Figure 75-10 Characteristic pressure volume and flow waveforms for dual-control modes that switch the control variable "within" the breaths. A, The set tidal volume has been reached before flow has decelerated to the set flow limit; therefore, the breath continues in pressure control until the flow cycle threshold is achieved. B, The switch from pressure control to volume control occurred because flow decelerated to the set flow limit before the set tidal volume was met. This result could be caused by a decrease in patient effort or by a change in respiratory system compliance relative to the set pressure limit. (Adapted from Wilkins RL, Stoller JK, Scanlan CL: Fundamentals of Respiratory Care. St Louis, Mosby, 2003.)