How long does apnoea in premature infants lasts for?

Apnea is defined as cessation of respiration for 20 seconds with or without bradycardia and cyanosis or for shoer periods if it is associated with cyanosis or bradycardia. It is usually seen in preterm neonates. Apnea could be of three types central, obstructive or mixed type: Central apnea is characterized by the absence of diaphragmatic activity. Obstructive apnea is characterized by upper airway obstruction with persistent diaphragmatic activity. Mixed apnea has features of both central and obstructive types. Central and mixed types are the most common types of apnea that occur in premature infants. Ref: Respiratory Control and Disorders in the Newborn By Oomen P. Mathew page 115.