Accurate and precise delivery of nitric oxide during high-frequency oscillatory ventilation.

Abstract

We have previously described a method for the precise delivery of inhaled nitric oxide (iNO) via a conventional, continuous-flow, pressure-limited, time-cycled ventilator. Because of the augmented effect of iNO decreasing pulmonary vascular resistance with high-frequency oscillatory ventilation (HFOV), we developed and bench tested a system that permits easy and accurate iNO delivery during HFOV. The system uses a mass flow controller to deliver fixed volumes of iNO to the HFOV circuit in the range 0 to 20 ppm iNO. The accuracy of the delivery system is based on a comparison of the difference between iNO measured at strategic points in the circuit and the calculated true value. The mean difference between the measured and calculated value for iNO (n = 360) was -0.2+/-1.74 ppm (2 SD) (range, 0 to 20 ppm, 0 to 15 Hz). The formation of nitrogen dioxide was <1 ppm at the level of the endotracheal tube. The method tests the accuracy of iNO measurements and provides an assessment of the uncertainty over the range of iNO and HFOV settings used clinically.