During which sleep stage does respiration increase and may show brief stoppages and suppressed coughing?

• A. NREM
• B. WAKE
• C. REM
• D. STAGE 2

Answer: (C)

Breathing becomes irregular during REM sleep, often speeding up with occasional brief pauses, and the muscles involved in coughing and other reflexes are suppressed due to muscle atonia. This combination—irregular respiration plus suppression of reflexes like coughing—is characteristic of REM sleep, setting it apart from NREM stages (which have steadier, more regular breathing) and Wake (which shows wakeful breathing patterns but not the same REM-associated reflex suppression).