Fig. 2.

Dyspnea break-point (point A). First, a dyspnea break-point was determined for each patient by using the intersection of two lines on plots of dyspnea as a function of ${\dot{V}}_{{\mathrm{O}}_2}$. Second, the location (%) of each resulting dyspnea break-point relative to Δ${\dot{V}}_{{\mathrm{O}}_2}$ (= peak ${\dot{V}}_{{\mathrm{O}}_2}$ − resting ${\dot{V}}_{{\mathrm{O}}_2}$) that occurs during exercise was calculated for each patient by use of the equation 100 × (dyspnea break-point ${\dot{V}}_{{\mathrm{O}}_2}$ − resting ${\dot{V}}_{{\mathrm{O}}_2}$)/Δ${\dot{V}}_{{\mathrm{O}}_2}$. 50 % ${\dot{V}}_{{\mathrm{O}}_2}$ point (point B). The ${\dot{V}}_{{\mathrm{O}}_2}$ value at the 50 % ${\dot{V}}_{{\mathrm{O}}_2}$ point was calculated for each patient by use of the equation resting ${\dot{V}}_{{\mathrm{O}}_2}$ + (peak ${\dot{V}}_{{\mathrm{O}}_2}$ − resting ${\dot{V}}_{{\mathrm{O}}_2}$)/2. Next, the value of the Borg scale at the 50 % ${\dot{V}}_{{\mathrm{O}}_2}$ point was calculated for each patient, where the Borg scale on the Y axis corresponded to the 50 % ${\dot{V}}_{{\mathrm{O}}_2}$ point on the X axis by linear interpolation between adjacent measurement points