Tracings of respiratory variables (capnogram: carbon dioxide concentration; flow: respiratory flow; airway pressure [P_AW]; tidal volume [TV]) during one-hand mask ventilation (MV) showing three different expiratory flow patterns and influences of two-hand MV on the respiration. The images were taken from the cardiorespiratory monitor, and the vertical dotted lines denote beginnings of tracings. Note the three different flow patterns. (A) Normal flow pattern without difference between inspiratory and expiratory TV (expiratory flow limitation [EFL]-1) in a non–sleep-disordered breathing (SDB) subject. (B, D) EFL-2, characterized by abrupt expiratory flow reduction immediately after peak expiratory flow, with smaller expiratory TV than inspiratory TV in SDB patients. (C) More severe EFL-3 with smaller TV during both inspiration and expiration in a SDB patient. Note the reversal of expiratory flow limitation and significant TV increase during two-hand MV in the cases (B) and (C) but not in the case (D). Capnogram waveforms were classified in accordance with the 2014 JSA airway guideline ventilation (reference 12). ET CO₂ = end-tidal carbon dioxide concentration; flow = flow rate measured by pneumotachograph; V1 = normal capnogram with the presence of phase III; V2 = subnormal capnogram with the presence of phase II but lack of phase III; V3 = abnormal capnogram without capnogram waveform.