Expiratory flow limitation (EFL) is defined as a dynamic condition that expiratory flow cannot be further increased with higher expiratory driving pressure. Under mechanical ventilation, it can cause intrinsic positive end-expiratory pressure (PEEP) and dynamic hyperinflation, and be associated with worse clinical outcome. The detection of EFL however needs special maneuvers and offline analysis of flow-volume curves, which are infeasible in routine practice and cannot be used during real-time monitoring. The investigators propose a new and simple approach using flow derived parameters to detect EFL in real time without needing any intervention.

Inclusion Criteria:

1. Age ≥18 years, intubated or tracheostomized
2. Receiving invasive mechanical ventilation in assist/control mode with PEEP ≥ 5 cmH2O
3. Receiving continuous intravenous sedation
4. Displaying a monotonous regular breathing pattern with no obvious asynchrony

Exclusion Criteria:

1. Severe hypoxemia in baseline clinical ventilator settings (SpO2 < 90%)
2. Hemodynamic instability (mABP <60 mmHg, systolic arterial pressure >180 mmHg, heart rate <40/min or >150/min)

Intubated patients in the intensive care unit (ICU) receiving mechanical ventilation.