title: Dyspnea, ventilatory pattern, and changes in dynamic hyperinflation related to the intensity of constant work rate exercise in COPD.
abstract: OBJECTIVE
  We undertook the present study to investigate the perception of dyspnea (with respect to changes in end-inspiratory and end-expiratory lung volumes), during four different levels of high-intensity constant work rate exercise (CWRE) in patients with severe COPD.
  
  
  METHODS
  Crossover descriptive study with consecutively recruited subjects.
  
  
  METHODS
  Tertiary university hospital.
  
  
  METHODS
  Twenty-seven subjects with severe COPD (mean [+/- SD] age, 65 +/- 5 years of age; mean FEV1, 43 +/- 8% predicted; and mean inspiratory capacity [IC]; 74 +/- 14% predicted).
  
  
  RESULTS
  Subjects randomly performed four high-intensity CWRE tests (conducted at 65%, 75%, 85%, and 95% of their symptom-limited peak work rate). Dyspnea, leg fatigue, and IC were determined every 2 min during exercise with breath-by-breath gas exchange and ventilatory measurements. There was a good correlation between the resting IC percent predicted and the oxygen uptake (V(O2)) peak (r = 0.64 to 0.69 between the IC percent predicted and V(O2) peak at the four work rates). There were significant differences (p < 0.01) in mean respiratory rate (33 +/- 6, 35 +/- 6, 37 +/- 6, and 38 +/- 6 min), peak dyspnea score (5.9 +/- 1.3, 6.3 +/- 1.4, 6.8 +/- 1.2, and 6.9 +/- 1.6), minute ventilation (45.0 +/- 8.7, 43.8 +/- 7.7, 43.1 +/- 8.7, and 42.8 +/- 8.0 L/min), leg fatigue (4.8 +/- 1.3, 5.1 +/- 1.3, 5.7 +/- 1.4, and 5.8 +/- 1.4), and end-tidal carbon dioxide partial pressure (4.41 +/- 0.36, 4.53 +/- 0.33, 4.66 +/- 0.31, and 4.76 +/- 0.24 kPa), respectively, for tests conducted at 65%, 75%, 85%, and 95% of their symptom-limited peak work rate, and in mean end-expiratory lung volume ([EELV] 4.55 +/- 0.44, 4.69 +/- 0.43, and 4.79 +/- 0.43 L), respectively, for tests conducted at 65%, 75%, and 85% of their symptom-limited peak work rate. In multivariable analysis, the factors that were independently correlated with dyspnea (p < 0.05) were EELV, peak inspiratory flow, and leg fatigue/discomfort.
  
  
  CONCLUSIONS
  In COPD subjects with flow limitation at rest, the perception of dyspnea increased nonlinearly with the magnitude of high-intensity CWRE in association with a faster respiratory pattern and an increase in EELV. At the highest work rates, it appeared that a reduction in tidal volume and ventilation peak may have limited the tolerance to exercise.
authors.affiliation: Hospital General Universitario Gregorio Marañón, Servicio de Neumología, c/o Doctor Ezquerdo 46, 28007 Madrid, Spain. lpuente@separ.es
authors.forename: Luis
authors.initials: L
authors.lastname: Puente-Maestu
authors.forename: Julia
authors.initials: J
authors.lastname: García de Pedro
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Martínez-Abad
authors.forename: José Maria
authors.initials: JM
authors.lastname: Ruíz de Oña
authors.forename: Daniel
authors.initials: D
authors.lastname: Llorente
authors.forename: José Manuel
authors.initials: JM
authors.lastname: Cubillo
mesh_terms: D000368:Aged; D018592:Cross-Over Studies; D004417:Dyspnea / Q000503:physiopathology*; D015444:Exercise; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D012720:Severity of Illness Index