Fig. 4.
Photographs of anesthesia ventilator screens during robotic abdominal hysterectomy; abdomen is insufflated, position steep Trendelenburg; traces are of airway pressure over time. Measured variables are in yellow over black background, set variables in black over yellow. (A) Volume control constant flow ventilation; note peak inspiratory pressure (Pmax) of 30 cm H2O. (B) Same mode of ventilation with end-inspiratory pause of 50% of inspiratory time. Note the higher Pmax (34 cm H2O) generated by the higher inspiratory flow necessary to compensate for the pause in inspiratory flow. Tidal volume (Vte) remained the same, and plateau pressure (Ppl-50%, 28 cm H2O) nearly the same as the Pmax prior to inducing the inspiratory pause. (C) Pressure control ventilation set to generate the same Vte is nearly equal to Ppl-50%, indicating that (1) with pressure control, the peak inspiratory pressure (Pmax in the figure) is the plateau pressure; and (2) the pressure that generates a certain tidal volume, which is the plateau pressure, is nearly the same in all three conditions. E, minute ventilation.