Am. J. Respir. Crit. Care Med.,
Volume 159, Number 2, February 1999, 389-396
Partitioning of Respiratory System Resistance in
Children with Respiratory Insufficiency
ATHANASIOS G.
KADITIS,
SHEKHAR T.
VENKATARAMAN,
WALTER A.
ZIN,
and
ETSURO K.
MOTOYAMA
Departments of Pediatrics (Division of Pediatric Pulmonology) and Anesthesiology and Critical Care Medicine, University of
Pittsburgh School of Medicine and Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania; and Institute of Biophysics,
Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
Using end-inspiratory airway occlusion, respiratory system resistance (Rrs) can be partitioned into a
flow-resistive component (Rint), and an additional component (
R), reflecting viscoelasticity and time
constant inequalities. We studied flow and volume dependence of Rrs and its subdivisions (Rint and
R) in 13 children, seven mechanically ventilated for pulmonary insufficiency (Group 1; six with parenchymal lung disease; one with lower airway obstruction) and six without primary lung disorder
(Group 2). In comparison with healthy children, Rint was increased in the patient with lower airway
obstruction and five of six patients without primary lung disorder but in only one of six with parenchymal lung disease. R was increased in all seven patients in Group 1 and in four of six patients in
Group 2. The directions of changes in Rint and Rrs with increasing flow (isovolume conditions) and
with increasing volume (isoflow conditions) were variable. R decreased exponentially (p < 0.05)
with increasing flow in 11 of 13 subjects and increased with increasing tidal volume (VT) in 12 of 13. Thus, R was increased in most children on mechanical ventilation with or without primary lung disease; its volume and flow dependence were opposite to that of airway resistance.
