The research topic is to explore the effectiveness of abdominal breathing on improving of depression, anxiety, and heart rate variability in obstructive sleep apnea patients with depressive symptoms. This study method adopts an experimental research design and divided into experimental group and control group by random sampling. Experimental group receives abdominal breathing training, whereas control group without receiving abdominal breathing training.

Obstructive Sleep Apnea (OSA) is a common chronic disease with frequent comorbidity of depression. When we use sedatives, antidepressants or hypnotics for the treatment of depression, these drugs may worsen symptoms of OSA leading to aggravation of original depressed moods. Therefore, the research topic is to explore the effectiveness of abdominal breathing on improving of depression, anxiety, and heart rate variability among obstructive sleep apnea patients with depressive symptoms. This study method adopts an experimental research design and divided into experimental group and control group by random sampling. Experimental group receives abdominal breathing training, whereas control group without receiving abdominal breathing training. The research is conducted with experimental and control groups. The effectiveness assessment will use the Beck Depression Inventory (BDI) Beck Anxiety Inventory (BAI) and check the heart rate variability (HRV). Both groups received the pre-test before the abdominal breathing training. The post-test was carried out at the fourth and eighth weeks of training. The experimental group is given abdominal breathing training for a total of 8 weeks, with the training in the hospital once a week, 15 minutes for each time, in combination with self-training at home under videos guidance for 10 minutes per day (10 minutes, for one time or several times accumulated) .The expected result is through abdominal breathing, the depression, anxiety, and heart rate variability of OSA patients with depressive symptoms can improve, and even with less use of medication.

Inclusion Criteria:

• aged 20-64 years old.
• Be able to communicate with Chinese and Taiwanese, and who can express themselves without barriers.
• A person who is clearly conscious and can perform breathing exercises autonomously.
• Patients diagnosed with obstructive sleep apnea (AHI≧5) according to polysomnography and depression score ≧14 points measured by Beck Depression Inventory-II (Chinese version).

Exclusion Criteria:

• Patients with COPD.
• Patients with suicidal ideation.
• Obstructive sleep apnea AHI≧60.
• Those who have learned abdominal breathing.