The Science Journal of the American Association for Respiratory Care
Background: We have previously investigated the fluctuation of nitric oxide concentration ([NO]) during inhaled NO therapy with conventional mechanical ventilation (Anesthesiology 1997; 86:676 and Chest 1998; 133:1650-1657). However, no study has reported the accuracy of NO delivery during HFO to determine whether [NO] fluctuates beyond the clinically acceptable range. The aim of this study was to evaluate the mixing of NO titrated into the HFO ventilator circuit at different sites using a rapid response [NO] analyzer. Method: An oscillator (Sensormedics 3100A, Yorma Linda CA) was set up in the usual manner to ventilate a test lung (compliance
Results: The figure shows target [NO] of 20 ppm, frequency 10 Hz, and mean airway pressure 20 cm H2O (closed bars for proximal sampling, gray bars for mid-sampling, and open bars for distal sampling). With NO injection after the bellows, the delivered [NO] at the mid and distal sampling sites was lower than target [NO] (> 5%). The INOvent delivered virtually the target [NO] at all conditions. The [NO2] was <1 ppm for all settings.
Conclusions: Mixing of NO was satisfactory, particularly when NO was titrated into the circuit before the humidifier. Comparable results occurred with the INOvent and titration of NO into the circuit. The levels of NO2 were low and acceptable.
(See Original for Figure)