Sudden awakening from sleep can be caused by the following reasons: a. Cardiac insufficiency, if the patient has coronary heart disease, heart failure and other diseases, then the patient can have symptoms such as sudden awakening from sleep. It produces the above symptoms due to the vagus nerve excitement at night, inhibiting the contractile function of the heart, when the heart failure symptoms aggravated can appear suddenly suffocated awake in bed. Chronic renal failure, if the patient has chronic renal failure, then the kidney excretion of toxins and excess water loss of function, the accumulation of toxins in the body, excess water can not be discharged causing water and sodium retention, resulting in increased heart load, and then cardiac insufficiency and cause complications such as pulmonary edema, then kidney failure patients can appear suddenly suffocated awake at night and other symptoms. Third, sleep apnea syndrome, because the lack of oxygen during sleep may also suddenly wake up suffocating.