Figure 1.

Displays of concurrent 90-s averages of O₂ uptake and CO₂ output, both divided by exhaled ventilation (–versus–) during cardiopulmonary exercise testing from rest through early recovery, with “+” and “×” showing transitions between rest and exercise and exercise and recovery. Vertical and horizontal dashed lines are reference highest and highest . A, Healthy 38-year-old man with peak 106% of predicted. B, Healthy 52-year-old woman with peak 101% of predicted. Note that with exercise, both numerators increase more than denominators until reaching highest and then highest before rapid declines, especially in values, during high-intensity exercise and recovery. C, Fifty-seven-year-old woman (NYHA Class II) with moderate left heart failure, oscillatory breathing, and peak 63% of predicted. The shape of the early exercise pattern is reasonable, but the highest and are well below normal. The rise in during the transition to recovery is abnormal. D, Seventy-three-year-old man (NYHA class IV) with peak 21% of predicted who died several weeks later. All values are very low. The resting, exercise, and recovery values overlay each other and on magnification can be seen to oscillate. Immediate movement to the lower left at the onset of exercise is an ominous pattern. E and F, Left heart failure in 64-year-old man before and after treatment. Raw data were obtained every 30 s rather than 10 s. In E, values move to the left ( is decreasing) and upward with exercise. After treatment, peak values increased from 45% to 66% of predicted. In F, resting values start higher and move upward and to the right (indicating is also increasing) before moving leftward. In both studies, the highest occurred when ≈21 L/min, at which time was 25×21=≈520 mL/min (E) and was 370×21=≈780 mL/min (F). Thus, this 50% increase in from E to F was primarily due to increased perfusion, not increased ventilation.