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Accurate and precise delivery of nitric oxide during high-frequency oscillatory ventilation
1Department of Pediatrics, The Milton S. Hershey Medical Center, Pennsylvania State University College of Medicine, Hershey 17033, USA.
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.