Objective: To assess whether the delivered nitric oxide (NO) concentration
is affected by a change in the ventilatory setting during neonatal mechanic
al ventilatory support.
Design: Prospective, experimental study.
Setting: Laboratory at Nagoya City University Medical School.
Interventions: This study was performed by using a pressure-limited, time-c
ycled, ventilatory support with a neonatal circuit and a 50-mL silicone tes
t lung. NO in N-2 gas was administrated into the inspiratory limb at a dist
ance of 4 cm, 80 cm, or 160 cm from the Y piece connected to the adapter of
an endotracheal tube. The NO concentration was measured every 0.5 sec by a
chemiluminescence analyzer at the Y piece.
Measurement and Main Results: NO concentrations were compared with each of
the ventilatory settings of peak inspiratory pressure (PIP) (10-30 cm H2O),
positive end-expiratory pressure (0-10 cm H2O), ventilatory flow (10, 20,
30 L/min), and ventilatory rate (30, 40, 50, 60, 70 breaths/min), respectiv
ely. The NO concentration was significantly lower when NO was added at 4 cm
than at 80 cm or 160 cm from Y piece at the same ventilatory setting of PI
P, positive end-expiratory pressure and ventilatory flow, respectively, (p
< .01), Although the NO concentration was increased as the settled PIP leve
l was increased (p < .01 or p < .05), it was not changed when the settled p
ositive end-expiratory pressure level was increased. A decrease was seen in
the NO concentration as the settled ventilatory flow was increased (p < .0
1), Lastly, the NO concentration fluctuated greatly in association with the
settled ventilatory rate.
Conclusion: The NO concentration delivered to patients is influenced by the
ventilatory setting during neonatal mechanical ventilatory support.