Producing nitric oxide by pulsed electrical discharge in air for portable inhalation therapy

Generating nitric oxide from air by pulsed electrical discharge produces therapeutic levels of nitric oxide for inhalation and provides effective pulmonary vasodilation. Breath of fresh NO Inhalation therapy—an expensive, yet life-saving, treatment for pulmonary hypertension—is not common in many parts of the world or in patients’ homes. To make inhaled nitric oxide (NO) available to all, at the bedside, Yu et al. designed a lightweight, portable system that created NO from ambient air or oxygen-nitrogen mixtures. Their generator used a pulsed electrical spark from an iridium electrode to create gaseous NO, pump it through a scavenger (to remove toxic gases like ozone), and then deliver it constantly or only during inspiration. The device was designed to have all components, including the scavenger, inline, making it self-contained and portable. The NO produced was equivalent to NO delivered from a cylinder, the current clinical gold standard, when treating lambs with pulmonary hypertension. It is hoped that this new economical technology for NO inhalation therapy will liberate patients from costly, cumbersome tanks and complicated delivery and monitoring systems, in emergency situations and in their own homes. Inhalation of nitric oxide (NO) produces selective pulmonary vasodilation and is an effective therapy for treating pulmonary hypertension in adults and children. In the United States, the average cost of 5 days of inhaled NO for persistent pulmonary hypertension of the newborn is about $14,000. NO therapy involves gas cylinders and distribution, a complex delivery device, gas monitoring and calibration equipment, and a trained respiratory therapy staff. The objective of this study was to develop a lightweight, portable device to serve as a simple and economical method of producing pure NO from air for bedside or portable use. Two NO generators were designed and tested: an offline NO generator and an inline NO generator placed directly within the inspiratory line. Both generators use pulsed electrical discharges to produce therapeutic range NO (5 to 80 parts per million) at gas flow rates of 0.5 to 5 liters/min. NO was produced from air, as well as gas mixtures containing up to 90% O2 and 10% N2. Potentially toxic gases produced in the plasma, including nitrogen dioxide (NO2) and ozone (O3), were removed using a calcium hydroxide scavenger. An iridium spark electrode produced the lowest ratio of NO2/NO. In lambs with acute pulmonary hypertension, breathing electrically generated NO produced pulmonary vasodilation and reduced pulmonary arterial pressure and pulmonary vascular resistance index. In conclusion, electrical plasma NO generation produces therapeutic levels of NO from air. After scavenging to remove NO2 and O3 and filtration to remove particles, electrically produced NO can provide safe and effective treatment of pulmonary hypertension.