Addition of Nitric Oxide to Oxygen Improves Cardiopulmonary Function in Patients With Severe COPD: Conclusion
Our results suggest that inhaled NO should be studied as a supplement to oxygen therapy for the short-term treatment of acute exacerbations of pulmonary hypertension in patients with severe COPD. They further suggest that although a dose-dependent response of the pulmonary circulation could be anticipated, there is a ceiling effect on oxygenation at low levels (5 ppm), which may be consistent with the deterioration in Pa02 seen in studies using 40 ppm NO. Because improved oxygenation may itself decrease pulmonary vascular resistance, the relative benefits of 5 ppm NO (improved oxygenation with mild direct pulmonary vasodilation) vs 20 ppm NO (no further improvement in oxygenation but enhanced direct pulmonary vasodilation) should be examined.
On a more speculative level, it is conceivable that long-term administration of even low-dose (5 ppm) NO to patients receiving LTOT could enhance the beneficial effects of oxygen on pulmonary hypertension, right ventricular function, exercise tolerance, and survival. In our study, continuous measurement of NOx and intermittent sampling of methemoglobin did not reveal any propensity toward NO toxicity. Canadian health&care mall read more Indeed, there is little evidence for N O toxicity when NO concentration is <25 ppm. Frostell et al did not find any significant difference in extravascular lung water, NOx, or methemoglobin concentration in lambs breathing 80 ppm NO for 1 and 3 h. Animals have breathed the gas in concentrations of 10 to 40 ppm for 6 days to 6 months without evidence of toxic reactions. However, safe application of home NO inhalation awaits the development of reliable portable analyzers and long-term toxicology studies related to use of NO with special emphasis on its metabolic decomposition products.
In conclusion, we have demonstrated that when short-term inhaled NO is added to LTOT, there is an unequivocal improvement in oxygenation but a ceiling effect at 5 ppm. Pulmonary hemodynamics (pulmonary arterial pressure, vascular resistance, and right ventricular function) improved in a dose-dependent manner in the range of 5 through 20 ppm. Further studies are warranted to examine the usefulness of inhaled NO as a supplement to oxygen during acute exacerbations of COPD, or even the possibility of long-term application in patients receiving LTOT.