1797 AUGMENTED BREATHS (SIGHS): CHANGES IN THE RELATIVE CONTRIBUTION OF THE CHEST WALL AND ABDOMEN IN INFANCY

Abstract

Electromyographic studies in animals suggest that the activation of the inspiratory intercostal muscles during augmented breaths is weaker in newborn animals compared to adults when simultaneous activation of diaphragm is compared. Since the relative contribution of these muscles during augmented breaths in neonates and children are not known, the present study was designed to determine the changes in abdominal and chest wall contribution during augmented breaths in newborn and in older infants. The abdominal and chest wall respiratory movements of ten newborn infants (<10 days) and 9 older infants (>6 weeks) were monitored by respiratory inductive plethysmograph bands. Spontaneous augmented breaths (sighs) in quiet sleep were analyzed. The control values were obtained from the mean of 3 breaths immediately preceding the augmented breath and the augmented breaths were expressed as percent of their controls. The increase in chest wall movement was smaller in newborn infants when compared to the increase in abdominal movement (173 vs 297%) whereas the increase in chest wall movement was greater in the older infants (426 vs 268%). These results suggest that the proprioceptive control of the chest wall muscles is immature in the neonatal period. This may result in poor compensation to added respiratory loads during the neonatal period. Supported by grants from the NIH (HL-01156) and the March of Dimes (5–426).