Am. J. Respir. Crit. Care Med., Vol 153, No. 2, 02 1996, 761-768.
Ventilatory responses to passive leg motion in children with congenital central hypoventilation syndrome
D Gozal, CL Marcus, SL Ward and TG Keens
Division of Neonatology and Pediatric Pulmonology, Childrens Hospital Los Angeles, California, USA.
During exercise, children with congenital central hypoventilation syndrome
(CCHS) demonstrate coupling of VE to exercise load, despite the absence of
a VE response to changes in FICO2. To assess the effect of movement on VE,
we studied six CCHS patients and six matched controls during passive motion
in a motor-driven ergocycle at pedaling frequencies (PF) of 6 to 60 rpm.
VE, VO2, VCO2, VT, heart rate, respiratory rate, SPO2, and PETCO2 were
measured. During steady-state conditions, VE was constant at PF of 0 to 30
rpm, but increased at PF > or = 40 rpm in both controls and CCHS
patients (p < 0.005). The increase in respiratory rate in CCHS patients
was greater than in controls (p < 0.05) whereas VT increased similarly
in both groups. At 60 rpm, VO2 increased in both groups, but VE/VO2 and
VE/VCO2 increased in the CCHS patients and remained constant in the
controls (P < 0.03; p < 0.04). From PF of 0 to 60, PETCO2 decreased
from 47 +/- 7 to 41 +/- 6 mm Hg in the CCHS patients (p < 0.001) but
remained unchanged in the controls (38 +/- 3 mm Hg; p = NS). An analysis of
on-transient responses at 60 rpm revealed that VE increased immediately
with the first breath after onset of motion in both groups, and that
comparable differences in ventilatory patterns persisted in the two groups.
We conclude that passive leg motion at PF > or = 40 increases VE in both
CCHS patients and controls. In controls, VE was tightly coupled to VO2 and
VCO2. However, in CCHS patients, passive leg motion elicited normalization
of PETCO2.
