An Appraisal of Techniques for Administration of Gaseous Nitric Oxide

Abstract

Gaseous nitric oxide (NO) is a potent selective pulmonary vasodilator. When mixed with O2 for more than 10-15 minutes it forms toxic amounts of nitrogen dioxide (NO!). We describe two techniques to administer 20 parts per million (ppm) during mechanical ventilation. A technique using flows of NO and 02 at low pressure to drive a Siemens Servo 900C ventilator provided a constant inspired concentration of NO. Another technique in which NO was added to the inspiratory limb of a Siemens Servo 900C ventilator driven by high pressure oxygen provided a highly variable concentration (9-53 ppm) of inspired NO.

UK guidelines for the use of inhaled nitric oxide therapy in adult ICUs

“…The latter should be considered as the optimal method, as it allows servo-controlled injection of the nitric oxide/nitrogen mixture (NO/N2) into the inspiratory limb only during inspiration. This should reduce the bolus effect seen with continuous injection systems and may reduce nitrogen dioxide (NO2) formation because of decreased NO and oxygen mixing time [24][25][26][27]. The continuous injection system uses a calibrated flow meter with stainless steel needle valves to deliver a continuous flow of NO/N 2 throughout the respiratory cycle [24].…”

Technical considerations for inhaled nitric oxide therapy: time response to nitric oxide dosing changes and formation of nitrogen dioxide

“…The latter is important for the correct interpretation of omission trials which are recommended to be performed routinely as well as for the correct registration of dose-response curves. A disadvantage of application site A might be the intermittent occurrence of higher peak NO concentrations [6]. We assume however, that these NO boli are completely diluted by the residual air volume within the bronchial tree and the alveoli.…”

Generation of nitrogen dioxide during nitric oxide therapy and mechanical ventilation of children with a Servo 900C ventilator

“…We and others have previously described the delivery system for NO [10,13]. Separate sources of NO and of O 2 are mixed and directed immediately into the low pressure inlet of the ventilator, thus allowing a constant concentration of NO to be delivered during intermittent inspiratory flow to the patient.…”

“…The latter technique allows high concentrations of NO to accumulate in the inspiratory limb during the expiratory phase and results in peaks and troughs in NO delivery [13,14]. The addition of NO to the inspiratory limb of a continuous flow ventilator would not be expected to cause a similar problem.…”