects / Q000503:physiopathology*; D014797:Vital Capacity
keywords: Diffusing capacity; dyspnea; exercise; gas trapping; smokers