[Pathophysiology of dyspnea]

The sensation of dyspnea is related to pathologically increased breathing work as a result of hyperventilation and/or increased airway resistance. Low cardiac output resulting in tissue hypoxia provokes hyperventilation. In diffuse interstitial lung diseases, hyperventilation is combined with severely reduced lung compliance. In severe airway obstruction, hypoventilation is the result of excessively enhanced breathing work. Habituation and acute changes of situation have an important bearing on the subjective sensation of dyspnea.