Journal of Applied Physiology, Vol 63, Issue 4 1539-1543, Copyright © 1987 by American Physiological Society
Extrathoracic airway stability during resistive loading in preterm infants
S. Duara, T. Gerhardt and E. Bancalari
Department of Pediatrics, University of Miami School of Medicine, Florida 33101.
Extrathoracic airway (ETA) stability was tested in 10 preterm infants
during sleep with a drop in intraluminal pressure produced by the
application of an external inspiratory flow-resistive load (IRL, 125
cmH2O.1-1.s at 1 l/min). An increase in total pulmonary resistance was
sought as the measure of airway narrowing. The role of the ETA in the
increased pulmonary resistance with loading was examined by testing the
same infants while endotracheally intubated and after extubation. Total
pulmonary resistance decreased with loading during the intubated studies
(102.5 +/- 41.2 to 82.4 +/- 33.3 cmH2O.1-1.s, P less than 0.05), whereas a
significant increase in pulmonary resistance was seen with loading in the
extubated studies (101 +/- 58.1 to 128 +/- 68.6 cmH2O.1-1.s, P less than
0.01). Intraluminal pressure in the ETA, measured by the lowest proximal
airway pressure, fell significantly with loading in both conditions, with
values changing from -0.7 +/- 0.3 to -4.7 +/- 2.7 cmH2O in the intubated
infants and from -0.9 +/- 0.3 to -4.6 +/- 0.9 cmH2O) in the extubated
infants (P less than 0.01). The results suggest ETA narrowing with loading
in extubated infants despite the absence of overt obstructive apnea.
Measurements of total pulmonary resistance with IRL can be used as a simple
test of ETA stability.
