Arterial blood gas levels obtained with tidal volume of 550 mL, positive end-expiratory pressure (PEEP) of 5 cm H2O, 50% oxygen, and volume control ventilation at 15 breaths/min were as follows: pH, 7.26; Paco2, 37 mm Hg; Pao2, 135 mm Hg; and Paco2, 16 mm Hg. The patient’s peak airway pressure was 58 cm H2O, and her arterial lactate level was 8.0 mEq/L. The ventilator was changed to a pressure control mode for fear of causing bronchial stump blowout because of increasing airway pressures. The next set of arterial blood gas levels, obtained with settings of pressure control at 35 mm, a respiratory rate of 15 breaths/min, a tidal volume of 440 mL, and a fraction of inspired oxygen of 50% oxygen with PEEP set at 3 cm H2O, but auto-PEEP set to 11 cm H2O, were as follows: pH, 7.02; Paco2, 62 mm Hg; Pao2, 93 mm Hg. Her minute ventilation on both modes remained similar. Her static compliance was calculated at 60 cm H2O, and her dynamic compliance was 25 cm H2O. Because of worsening acidosis and hypotension, a mixed venous gas was obtained with a pH of 7.21, a mixed venous oxygen pressure of 33 mm Hg, a mixed venous saturation of 59%, and a base deficit of 7.6 mEq/L. Additional fluid resuscitation for her worsening status was undertaken with 4 U packed RBCs and 4 L crystalloid.