OBJECTIVE: The objective of our study was to evaluate the precision and safety of administering nitric oxide (NO) during full and partial ventilatory support. METHODS: NO was administered either using a microprocessor-controlled servo ventilator, substituting an NO-N2 mixture for the ventilator's usual air supply or by adding an NO-N2 mixture with a constant flow at the proximal end of the tracheal tube. NO, nitrogen dioxide (NO2), and nitrous and nitric acid (HNOx) was quantified selectively with a sequential, selective, hollow tube preconcentration and chemiluminescence analysis in a respiratory system model during various modes of full and partial ventilatory support. RESULTS: The servo valve system of the ventilator provided accurate NO concentrations during full and partial ventilatory support. Interaction of spontaneous and mechanical ventilation during partial ventilatory support resulted in irregular inspiratory flow patterns and a difference of 3.6% to 44.1% between the desired and measured inspiratory NO concentrations when NO was administered at a constant flow to the proximal end of the tracheal tube. NO2 was not detected. Small amounts of 0.6 to 0.8 ppm HNOx were detected when 80 ppm NO was administered in a humid gas mixture of 37 degrees C in the presence of 90% oxygen. CONCLUSIONS: NO can be administered accurately without formation of NO2 during full and partial ventilatory support with the electronically controlled valve system of the ventilator. Formation of HNOx is a potential problem at high NO and O2 concentrations in the presence of moisture.
OBJECTIVE: The objective of our study was to evaluate the precision and safety of administering nitric oxide (NO) during full and partial ventilatory support. METHODS: NO was administered either using a microprocessor-controlled servo ventilator, substituting an NO-N2 mixture for the ventilator's usual air supply or by adding an NO-N2 mixture with a constant flow at the proximal end of the tracheal tube. NO, nitrogen dioxide (NO2), and nitrous and nitric acid (HNOx) was quantified selectively with a sequential, selective, hollow tube preconcentration and chemiluminescence analysis in a respiratory system model during various modes of full and partial ventilatory support. RESULTS: The servo valve system of the ventilator provided accurate NO concentrations during full and partial ventilatory support. Interaction of spontaneous and mechanical ventilation during partial ventilatory support resulted in irregular inspiratory flow patterns and a difference of 3.6% to 44.1% between the desired and measured inspiratory NO concentrations when NO was administered at a constant flow to the proximal end of the tracheal tube. NO2 was not detected. Small amounts of 0.6 to 0.8 ppm HNOx were detected when 80 ppm NO was administered in a humid gas mixture of 37 degrees C in the presence of 90% oxygen. CONCLUSIONS: NO can be administered accurately without formation of NO2 during full and partial ventilatory support with the electronically controlled valve system of the ventilator. Formation of HNOx is a potential problem at high NO and O2 concentrations in the presence of moisture.