Corrigendum: Oxygen Extraction Based on Inspiratory and Expiratory Gas Analysis Identifies Ventilatory Inefficiency in Chronic Obstructive Pulmonary Disease - Miki, Keisuke; Tsujino, Kazuyuki; Maekura, Ryoji; Matsuki, Takanori; Miki, Mari; Hashimoto, Hisako; Kagawa, Hiroyuki; Kawasaki, Takahiro; Kuge, Tomoki; Kida, Hiroshi (Frontiers in Physiology, 2021)