Etiology: Sleep apnea hypoventilation syndrome is a recurrent apnea or a significant decrease in oral and nasal airflow due to collapse of the pharyngeal muscles blocking the airway during sleep. It is classified into three types: obstructive, central and mixed, with obstructive sleep apnea hypoventilation syndrome (OSAHS) being the most common, accounting for about 8%-9O% of SAHS, and is an important cause of intractable hypertension; at least 30% of hypertensive patients have OSAHS in combination, and the incidence of hypertension in OSAHS patients is as high as 5O-8O%. Diagnosis: Clinical manifestations: 1. snoring at night, snoring – airflow stop – gasping alternately, serious cases can be suffocated awake; 2. abnormal sleep behavior, manifested as night shrieking fear, murmuring, night wandering; 3. daytime drowsiness, headache, dizziness, weakness, serious cases can fall asleep at any time, some patients have abnormal mental behavior, inattention, memory and judgment loss, dementia, etc.; 4. personality changes, irritability, agitation, anxiety, and some patients may have hypersexuality and impotence. Patients mostly have obesity, short neck, nasal polyps, enlarged turbinates, tonsils and uvula, low hanging soft palate, narrowed pharyngeal cavity, enlarged tongue, receding mandible and small jaw deformity, OSAHS can often cause hypertension, arrhythmia, acute myocardial infarction and other cardiovascular diseases. Polysomnography is the “gold standard” for the diagnosis of OSAHS. In 7h of sleep per night, apnea and hypoventilation are repeated more than 3O times and/or the apnea hypoventilation index is ≥5 times/h (apnea is defined as the cessation of nasal and oral airflow for more than 1 Os, and hypoventilation is defined as the reduction of respiratory airflow to less than 50% of the basal value with a decrease in oxygen saturation of more than 4%). The apnea hypoventilation index (AHI) and nocturnal SaO2 values are classified as mild, moderate or severe, with AHI 5-2O and minimum SaO2 ≥ 86% as mild, AHI 21-6O and minimum SaO2 8O%-85% as moderate, and AHI > 6O and minimum SaO2 < 79% as severe. Treatment: Weight reduction and lifestyle changes are important for OSAHS, oral appliances are effective for mild and moderate OSAHS, CPAP is often required for moderate and severe OSAHS, attention is paid to the selection of appropriate antihypertensive drugs, and appropriate surgical treatment can be considered for patients with anatomical abnormalities of the nose, pharynx, palate and jaw.