Assessment of dyspnea and dynamic hyperinflation in male patients with chronic obstructive pulmonary disease during a six minute walk test and an incremental treadmill cardiorespiratory exercise test

The six minute walk test (6MWT) is a standardized test that provides information on exercise capacity in patients with COPD. It is considered a submaximal test in opposition to incremental cardiopulmonary exercise tests (CPET) that provide valuable information on all the systems involved in exercise.

Objectives

1. To compare the perceptive, physiological responses and degree of dynamic hyperinflation during two exercise tests: the 6MWT and the incremental CPET on a treadmill. 2. To evaluate how dyspnea is related to dynamic hyperinflation (DH) and other functional parameters in both tests.

Methods

29 stable COPD male patients, age 68 ± 5.8 years, mean post-bronchodilator FEV1 57 ± 11%, were recruited. To evaluate dynamic hyperinflation, inspiratory capacity (IC) was measured at rest and upon completing each one of the tests. At the same time, perceived dyspnea and leg discomfort were rated on specific modified Borg scales.

Results

The mean walk distance in 6MWT was 494 ± 88 m. The Borg scale rating for shortness of breath upon completing the test was 4.7 ± 2, whilst 2.9 ± 2 for leg discomfort. IC changed from 2.53 ± 0.63 l before to 2.34 ± 0.60 l after completion of the test.

In the treadmill CPET, maximal oxygen consumption ($\dot{\text{V}}{\text{O}}_2\max$) was 21.8 ± 5 mL/kg/min with 6.6 ± 2 dyspnea and 4.3 ± 2 leg discomfort on Borg scales. IC changed from 2.17 ± 0.53 l to 1.20 ± 0.43 l.

Conclusions

Dynamic hyperinflation occurs in male COPD patients during submaximal exercise such as the 6MWT. This phenomenon is more pronounced after incremental CPET on a treadmill. Despite being dyspnea the dominant limiting symptom for both tests, we observed different physiological responses.