Figure 2.

An example of obstructive sleep apnea (OSA). Polysomnographic example from a clinical study in a patient with severe OSA (apnea/hypopnea index = 55.5 events per hour). Note that despite the repeated respiratory efforts to breathe (thoracic and abdomen), there is no nasal airflow, indicating the airway has become obstructed. Such obstructions are often associated with repeated oxygen desaturations and arousals (gray boxes) from sleep. EKG, electrocardiogram; EEG, electroencephalogram (C3-A2); SaO₂, arterial blood oxygen saturation.