The prevalence of OSA is 3.5~4.6% in Chinese adults. OSA leads to repetitive hypoxemia, hypercapnia, and arousal from sleep and is an independent risk factor for hypertension, stroke, coronary artery disease and congestive heart failure. CPAP is the first-line treatment for OSA. But many patients do not adhere to therapy.

The upper airway(UA) anatomical abnormality is a prominent risk factor in Asian OSA patients, which might be improved by surgical strategies. However, surgery shows variable clinical effectiveness. One important reason for patients responding poorly to single treatment procedure is that multiple abnormal physiological traits contribute to OSA.

High loop gain is one of the key non-anatomical risk factors. It will be useful to individualize therapy in OSA by better understanding the reversibility of increased LG, the interaction of LG and UA anatomical change as well as the condition that trigger reduction of LG.

The project will test the hypothesis of 1) Elevated LG is induced in some patients and is reversible by treatment of OSA; 2) Change of LG is related to the improvement of sleep apnea; 3) An elevated LG is related to residual sleep apnea after upper airway surgery, which might be eliminated by adjunct CPAP therapy after surgery. The results would improve the efficiency of non-CPAP treatment and provide a potential combined treatment option for those patients with both elevated loop gain and anatomy risk factors in the Asian population.

Unstable respiratory control (high loop gain) is an important non-anatomical risk factor for obstructive sleep apnea. Studies showed high loop gain might also be acquired from long-term hypoxemia/hypercapnia due to OSA, and could be decreased by CPAP therapy in some of the individuals. Whether another treatment, i.e. upper airway surgery, could achieve a similar improvement in is not known. We hypothesize that 1) high LG could be reversible with improved hypoxemia and reduced apnea hypopnea index (AHI) by surgical treatment; 2) high loop gain at baseline may be associated with poor treatment outcomes.

PSG was performed pre- and postoperatively to assess the OSA severity in participants who underwent uvulopalatopharyngoplasty and concomitant transpalatal advancement pharyngoplasty. Loop gain were calculated using a published method by fitting a feedback control model to airflow. The loop gain values at baseline and follow-up were compared. The association between loop gain change and improvement of OSA were analyzed.

Inclusion Criteria:

• Ages 18-70 years
• Sleep study (with apnea-hypopnea index>5)
• Diagnosis of obstructive sleep apnea

Exclusion Criteria:

• Any known unstable cardiac (apart from treated hypertension), pulmonary, renal, neurologic (including epilepsy), thyroid, neuromuscular, or hepatic disease
• Pregnant women or nursing mothers
• Use of any medications that may affect sleep or breathing
• An uncontrolled psychiatric disorder
• Use of illicit drugs

Obstructive sleep apnea