Physiology of breathing and related pathological processes in infants.

There is little information describing control of breathing in the fetus and infant. The available data have largely been drawn from studies in animals and awake adults. Although the hierarchy of control of breathing is the same in adults and infants, feedback emphasis is different, with behavioral states and the sleep/wake cycle primary in the fetus and infant and integrated chemoreceptor response primary in the older child and adult. Control of breathing during the transition from the fetal state to a breathing child and the process of maturation are very different from that in adults. The article begins with an overview of the changes in the systems responsible for breathing at the developmental stages from fetus to neonate, with differences highlighted. It then discusses the possible pathology related to difficulties in negotiating this transition period, including apnea, sudden infant death syndrome, and chemoreceptor control abnormalities.