Volume 105, Issue 6, Pages 1693-1700 (June 1994) Dynamics of Oxygen Uptake for Submaximal Exercise and Recovery in Patients With Chronic Heart Failure  Kathy E. Sietsema, M.D., Issahar Ben-Dov, M.D., Yong Yu Zhang, M.D., Cynthia Sullivan, M.S., Karlman Wasserman, M.D., Ph.D., F.C.C.P.  CHEST  Volume 105, Issue 6, Pages 1693-1700 (June 1994) DOI: 10.1378/chest.105.6.1693 Copyright © 1994 The American College of Chest Physicians Terms and Conditions

FIGURE 1 Characterization of oxygen uptake ( V ˙ o 2 ) kinetics for constant work rate exercise. Exercise begins at time 0. Panel A shows determination of end-exercise V ˙ o 2 from linear regression of V ˙ o 2 between 3 and 6 min, used to calculate the V ˙ o 2 requirement for 6 min of exercise. Panel B shows V ˙ o 2 , above rest, summed breath by breath over 6 min of exercise to determine the cumulative sum (cum sum) V ˙ o 2 . Panel C shows the V ˙ o 2 deficit (shaded) calculated by subtraction of cum sum V ˙ o 2 from the V ˙ o 2 requirement. The MRT for V ˙ o 2 is calculated from the O2 deficit and the rest to end-exercise V ˙ o 2 ; An exponential having a time a constant equal to the calculated MRT is drawn on the breath-by-breath data. CHEST 1994 105, 1693-1700DOI: (10.1378/chest.105.6.1693) Copyright © 1994 The American College of Chest Physicians Terms and Conditions

FIGURE 2 Group mean V ˙ o 2 for normal subjects and patients with CHF in response to constant work rate exercise. Each point represents mean and SE of V ˙ o 2 averaged over 30 s for subjects in each group. CHEST 1994 105, 1693-1700DOI: (10.1378/chest.105.6.1693) Copyright © 1994 The American College of Chest Physicians Terms and Conditions

FIGURE 3 Group mean V ˙ o 2 data displayed normalized as the percentage of change in V ˙ o 2 from rest to end-exercise and from end-exercise toward the pre-exercise resting value. Significance values at exercise onset refer to differences between groups from rest to the first 30-s value, approximating the phase 1 component of the onset kinetic response. Significance values during recovery refer to differences between groups from end-exercise through 2 min recovery (by multivariant analysis of variance for repeated measures). CHEST 1994 105, 1693-1700DOI: (10.1378/chest.105.6.1693) Copyright © 1994 The American College of Chest Physicians Terms and Conditions

FIGURE 4 Mean response times for V ˙ o 2 in response to constant work rate exercise for patients with CHF and normal control subjects. The MRT values were significantly longer for patients when absolute work rates of exercise (25 W and ˜60 W) were compared but are not different when identical work intensity (50 percent Δ) work rates are compared. CHEST 1994 105, 1693-1700DOI: (10.1378/chest.105.6.1693) Copyright © 1994 The American College of Chest Physicians Terms and Conditions

FIGURE 5 Comparison of MRTs for V ˙ o 2 for patients with CHF determined on two separate test days. The line of identity is drawn. CHEST 1994 105, 1693-1700DOI: (10.1378/chest.105.6.1693) Copyright © 1994 The American College of Chest Physicians Terms and Conditions