Sleep apnea is seen in the following cases: First, sleep apnea is seen in patients suffering from respiratory sleep apnea syndrome, who suffocate and wake up suddenly during sleep. Patients are advised to go to a sleep center to check their sleep and improve nocturnal polysomnography monitoring. Secondly, sleep apnea is seen in patients with severe carbon dioxide retention in the advanced stage of COPD, who snore very obviously and loudly at night while sleeping, and should be woken up immediately once they stop snoring, otherwise they will die of sleep apnea. Thirdly, sleep apnea at night is also seen in patients with coronary heart disease, heart failure, arrhythmia and other diseases, and it is recommended to visit cardiology department to clarify the diagnosis.