Figure 17-20 Relationship of functional residual capacity (FRC) to closing capacity (CC) during spontaneous ventilation, intermittent positive-pressure breathing (IPPB), and IPPB and positive end-expiratory pressure (IPPB + PEEP). See the text for an explanation of the effect of the two ventilatory maneuvers (IPPB and PEEP) on the relationship of FRC to CC. TLC, total lung capacity. The abscissa is time.