The outcome measurements for dyspnea can be
broadly divided into those that assess breathlessness
during exercise (laboratory dyspnea), and those that assess overall breathlessness during daily activities (clinical
dyspnea). Using factor analysis, Hajiro et al. [10]
reported that various clinical dyspnea ratings were virtually
identical for evaluating dyspnea in COPD patients.
On the other hand, dyspnea at the end of maximal exercise
may provide a different type of information regarding
dyspnea [10]. It has also been reported that dyspnea
during daily activities was more significantly correlated
with objective and subjective measurements of COPD
than dyspnea at the end of exercise, and that the former
was more predictive of mortality [11]. Therefore, dyspnea
while performing the activities of daily living is
considered to be a better measurement for evaluating
the disease severity of COPD than peak dyspnea during
exercise.