Chest

Chest

Volume 128, Issue 2, August 2005, Pages 651-656
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Clinical Investigations
Dyspnea, Ventilatory Pattern, and Changes in Dynamic Hyperinflation Related to the Intensity of Constant Work Rate Exercise in COPD

https://doi.org/10.1378/chest.128.2.651Get rights and content

Study 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

Design

Crossover descriptive study with consecutively recruited subjects

Setting

Tertiary university hospital

Patients

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)

Measurements and 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.o2peak 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

Conclusion

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

Section snippets

Study Design, Study Group, and Settings

The present investigation was designed as a crossover study in which each patient randomly performed four high-intensity CWRE tests. The subjects of the study were recruited from a population of patients with severe COPD according to American Thoracic Society guidelines 11 with no significant acute reversibility (ie, < 12% increase in FEV115 min after the administration of 400 μg of salbutamol) who stopped smoking at least 6 months before enrolling in the study. From this population, those who

Results

Twenty-seven patients participated in this study, and their physical characteristics are presented in Table 1. As a group, they had a mean body weight slightly below normal, with moderate hypoxemia and no CO2retention at rest. The patients had moderate hyperinflation and moderately reduced diffusing capacity of the lung for carbon monoxide. They also had moderately impaired aerobic capacity. Nineteen of the 27 patients (70%) had an IC that was < 80% predicted.

Dyspnea followed a different time

Discussion

There were several relevant findings in this study of CWRE in patients with severe COPD. First, patients stopped the test at peak V.elevels that decreased in a progressive, statistically significant fashion. In contrast, the perception of dyspnea at the end of exercise progressively increased with the intensity of the CWRE. The relationship between dyspnea and V.ewas, therefore, different for each CWRE intensity. Furthermore, if we consider the set of four work-rate peak dyspnea

Acknowledgments

We thank Dr. William W. Stringer for his help with the manuscript. This study was funded by Fondo de Investigaciones Sanitarias Grant 96/2042 and by the Spanish Pulmonary and Thoracic Surgery Society.

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    This study was supported by a grant from the Fondo deInvestigaciones Sanitarias (grant No. 96/2042) and SociedadEspanola de Neumología y Ciruga Toracica.

    Reproduction of this article is prohibited without written permissionfrom the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml)

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    Copyright © 2005 The American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.