title: Mechanisms of exertional dyspnoea in symptomatic smokers without COPD.
abstract: Dyspnoea and activity limitation can occur in smokers who do not meet spirometric criteria for chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are unknown.Detailed pulmonary function tests and sensory-mechanical relationships during incremental exercise with respiratory pressure measurements and diaphragmatic electromyography (EMGdi) were compared in 20 smokers without spirometric COPD and 20 age-matched healthy controls.Smokers (mean±sd post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity 75±4%, mean±sd FEV1 104±14% predicted) had greater activity-related dyspnoea, poorer health status and lower physical activity than controls. Smokers had peripheral airway dysfunction: higher phase-III nitrogen slopes (3.8±1.8 versus 2.6±1.1%·L(-1)) and airway resistance (difference between airway resistance measured at 5 Hz and 20 Hz 19±11 versus 12±7% at 5 Hz) than controls (p<0.05). Smokers had significantly (p<0.05) lower peak oxygen uptake (78±40 versus 107±45% predicted) and ventilation (61±26 versus 97±29 L·min(-1)). Exercise ventilatory requirements, operating lung volumes and cardio-circulatory responses were similar. However, submaximal dyspnoea ratings, resistive and total work of breathing were increased in smokers compared with controls (p<0.05); diaphragmatic effort (transdiaphragmatic pressure/maximumal transdiaphragmatic pressure) and fractional inspiratory neural drive to the diaphragm (EMGdi/maximal EMGdi) were also increased (p<0.05) mainly reflecting the reduced denominator.Symptomatic smokers at risk for COPD had greater exertional dyspnoea and lower exercise tolerance compared with healthy controls in association with greater airways resistance, contractile diaphragmatic effort and fractional inspiratory neural drive to the diaphragm.
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada Dept of Chest Diseases, Faculty of Medicine, Alexandria University, Alexandria, Egypt.
authors: Amany F
authors: AF
authors: Elbehairy
authors: Dept of Physical Therapy and UBC Centre for Heart Lung Innovation, University of British Columbia and St. Paul's Hospital, Vancouver, BC, Canada.
authors: Jordan A
authors: JA
authors: Guenette
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada Faculty of Physical Education for Men, Alexandria University, Alexandria, Egypt.
authors: Azmy
authors: A
authors: Faisal
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors: Casey E
authors: CE
authors: Ciavaglia
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors: Katherine A
authors: KA
authors: Webb
authors: Dept of Kinesiology & Physical Education, McGill University, Montreal, QC, Canada.
authors: Dennis
authors: D
authors: Jensen
authors: Dept of Physical Therapy and UBC Centre for Heart Lung Innovation, University of British Columbia and St. Paul's Hospital, Vancouver, BC, Canada.
authors: Andrew H
authors: AH
authors: Ramsook
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada.
authors: J Alberto
authors: JA
authors: Neder
authors: Respiratory Investigation Unit, Department of Medicine, Queen's University and Kingston General Hospital, Kingston, ON, Canada odonnell@queensu.ca.
authors: Denis E
authors: DE
authors: O'Donnell
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D003964:Diaphragm / Q000503:physiopathology; D004417:Dyspnea / Q000503:physiopathology*; D004576:Electromyography; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010100:Oxygen / Q000737:chemistry; D010641:Phenotype; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012119:Respiration; D012129:Respiratory Function Tests; D012306:Risk; D012907:Smoking; D013147:Spirometry; D014797:Vital Capacity
chemical_list: D010100:Oxygen