Dyspnea, ventilatory pattern, and changes in dynamic hyperinflation related to the intensity of constant work rate exercise in COPD.
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.
Puente-Maestu
Luis
L
Hospital General Universitario Gregorio Marañón, Servicio de Neumología, c/o Doctor Ezquerdo 46, 28007 Madrid, Spain. lpuente@separ.es
García de Pedro
Julia
J
Martínez-Abad
Yolanda
Y
Ruíz de Oña
José Maria
JM
Llorente
Daniel
D
Cubillo
José Manuel
JM
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