The morphology of periodic breathing in infants and adults

To test the hypothesis that the crescendo–decrescendo type of pattern of periodic breathing is more common in infants than in adulthood, we examined the morphologies of periodic breathing in four groups of subjects: group 1 (n=10, gestational age 30±1 week), group 2 (n=10, GA 31±1 week), group 3 (n=10, GA 38±1 week), and group 4 (n=10, age 50±4 years). Respiratory pattern and ventilation were measured using a flow-through system. The breathing morphologies were defined according to the respiratory flow. We found (1) a predominant crescendo–decrescendo pattern in preterm infants (groups 1 and 2, >50%) and this changed to a predominant decrescendo breathing in adults (group 4, 50%); (2) total breathing cycle and its phases did not change significantly among the neonatal groups, but they almost doubled in adult subjects; however, the number of breaths per breathing interval remained the same (crescendo–decrescendo) or less (flat and decrescendo) in adults as compared to preterm infants; (3) the duty cycle (breathing interval/cycle duration) remained consistent with age; and (4) at the beginning of each breathing interval, alveolar P_co2 was highest and alveolar P_o2 and O₂ saturation lowest. The findings suggest a change in the strategy of the respiratory control system during periodic breathing between the infant and the adult, perhaps dictated by mechanical and chemoreceptor limitations early in age, with a switch from a crescendo–decrescendo to a predominantly decrescendo pattern.