Little is known of the final physiologic mechanism(s) resulting in SIDS. Five infants participated in this study, three of whom were referred at about 1 month of age because of cyanotic episodes of undetermined etiology. Respirations and eye movements were recorded during several sleep sessions on each patient. In addition, patients were observed on an apnea monitor and a record was kept of the incidence of prolonged apneic episodes (≥ 15 seconds).
The laboratory sleep studies revealed frequent periods of apnea (≥ 2 seconds) which (1) decreased in amount after a certain age and (2) were most frequent during REM sleep. All infants had a number of prolonged apneic and cyanotic episodes during sleep, some requiring vigorous resuscitative efforts. Prolonged apnea most often occurred in conjunction with an upper-respiratory tract infection or when frequent apnea was noted in the laboratory. Two of the infants subsequently died of SIDS.
These data support the hypothesis that prolonged apnea, a physiological component of sleep, is part of the final pathway resulting in sudden death. It is suggested also, that infants at risk might be identified prior to the final tragic event.