Obstructive sleep apnea (OSA) is a highly prevalent sleep-disordered breathing disease, caused by recurrent episodes of partial or complete collapse of the upper airway during sleep, resulting in intermittent hypoxia, fragmented sleep, fluctuations in blood pressure, and increased sympathetic nervous system activity. A single-night sleep study (i.e. respiratory polygraphy or polysomnography) is currently considered to be the gold standard for diagnosing OSA. However, recent studies suggest a significant intra-individual night-to-night variability of respiratory events, leading to the hypothesis that one single-night study might not reflect an accurate picture of the disease.

Part A: Patients with suspected obstructive sleep apnea, referred to our clinic, undergo the regular diagnostic procedure recommended by the current guidelines. In addition to the in-hospital single-night sleep study, these patients will perform 14 nights of pulse-oximetry at home. By computing and analysing sensitivity and specificity of every additional night, the investigator will answer the questions how many nights of sleep monitoring by home oximetry are necessary to diagnose OSA reliably, and how longitudinal sleep monitoring could reduce the number of false-negative and false- positive results compared to the in-hospital single-night study.

Part B: Based on the patients' data of part A, the investigator will develop a questionnaire and present anonymized cases to experts in the field of sleep medicine. Thereby, the investigator will evaluate if the additional information of repeated nocturnal pulse-oximetries changes the experts' decision making regarding diagnosis and treatment of OSA.

In a second step, the investigator will perform a classical Delphi study with a panel of experts in sleep medicine to establish consensus on repeated sleep studies and how they should be used for diagnosis and treatment in patients with suspected OSA.

Inclusion Criteria:

• Informed consent
• Suspected obstructive sleep apnea
• ≥18 years old

Exclusion Criteria:

• Suspected or diagnosed sleeping-disordered breathing other than OSA
• Moribund or severe disease prohibiting protocol adherence especially COPD GOLD III-IV and heart failure NYHA III-IV
• Patients receiving oxygen therapy or home ventilation
• Continuous positive airway pressure treatment for OSA at baseline
• Physical or intellectual impairment precluding informed consent or protocol adherence
• Pregnant patients

Patients with suspected obstructive sleep apnea

on reasonable request only