An apparatus and method for identifying the timing of the onset of and duion of an event characteristic of sleep breathing disorder. Chaotic processing techniques analyze data concerning one or more cardio-respiratory functions such as nasal air flow, chest wall effort, oxygen saturation, heart rate and heart activity. Excursions of the resulting signal beyond a threshold provide markers for the timing of such an event that is useful in the diagnosis of obstructed sleep apnea and other respiratory dysfunctions.