Dyspnea By Rebecca Dezube, MD, MHS, Johns Hopkins University Reviewed / Revised Sep 2021 | Modified Sep 2022 View Patient Education Pathophysiology Etiology Evaluation Treatment Key Points Topic Resources A-a Gradient Some Causes of Acute * Dyspnea Some Causes of Subacute *... Some Causes of Chronic * Dyspnea Dyspnea is unpleasant or uncomfortable breathing.