5,6 Adenosine is a nucleoside component of compounds such as adenosine triphosphate (ATP) and cyclic adenosine monophosphate (cAMP), which are crucial to numerous biochemical processes. One theory describes the role of adenosine as a central respiratory inhibitor. Several theories exist regarding the pathogenesis of AOP, none of which have been confirmed as being the single cause to date. 3 Studies have shown that the majority of apnea events (~50%) in preterm infants are of mixed origin, 40% are of central origin, and 10% are purely obstructive in origin. 2 Mixed-type apnea is a combination of both central and obstructive apneas. Obstructive apnea, most commonly due to collapse of the pharyngeal airway, results in mechanical interference with respiratory efforts and often leads to bradycardia. (The different types of apnea and periodic breathing are categorized in TABLE 1.) Central apnea refers to the failure of the central CNS to initiate respiratory effort secondary to immaturity of the neurologic pathways. Periodic breathing represents a normal occurrence of breathing during sleep and is often confused with apnea. 1 The apnea can be classified as being of central origin, obstructive, or mixed type. It is a diagnosis of exclusion that can only be confirmed once alternate causes of apnea (e.g., sepsis, metabolic disorders, central nervous system pathology) have been excluded. Apnea of prematurity (AOP) commonly occurs in infants of less than 37 weeks’ gestation and is characterized by brief episodes of breathing cessation lasting 20 seconds or less with associated bradycardia or cyanosis.
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