Unusual respiratory response to oxygen in an infant with repetitive cyanotic episodes

High inspired oxygen concentrations have recently been recommended to contr ol Cheyne-Stokes respiration in adults, with the intention of averting peri odic: apnea and its attendant arterial desaturation. We report a case study on an infant presenting with recurrent apnea and cyanosis in which oxygen treatment led to a gross form of respiratory instability we call episodic b reathing, in which a breathing phase of 60 to 90 s alternated with an apnea lasting up to 60 s. When oxygen was discontinued, a profound arterial desa turation developed before breathing recommenced and restored oxygen levels. We propose that episodic breathing is an unusual respiratory pattern that involves the central chemoreceptors and results from the ventilatory thresh old (the central PCO2 at which breathing starts) lying considerably above t he apneic threshold (the central PCO2 at which breathing stops). This featu re predisposes to lengthy periods of hyperpnea alternating with lengthy per iods of apnea. We suggest that when the case infant returned to air during episodic breathing, termination of apnea was entirely dependent upon caroti d body activity, which reached a sufficient level to restart breathing only when arterial desaturation was severe. We conclude that oxygen therapy inv olves potential risks when employed to treat respiratory disorders involvin g unstable breathing patterns in the infant.