Repeated exercise-induced arterial hypoxemia in a healthy untrained woman

► An untrained woman repeatedly showing exercise-induced arterial hypoxemia. ► Exercise-induced arterial hypoxemia developed at exercise onset. ► Significant expiratory flow limitation observed at submaximal exercise intensities. ► Heliox inspiration partially reverses hypoxemia by relieving mechanical constraints. ► Mild hyperoxia maintained saturation and increased oxygen consumption.