Diaphragm Ultrasound-Guided PEEP Titration in COPD with Dynamic Hyperinflation

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation, dynamic hyperinflation, and intrinsic positive end-expiratory pressure (iPEEP), which increase inspiratory threshold load and complicate ventilatory support. Non-invasive ventilation (NIV) is the preferred initial ventilatory support for COPD exacerbations complicated by acute or acute-on-chronic respiratory acidosis, while invasive mechanical ventilation (IMV) may be required when NIV fails. External PEEP may reduce the inspiratory threshold load in patients with expiratory flow limitation, although excessive levels can increase lung volume and compromise hemodynamics. During IMV, PEEP adjustment requires assessment of respiratory mechanics, expiratory flow, hyperinflation, and cardiovascular tolerance. During NIV, where iPEEP cannot usually be measured directly, expiratory positive airway pressure (EPAP) should be adjusted according to clinical response, patient-ventilator interaction, and signs of excessive lung inflation. Inappropriate ventilatory assistance may also contribute to diaphragm dysfunction. Diaphragm ultrasound allows bedside assessment of muscle thickness and inspiratory thickening fraction (DTF), although these measurements are influenced by ventilatory assistance, respiratory drive, and lung volume. This review examines the physiological basis, available evidence, and limitations of using diaphragm ultrasound to complement PEEP adjustment in patients with COPD and dynamic hyperinflation. No DTF target or clinical benefit of ultrasound-guided PEEP titration has been established in this population.