The Morphology of Periodic Breathing According to Postnatal Development

Abstract □ 101

Abstract We examined the various ventilatory morphologies of periodic breathing during quiet sleep in four groups of subjects: Group 1 (n=10, gestational age 30±1 wk, postconceptional age 32±1 wk) Group 2 (n=10, GA 31±1 wk, PCA 36±1 wk), Group 3 (n=10, GA 38±1 wk, PCA 42±1 wk), and Group 4 (n=10, weight 111±9 kg, age 50±4 yr). Respiratory pattern and ventilation were measured using a flow-through system, and sleep state was monitored. The breathing morphologies were defined according to the respiratory flow as crescendo-decrescendo, flat and decrescendo. We found: 1) a predominant crescendo-decrescendo type of breathing in preterm infants (Groups 1 and 2, >50%) and this changed to a predominant decrescendo breathing in adults (Group 4, 50%); 2) the duration of the total cycle, breathing and apneic phases did not change significantly among the neonatal groups within the same breathing morphology, 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) was higher in adults only in the crescendo-decrescendo group; 4) ventilation was highest in the middle of the breathing interval in the crescendo-decrescendo type, in the beginning of the interval in the decrescendo type, and more uniform in the flat type of breathing interval; and 5) at the beginning of each breathing interval, alveolar P_ACO₂ was highest and alveolar P_ACO₂ and O₂ saturation at lowest. The finding suggest a change in the strategy of the respiratory control system during periodic breathing between the infant and the adult, with a switch from a predominantly crescendo-decrescendo to a predominantly decrescendo pattern.