Dyspnea is a symptom resulting from a complex interaction between multiple mechanisms that are not fully understood to this day. Chronic dyspnea is defined as dyspnea lasting more than one month and this symptom is commonly seen in primary care. Cardio-respiratory pathologies account for approximately 85 % of all cases of dyspnea. Dyspnea significantly impacts the quality of life of the affected patients and is a good predictor of morbidity and mortality. Chronic dyspnea is challenging, especially when the etiology is unclear. Performing pulmonary function tests (PFTs) and a cardiopulmonary exercise test (CPET) allows to better understand the pathophysiology of the dyspnea in order to guide the diagnosis.