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The diagnosis of sleep apnea


                                          Diagnosis of sleep apnea


The diagnosis of sleep apnea is based on the conjoint evaluation of clinical symptoms (e.g. excessive daytime sleepiness and fatigue) and of the results of a formal sleep study (polysomnography, or reduced channels home based test). The latter aims at establishing an "objective" diagnosis indicator linked to the quantity of apneic events per hour of sleep (Apnea Hypopnea Index(AHI), or Respiratory Disturbance Index (RDI)), associated to a formal threshold, above which a patient is considered as suffering from sleep apnea, and the severity of their sleep apnea can then be quantified. Mild OSA (Obstructive Sleep Apneas) ranges from 5 to 14.9 events per hour of sleep, moderate OSA falls in the range of 15–29.9 events per hour of sleep, and severe OSA would be a patient having over 30 events per hour of sleep.

Nevertheless, due to the number and variability in the actual symptoms and nature of apneic events (e.g., hypopnea vs apnea, central vs obstructive), the variability of patients’ physiologies, and the intrinsic imperfections of the experimental setups and methods, this field is opened to debate.Within this context, the definition of an apneic event depends on several factors (e.g. patient’s age) and account for this variability through a multi-criteria decision rule described in several, sometimes conflicting, guidelines. One example of a commonly adopted definition of an apnea (for an adult) includes a minimum 10 second interval between breaths, with either a neurological arousal (a 3-second or greater shift in EEG frequency, measured at C3, C4, O1, or O2) or a blood oxygen desaturation of 3–4% or greater, or both arousal and desaturation.