It is difficult to separate clinical manifestations of apnea from consequences of apnea. Symptoms and signs depend on the duration and frequency of apnea and most are related to hypoxia. Other clinical manifestations depend on the etiology of apnea such as feeding intolerance, lethargy, temperature instability, jitteriness, poor feeding, central nervous system (CNS) depression, irritability, desaturation, tachypnea, tachycardia, bradycardia, hypotonia, and seizures.