Sustained high inspiratory pressures during positive-pressure ventilation increase the risk of:

Intermittent or sustained high inspiratory pressures (>30 mm Hg) during positive-pressure ventilation increase the risk of pulmonary barotrauma (eg, pneumothorax) or hemodynamic compromise, or both, during anesthesia, Excessively high pressures may arise from incorrect settings on the ventilator, ventilator malfunction, fresh gas flow coupling, or activation of the oxygen flush during the inspiratory phase of the ventilator. Use of the oxygen flush valve during the inspiratory cycle of a ventilator must be avoided because the ventilator spill valve will be closed and the APL valve is excluded; the surge of oxygen (600-1200 mL/s) and circuit pressure will be transferred to the patient's lungs. Ref: Butterwoh IV J.F., Butterwoh IV J.F., Mackey D.C., Wasnick J.D., Mackey D.C., Wasnick J.D. (2013). Chapter 4. The Anesthesia Machine. In J.F. Butterwoh IV, J.F. Butterwoh IV, D.C. Mackey, J.D. Wasnick, D.C. Mackey, J.D. Wasnick (Eds), Morgan & Mikhail's Clinical Anesthesiology, 5e.