title: Mechanisms of exertional dyspnea in patients with cancer.
abstract: Exertional dyspnea is an important symptom in cancer patients, and, in many cases, its cause remains unexplained after careful clinical assessment. To determine mechanisms of exertional dyspnea in a variety of cancer types, we evaluated cancer outpatients with clinically important unexplained dyspnea (CD) at rest and during exercise and compared the results with age-, sex-, and cancer stage-matched control cancer (CC) patients and age- and sex-matched healthy control participants (HC). Participants (n = 20/group) were screened to exclude clinical cardiopulmonary disease and then completed dyspnea questionnaires, anthropometric measurements, muscle strength testing, pulmonary function testing, and incremental cardiopulmonary treadmill exercise testing. Dyspnea intensity was greater in the CD group at peak exercise and for a given ventilation and oxygen uptake (P < 0.05). Peak oxygen uptake was reduced in CD compared with HC (P < 0.05), and breathing pattern was more rapid and shallow in CD than in the other groups (P < 0.05). Reduced tidal volume expansion during exercise correlated with reduced inspiratory capacity, which, in turn, correlated with reduced inspiratory muscle strength. Patients with cancer had a relatively reduced diffusing capacity of the lung for carbon monoxide, reduced skeletal muscle strength, and lower ventilatory thresholds during exercise compared with HC (P < 0.05). There were no significant between-group differences in measurements of airway function, pulmonary gas exchange, or cardiovascular function during exercise. In the absence of evidence of airway obstruction or restrictive interstitial lung disease, the shallow breathing pattern suggests ventilatory muscle weakness as one possible explanation for increased dyspnea intensity at a given ventilation in CD patients.
authors.affiliation: Respiratory Investigation Unit, Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Travers
authors.forename: D J
authors.initials: DJ
authors.lastname: Dudgeon
authors.forename: K
authors.initials: K
authors.lastname: Amjadi
authors.forename: I
authors.initials: I
authors.lastname: McBride
authors.forename: K
authors.initials: K
authors.lastname: Dillon
authors.forename: P
authors.initials: P
authors.lastname: Laveneziana
authors.forename: D
authors.initials: D
authors.lastname: Ofir
authors.forename: K A
authors.initials: KA
authors.lastname: Webb
authors.forename: D E
authors.initials: DE
authors.lastname: O'Donnell
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D002908:Chronic Disease; D004417:Dyspnea / Q000209:etiology* / Q000503:physiopathology; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006801:Humans; D001239:Inhalation; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D009369:Neoplasms / Q000150:complications* / Q000503:physiopathology; D010101:Oxygen Consumption; D005082:Physical Exertion; D011659:Pulmonary Gas Exchange; D012123:Pulmonary Ventilation; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D012132:Respiratory Muscles / Q000503:physiopathology*; D011795:Surveys and Questionnaires; D013990:Tidal Volume