Chest
Volume 136, Issue 6, December 2009, Pages 1466-1472
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Original Research
COPD
Measurement of Dynamic Hyperinflation After a 6-Minute Walk Test in Patients With COPD

https://doi.org/10.1378/chest.09-0410Get rights and content

Background

Dynamic hyperinflation (DH) develops in patients with COPD during incremental exercise with a cycle ergometer. The aims of this study were to determine whether DH can be evidenced after walking with a handheld spirometer and to determine its functional consequences.

Methods

Fifty patients with COPD (39 men; median age, 60 years [interquartile range (IQR), 54 to 69 years]; FEV1, 45% predicted [IQR, 31 to 67% predicted]) underwent pulmonary function tests and a 6-min walk test (6MWT). Inspiratory capacity (IC) was measured with the patient in the standing position at rest and immediately after the 6MWT with a portable spirometer. Dyspnea was evaluated directly (change in Borg score during 6MWT) and indirectly (Medical Research Council scale). The first 20 patients performed an incremental exercise test with cycle ergometer that allowed for the measurement of IC at peak exercise and repeatedly during the first 3 min of recovery.

Results

The median change in IC during the 6MWT was −210 mL (IQR, 55 to −440; n = 50), whereas the median change in IC during the exercise test was −295 mL (IQR, −145 to −515; n = 20). Both the IC and IC changes after 6MWT correlated to values after the exercise test. DH decreased rapidly after the end of the exercise test but was nonsignificantly different from the baseline value after 75 s of recovery. The percentage of decrease in IC during the 6MWT correlated with dyspnea (change in Borg score during 6MWT: r2 = 0.21; p = 0.0006).

Conclusions

DH can be measured during a 6MWT with a handheld spirometer to allow for its evaluation in daily practice and its contribution to dyspnea while walking.

Section snippets

Design

The first 20 patients underwent both a 6MWT and an exercise test with cycle ergometer to allow for the comparison of ICs obtained from both tests (part of their checkup before rehabilitation). Thirty additional patients, who had performed a 6MWT and had undergone additional indirect measures of dyspnea (ie, measurement of the baseline dyspnea index [BDI] and the number of flights of stairs walked), were included in the study (Fig 1).

Patients

Patients with COPD were enrolled consecutively and were

Results

The clinical and functional characteristics of the 50 patients with COPD are described in Table 1. Their median age was 60 years (range, 54 to 69 years), and the median FEV1 was 45% predicted (range, 31% to 67% predicted).

The IC measured with the patient in the standing position (before the 6MWT) tended to be higher than that with the patient in the sitting position for all patients (p = 0.064). The median change in IC during the 6MWT for all patients was −210 mL (range, 55 to −440 mL), whereas

Discussion

The main results of this study are the demonstration that DH can be easily assessed after a 6MWT, correlated to that measured during an incremental exercise test, and correlated to both direct and indirect measures of dyspnea, whereas performance during the 6MWT was mainly related to hyperinflation at rest. Our methodological measurement of IC was different from that adopted by Marin et al.2 In their study, IC was determined using pneumotachography by having the patients inhale while seated.

Acknowledgments

Author contributions: Drs. Callens, Graba, Gillet-Juvin, and Essalhi carried out the measurements of IC at walk, participated in the design of the study, and drafted the manuscript. Dr. Bidaud-Chevalier participated in data collection and helped to draft the manuscript. Drs. Peiffer and Mahut participated in the design, performed the statistical analysis, and helped to draft the manuscript. Dr. Delclaux conceived of the study, performed exercise tests, participated in its design and

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