The most common reason is the occurrence of asthma, acute asthma attack, there will be a sudden breathless feeling, accompanied by breathlessness and croup. It needs to be dealt with quickly, you can nebulize inhalation bronchodilators to relieve the symptoms of sudden breathlessness, you can inhale salbutamol, terbutaline sulfate, it is best to combine glucocorticoids, such as budesonide. If the effect of nebulizer inhalation is not good, you need to go to the hospital for further examination. 2, there may be allergies, allergic factors lead to the occurrence of laryngeal edema, laryngeal edema is more serious will block the airway, the symptoms of sudden inability to breathe, is very dangerous, you need to go to the hospital or call 120. laryngitis may also appear suddenly when fast asleep edema, resulting in sudden inability to breathe. The treatment for allergy-induced laryngeal edema is the same. 3. There are also a few cases of vocal cord dysfunction, often with nocturnal attacks and breathing difficulties, which require a clear diagnosis at a specialist hospital.