Physiological Effects of External PEEP in Controlled Mechanical Ventiated Patients With autoPEEP

This experimental physiologic study is conducted to determine the effect of different mechanical ventilation settings (in terms of positive end-expiratory pressure) on patients receiving mechanical ventilation with expiratory flow obstruction and autoPEEP. The main question it aims to answer In patients with autoPEEP, what is the effect of applying external PEEP on gas exchange and the lung emptying pattern in patients with total ventilatory support? Participants must comply: \- Age \> 17 years. * Invasive mechanical ventilation (endotracheal tube or tracheostomy) in controlled mode, with SpO2 \> 90%, for more than 12 hours. * No contraindications for abdominal compression. * Presence of autoPEEP greater than 3 cmH2O measured in mechanical ventilation with total support and ZEEP. * Total mechanical respiratory support, without respiratory muscle activity (inspiratory or expiratory).