Cardiovascular Effects After CPAP Withdrawal for Obstructive Sleep Apnea

Patients fulfilling inclusion criteria are invited to the trial after informed consent for baseline and follow-up investigations.

Baseline investigations Day 1 Patients are given a questionnaire. They are given blood pressure monitoring, (ABPM Medical 90217 ambulatory blood pressure monitor, Spacelab) for 24 hours a starting at 8-9 AM. They are also given sleep apnea recorder (Embletta, X 10 system, Embla systems, ResMed) for ambulatory use during the following night, and a container for urinary sampling during the night (urine norepinephrine).

Day 2 Fasting on arrival. Return of the 24-h blood pressure recorder, the sleep apnea recorder and the urine sampling container.

Blood samples at 08.15 am after resting for 15 minutes. Arterial stiffness is measured using arterial pulse wave velocity, radial artery applanation tonometry and office blood pressure. After resting, the measurements starts at 8.30 AM in a room with a temperature of 24°C. Pulse wave velocity (Vicorder, Skidmore Medical, Bristol, UK) is measured in the supine position. The augmentation index is derived from pulse wave analysis obtained from radial artery applanation tonometry on the right arm (SphygmoCor, AtCor Medical, Sydney, Australia).

Lung function and exhaled NO measurements, ECG. Breakfast at around 10.00 am. CPAP time counter check Patients are then randomized with a ration of 1:1 to continue with CPAP or not for the following 5 nights.

Follow-up measurements Day 6 They are given blood pressure monitoring, (ABPM Medical 90217 ambulatory blood pressure monitor, Spacelab) for 24 hours a starting at 8-9 AM. They are also given sleep apnea recorder (Embletta, X 10 system, Embla systems, ResMed) for ambulatory use during the following night, and a container for urinary sampling during the night (urine norepinephrine).

Day 7 Fasting on arrival. CPAP time counter check Return of the 24-h blood pressure recorder, the sleep apnea recorder and the urine sampling container.

Blood samples at 08.15 am after resting for 15 minutes. Arterial stiffness is measured using arterial pulse wave velocity, radial artery applanation tonometry and office blood pressure. After resting, the measurements starts at 8.30 AM in a room with a temperature of 24°C. Pulse wave velocity (Vicorder, Skidmore Medical, Bristol, UK) is measured in the supine position. The augmentation index is derived from pulse wave analysis obtained from radial artery applanation tonometry on the right arm (SphygmoCor, AtCor Medical, Sydney, Australia).

Lung function and exhaled NO measurements, ECG. Breakfast at around 10.00 am. Trials ends and patients are told to continue with CPAP as usual.

Inclusion criteria

• 18 years or older,
• given the written consent to participate in the study,
• 2 months to 2 years of continuous positive airway pressure (CPAP) treatments with good compliance (mean CPAP use of >4 hours/night) during the last month before inclusion
• moderate sleep apnea with Apnea Hypopnea Index >15 before treatment

Exclusion criteria

• Apnea hypopnea index > 10 with CPAP treatment,
• heart infarction within 3 months prior to study participation,
• severe dementia,
• determined by study personal having psychological or physical hinder to participate in the study