Sleep Apnea in Frail Elderly

Main goal: to define the more specific and sensitive cut-off of variability index of the oximetry to detect sleep apnea in the hospitalized elderly. Secondary goals: * sleep apnea prevalence in the elderly * accuracy of other oximetry parameters (saturation line, oximetry desaturation index, autonomic arousals) for detection of respiratory disturbances in sleep apnea in the hospitalized elderly * to determine the clinical and biological data associated with sleep apnea in the hospitalized elderly * to determine the factors associated with the record failures and its prevalence * to study the prevalence of the Periodic Limb Movements of Sleep in the hospitalized elderly Study design: simultaneous records by oximetry and ventilatory polygraphy with tibial EMG in the hospitalized elderly in a geriatric readaptation unit.