Bradley T. Thach

Impaired ventilation in infants sleeping facedown: Potential significance for sudden infant death syndrome

Although accidental suffocation has been suggested as a cause of sudden infant death syndrome in infants who are found prone with their faces straight down, the occurrence and effects on breathing of this position in living infants are unknown. We studied prone sleeping infants to see whether they will sleep with their faces straight down; whether they can spontaneously change from this position; the way that thermal stimuli or bedding softness influences this change; and whether rebreathing or airway obstruction occurs. We studied 11 healthy infants, aged 0.2 to 6 months, while they slept on soft and on firm bedding. Most infants slept facedown spontaneously or when turned to this position. All could turn their heads readily but slept facedown for variable periods. All infants put their faces straight down more often after cold than after warm stimuli. Obstructive apnea occurred only once, but rebreathing occurred in all subjects. When the infants were in the facedown position, inspired carbon dioxide was three times greater on soft than on hard bedding. End-tidal carbon dioxide partial pressure rose in all subjects while they were in the facedown position; in one infant, high end-tidal carbon dioxide partial pressure and desaturation occurred without signs of arousal. We conclude that infants sleeping facedown may occasionally have significant asphyxia; this sleep position may have a role in some infant deaths diagnosed as sudden infant death syndrome.

Graded arousal responses in infants: advantages and disadvantages of a low threshold for arousal

OBJECTIVE To review studies of upper airway protective reflexes and other aspects of arousal from sleep. METHODS Discussion of pertinent physiological studies. CONCLUSIONS Infant arousal from sleep incorporates two systems. The first comprises a group of periodically occurring reflexes serving cardiorespiratory homeostatic functions as well as providing for several aspects of normal growth and development. The second system is organized to respond to acute threats to survival during sleep. Both systems are integrated in a single arousal network originating in the brainstem. Full arousal occurs as a progression of events occurring sequentially and manifested by various innate motor and cardiovascular responses. During an arousal, rostral progression from brainstem to cortex is retarded by increasing inhibition which serves to decrease cortical arousals thereby preserving the integrity of rapid eye movement and non-rapid eye movement sleep states. Activation of brainstem arousal reflexes alone can cause recovery from obstruction sleep apnea episodes without the need for cortical arousal, a phenomenon more characteristic of infants than adults.