Figure 3.

CO₂ Challenge in a Lean Control Subject during NREM Sleep. A 3-min epoch from a 12-yr-old boy in the lean control group during non-rapid eye movement (NREM) sleep is shown. After administration of CO₂ (arrow), the study participants had an increase in air flow. Y-axis parameters: C3-M2, C4-M1, O1-M2, and O2-M1 are electroencephalogram leads; E1-M2 and E2-M1 are left and right electrooculograms, respectively; Chin electromyogram (EMG), submental EMG signal; pneumotach flow, airflow measured with a heated pneumotachometer; ETCO₂, end-tidal PCO₂ value; TCCO₂, transcutaneous PCO₂; time axis, clock time (in sec).