Every dyspnea is a medical emergency which affords urgent treatment. In cases of an acute exacerbation of a chronic obstructive lung disease an early trial with noninvasive ventilation is recommended to avoid further deterioration which might result in intubation and invasive ventilation. In this disease invasive ventilation induces a considerably higher mortality than noninvasive ventilation. Such clear effects on mortality can not be observed in dyspnoea due to pulmonary edema in cardiac failure. However, symptoms of this disease are faster resolved by the application of positive airway pressure either through the use of chronic positive airway pressure (CPAP) or positive endexpiratory pressure (PEEP) together with pressure support using noninvasive ventilation. Thus, noninvasive ventilation has an important place in the emergency treatment in many cases of dyspnea.