Figure 6.

Percentage change in tidal volume during NREM and REM sleep. The percentage change in tidal volume (V_T) during nonrapid eye movement (NREM) and rapid eye movement (REM) sleep is shown for the 3 groups. See Figure 1 for a description of the box plots. During NREM sleep, study participants with obstructive sleep apnea syndrome (OSAS) had a lower percentage change in V_T in response to CO₂ than those in the control groups. During REM sleep, those in the OSAS group had a lower percentage change in V_T than those in the lean control group.