CPAP treatment provides effective physical pressure support to the upper airway of patients with OSAHS, restoring normal sleep structure, apnea hypoventilation index (AHI) to normal levels, and normalizing sleep state oxygen saturation and partial pressure of carbon dioxide, thereby eliminating a series of pathophysiological changes in patients. 1.Improve sleep structure and quality During the first night of treatment, within seconds of ensuring the patency of the upper airway, patients with severe sleep apnea begin prolonged REM phase and NREM4 phase sleep, and this rebound period during recovery from severe fragmented sleep takes about 1 week; the duration and intensity of this rebound sleep period decreases significantly after the first night of treatment. The intensity and even the nature of the neurophysiological and neurochemical mechanisms occurring during the first few nights of rebound sleep differ compared to normal sleep in subsequent long-term CPAP treatment. REM sleep in the rebound period differs from normal REM due to the presence of an extremely long REM phase (often 1-2 hours of uninterrupted REM sleep and high density of fast-acting eye phases.) NRM stage 4 sleep is predominantly hypertensive and slow-wave, even in older cases (where stage 4 sleep is rare under normal conditions). It is possible that significantly expanded neurochemical processes cause these changes. Investigation of patients and application of the multiple daytime nap latency test (MSLT) confirmed the strong short- and long-term effects of CPAP on stopping daytime sleepiness, and the disappearance of sleepiness was also indicated by significantly improved results of the practical maneuverability test. 2. Psychological effects OSAHS patients often have endocrine dysfunction. By observing patients after CPAP treatment, it was found that indicators such as cognitive ability, memory and attention improved significantly. 3. Hormonal effect studies have shown that OSAHS patients have endocrine dysfunction and their testosterone and growth-promoting factor C (insulin-like growth factor 1) levels are suppressed to a degree that correlates with the severity of the disease. This impairment was reversed after 3 months of CPAP application with no change in body weight. Growth factor C levels reflect 24-hour growth hormone secretion. decreased levels of growth factor C in patients with OSAHS and its normalization after CPAP treatment may explain the accelerated growth in pediatric OSA patients. There is now increasing evidence that growth hormone may be beneficial in the elderly. Decreased testosterone levels may be closely related to the loss of erectile capacity in OSAHS patients. Sexual function is significantly enhanced in patients treated with CPAP. CPAP therapy can regulate leptin secretion and normalize fat metabolism in patients with OSAHS. 4. Effects on upper airway and respiratory function CPAP improves the structure of oropharyngeal airway tissue. The patient’s soft palate is overgrown, swollen, appears erythematous and obviously edematous as mechanical trauma caused by snoring. After CPAP treatment these changes are improved, the swelling, erythema and edema subside, and the soft palate returns to normal pink color from the congestion and swelling manifestation common before treatment; long-term observation and analysis show that CPAP has no harmful effect on pulmonary function and no change in the diffusion function of carbon dioxide. The effect of CPAP on cardiovascular function is particularly significant in OSA patients with right heart failure or severe hypertension, and the long-term application of CPAP improves cardiovascular function, with rapid diuresis and disappearance of peripheral edema in patients with right heart failure. In patients with combined coronary artery supply deficiency and hypertension, blood pressure normalized after CPAP treatment and cardiac function improved. After 3-12 months of regular nocturnal treatment, most patients improve significantly and then enter a stable phase of efficacy, which generally requires lifelong adherence to treatment.