[Pulmonary function in preterm and full term infants during the neonatal period: 1. respiratory pattern]

The pattern of breathing of 18 preterm newborn infants weighing less than 1500 g. at birth, and old 35 full-term newborns weighing more than 2500 g. at birth were studied during the neonatal period. The newborns were grouped according to postnatal age. (less than 24 hrs; 24 hrs.-7 days and less than 7 days). The inspiratory and expiratory flow was measured by means of pneumotachography. The respiratory rate values (f) decrease with postnatal age: The highest values in all three postnatal age groups correspond to the preterm newborns. The decrease in is a accompanied by an increase in the duration of inspiratory (TI) and expiratory (TE) time to such and degree that the relationship TI/total respiratory cycle (TI/TTOT) shows no significant differences between the groups studied. Both in preterm and full-term newborns, the peak expiratory flow occurs at a later point in expiration during the first 24 hours of life. The tidal volume (VT) and the minute ventilation increase with age. The VT in proportionate to the weight in all groups. The mean inspiratory flow (VT/TI) is lower in the preterm newborns, and within each group, the values are higher in those whose postnatal age is greater.