Developmental changes in the ventilatory response of the newborn to added airway resistance.
Postnatal development of the steady-state response to inspiratory resistive loading was studied in eight 48-hour-old and seven 24-day-old tracheostomized monkeys. The newborn subjects did not maintain minute ventilation (Vl) with increasing loads of from 2 to 6 times baseline respiratory resistance, whereas the older subjects kept Vl constant when challenged by the same added resistances. The response patterns in both groups were characterized by a prolongation of Tl and Tl/Ttot, a reduction of respiratory frequency, and increases in airway occlusion pressure and respiratory work output. Apart from Vl, tidal volume (VT) was the only other ventilatory variable that differed significantly between age groups during loading. Arterial CO2 and O2 did not change from baseline in either group during loading, indicating that both age groups defended blood gas values equally well. The increases in occlusion pressures, inspiratory work output, and the maintenance of PaCO2 in the newborns indicated the presence of load compensatory mechanisms despite the fact that Vl was not strictly defended.
LaFramboise
W A
WA
Division of Neonatal and Respiratory Diseases, University of Washington, Seattle, USA..
Standaert
T A
TA
Guthrie
R D
RD
Woodrum
D E
DE
D000375:Aging / Q000502:physiology; D000403:Airway Resistance; D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D001784:Blood Gas Analysis; D001239:Inhalation; D008254:Macaca nemestrina; D008433:Mathematics; D012119:Respiration; D013990:Tidal Volume; D014939:Work of Breathing