Breathlessness in the middle of the day may be caused by the following diseases, such as obstructive sleep apnea hypopnea syndrome, heart failure, reflux esophagitis and so on. 1. Obstructive sleep apnea hypopnea syndrome: with sleep snoring, apnea and daytime sleepiness as the main manifestations, there will be repeated collapse of the airway, so it will produce the phenomenon of inhalation and suffocation in the middle of the day. 2. Heart failure: especially in patients with left heart failure, there will be pulmonary stasis, dyspnea, increased return of blood during sleep, and inhalation and breath-holding at noon due to insufficient pulmonary ventilation. 3. reflux esophagitis: severe reflux esophagitis due to reflux stimulation of the trachea, will also appear in the midday sleep up inhalation breath holding, at the same time there is acid reflux, heartburn and other discomforts. There are more reasons for breathlessness in the middle of the day, such as lung infection, lung tumors, pneumothorax and other diseases, patients should consult a doctor in time to clarify the cause of the disease, early treatment, so as not to delay the condition.