[How I explore … diaphragmatic dysfunction].

Diaphragmatic dysfunction, whether unilateral or bilateral, partial or complete, is often an overlooked cause of dyspnea, sleep disturbances, and, in more advanced stages, chronic alveolar hypoventilation. It may result from injury to the phrenic nerve, the diaphragm muscle itself, or central nervous system pathways. The diagnosis is frequently suspected when an elevated hemidiaphragm is incidentally observed on chest imaging. A comprehensive assessment combining clinical examination, pulmonary function tests, arterial blood gas analysis, and targeted imaging is essential to confirm the dysfunction, identify its underlying cause, evaluate its severity, and guide management. In its advanced form, chronic hypercapnic respiratory failure may occur, often requiring non-invasive ventilation in addition to treatment of the underlying cause. This review outlines a structured and practical approach to the evaluation of diaphragmatic dysfunction, incorporating recent advances and key clinical considerations.