The sleep apnea hypopnea syndrome (SAHS) is a respiratory disorder characterized by frequent breathing cessations (apneas) or partial collapses (hypopneas) during sleep. These respiratory events lead to deep oxygen desaturations, blood pressure and heart rate acute changes, increased sympathetic activity and cortical arousals. The gold standard method for SAHS diagnosis is in-hospital, technician-attended overnight polysomnography (PSG). However, this methodology is labor-intensive, expensive and time-consuming, which has led to large waiting lists, delaying diagnosis and treatment. Blood oxygen saturation (SpO2) from nocturnal pulse oximetry (NPO) provides relevant information to detect apneas, it can be easily recorded ambulatory and it is less expensive and highly reliable. The investigators hypothesize that an automatic analysis of single oximetric recordings at home could provide essential information on the diagnosis of SAHS. The aim of this study is two-fold: firstly, the research focuses on assessing the reliability and usefulness of NPO carried out at patient's home in the context of SAHS detection and, secondly, the study aims at assessing the performance of an automatic regression model of the AHI by means of neural networks using information from NPO recordings. To achieve this goal, both PSG and NPO studies are carried out. A polysomnography equipment (E-Series, Compumedics) is used for standard in-hospital PSG studies, whereas a portable pulseoximeter (WristOX2 3150, Nonin) is used for ambulatory NPO. NPO is carried out the day immediately before or after the PSG at patient's home. Patients are assigned to carry out the NPO study before or after the in-hospital PSG randomly. In addition, in-hospital attended oximetry is also performed simultaneously to the PSG using the portable pulseoximeter.