[Breathlessness: different causes and qualities of dyspnea]

Dyspnea is the unpleasant awareness of breathing while healthy persons will hardly sense their own breath at rest. Dyspnea is comparable to pain because both caution the organism that will activate protective mechanisms to avoid further damage. Dyspnea results from central nervous processing of respiratory feed back signals. Feed back from respiratory muscles, the chest wall, the airways and the lung reach the brain while partial pressure of oxygen and carbon dioxide is continuously monitored and arterial blood gases are permanently stabilized. Sensation of breathlessness depends on its origin. Main qualities of dyspnea include air hunger during hypercapnia, laboured breathing during increased minute ventilation and chest tightness in asthma. During chronic dyspnea, respiratory control aims for a new breathing pattern that will ease breathlessness. Since respiratory control includes both autonomic regulation and cortical modulation of breathing, voluntarily guided respiration can be employed to influence other autonomic regulated systems and pain perception.