However, the x-intercept for the VE-dyspnea relationship was significantly higher in patients with COPD compared with healthy subjects. These findings are consistent with previous observations that VE is higher at similar exercise intensities in patients with COPD compared to normal subjects, due, at least in part, to an increase in dead space ventilation.
The absolute threshold may be an important parameter to consider in evaluating breathlessness during exercise testing. For example, Killian and colleagues2 estimated that the thresholds for leg effort and dyspnea occurred “between 20% and 40% of maximal power output” based on discrete perceptual ratings. Although Teramoto et al termed the V02 on the x-intercept as the “threshold load of dyspnea,” it is not possible to calculate an absolute threshold based on the discrete method for rating breathlessness. storehealthmall.eu
Rather, the continuous method enables the direct measurement of a threshold that we identify as “just noticeable” breathlessness on the Borg scale. The absolute threshold may prove to be a useful new metric because many patients describe slowing down or even stopping an activity when they first experience the onset of breathlessness. One possible explanation for this strategy is that patients typically try to minimize intense distress associated with breathing, and therefore avoid further physical activity. In an earlier report, we found that healthy elderly subjects had lower physiologic values for the absolute threshold during cycle ergometry compared with healthy, college-aged subjects. It remains to be determined whether the corresponding physiologic values for the absolute threshold of breathlessness are useful in evaluating the efficacy of various interventions or treatments.