Figure 2.

A-B, Elevated ventilatory dead space ratio and decreased stroke volume augmentation at anaerobic threshold and during cardiopulmonary exercise testing. Noninvasive cardiopulmonary exercise testing disclosed physiologic defects that corresponded to the patient’s dyspnea and exercise tolerance. A, Ventilatory dead space ratio (squares) at anaerobic threshold (arrow) is elevated (0.29; predicted = 0.20) and remains elevated for the remainder of exercise. B, Stroke volume augmentation at anaerobic threshold, which is estimated by the ratio of the rate of oxygen consumption/heart rate (diamonds) at anaerobic threshold (9.7 mL oxygen/beat; long arrow) to the rate of oxygen consumption/heart rate at rest (5.2 mL oxygen/beat; short arrow) multiplied by 0.55, is decreased (102%; predicted 140%). HR = heart rate; O₂-Pls = rate of oxygen consumption/heart rate; V_D/V_T = dead space proportion of tidal volume; V_T = tidal volume.