Final answer:
Central apnea is present when both nasal flow and respiratory effort decrease, associated with issues in the brain's respiratory centers or certain medications and sharing symptoms like fatigue with obstructive sleep apnea.
Step-by-step explanation:
If both nasal flow and respiratory effort decrease, the type of apnea present is central apnea. In central sleep apnea, the respiratory centers of the brain fail to respond to rising carbon dioxide levels, which means they don't regularly stimulate the muscles necessary for breathing. As a result, there is a cessation of breathing during sleep. This is different from obstructive sleep apnea, where the airway is physically blocked, preventing air from entering the lungs. Central sleep apnea can be associated with medical conditions affecting the brain's respiratory centers or by the use of certain pharmacologic agents. Symptoms include those similar to obstructive sleep apnea such as fatigue and morning headaches.