Background: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.Method: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.Results: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.Conclusion: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.