Click on image to view larger version.
Figure 1 Data from a patient with PPH with illustration of the components of the single-exponential curves used to describe the exercise and recovery responses. In each case, the exponential function starts after a time delay. Exercise: 
O2 = c + A(1 – e-(t – td)/
), where c is preexercise baseline O2; A is amplitude from baseline to asymptotic value; td is time delay; and is time constant. Recovery: O2 = c + Ae-(t – td)/, where c is end-recovery asymptotic O2; A is amplitude of response; td is time delay; and is time constant.