A Review Study of Causes of Sudden Infant Death Syndrome.

Purpose: The Sudden Infant Death Syndrome (SIDS) is the unexpected death of an apparently healthy infant for which no reason can be found after a postmortem examination. The primary causes of SIDS have not been determined. The purpose of this study was to examine the primary causes of this syndrome by reviewing the research results and new theories and in view of recent experimental findings.

Methods: The theories on SIDS were reviewed. The results of computer simulations of this disorder using an isomorphic model that were published in the past were compared to new experimental results and hypotheses.

Results: The most important factors contributing to periodic breathing and prolonged apneic spells in infants were confirmed to be the factors related to the development of the respiratory control system, including the maturity factors of arterial and central receptors in response to carbon dioxide, the maturity factor of arterial receptors to oxygen, as well as the lung functional residual capacity (FRC), which is affected by the infant's age. The lung shunt ratio in preterm infants and poor gas exchange in the lungs were also significant factors, but to a lesser degree.

Conclusion: SIDS is primarily caused by the prematurity of arterial and central respiratory receptors during a developmental period and the size of FRC. Infants who are at high risk of SIDS may be monitored using pulse oximetry during sleep. Low oxygen levels in those infants can be detected and trigger an alarm, which may save the lives of those infants.