During neonatal mechanical ventilatory support, the delivered nitric oxide concentration is affected by the ventilatory setting.

Abstract

To assess whether the delivered nitric oxide (NO) concentration is affected by a change in the ventilatory setting during neonatal mechanical ventilatory support. Prospective, experimental study. Laboratory at Nagoya City University Medical School. This study was performed by using a pressure-limited, time-cycled, ventilatory support with a neonatal circuit and a 50-mL silicone test lung. NO in N2 gas was administrated into the inspiratory limb at a distance 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. 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), respectively. 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 PIP, positive end-expiratory pressure and ventilatory flow, respectively, (p < .01). Although the NO concentration was increased as the settled PIP level was increased (p < .01 or p < .05), it was not changed when the settled positive end-expiratory pressure level was increased. A decrease was seen in the NO concentration as the settled ventilatory flow was increased (p < .01). Lastly, the NO concentration fluctuated greatly in association with the settled ventilatory rate. The NO concentration delivered to patients is influenced by the ventilatory setting during neonatal mechanical ventilatory support.