Multiple factors contribute to exercise intolerance in patients with
sickle cell anemia, but little information exists regarding the safety of maximal cardiopulmonary exercise testing (
CPET) or the mechanisms of exercise limitation in these patients. The purpose of the present study was to examine these issues. Seventeen adult women with
sickle cell anemia underwent symptom-limited maximal
CPET using cycle ergometry and ramp protocols; blood
gases and
lactate concentrations were measured every 2 minutes. All patients completed
CPET without complications. No patient demonstrated a mechanical ventilatory limitation to exercise or had evidence of
myocardial ischemia. However, we observed three pathophysiologic patterns of response to exercise in these patients. Eleven patients had low peak VO2, low anaerobic threshold (AT), gas exchange abnormalities, and high ventilatory reserve; this pattern is consistent with exercise limitation due to pulmonary
vascular disease in this patient subgroup. Three patients had low peak VO2, low AT, no gas exchange abnormalities, and a high heart rate reserve, a pattern consistent with
peripheral vascular disease and/or a
myopathy. The remaining three patients had low peak VO2, low AT, no gas exchange abnormalities, and a low heart rate reserve; this pattern of exercise limitation is best explained by
anemia.