Authors: Zazzeron L et al.
Anesthesiology, January 16, 2026, 10.1097/ALN.0000000000005939
This experimental study investigated whether long-term low-dose inhaled nitric oxide (NO) could improve pulmonary hypertension and cardiac dysfunction caused by chronic hypoxia and impaired lung development. The research is particularly relevant to newborns living at high altitude, where persistent low oxygen levels can disrupt lung growth and lead to pulmonary vascular disease.
Chronic hypoxia during early life can impair normal lung development, resulting in pulmonary vascular remodeling, increased pulmonary artery pressures, right ventricular hypertrophy, and eventually right heart failure. Nitric oxide is a key endogenous mediator of pulmonary vasodilation and plays an important role in maintaining healthy pulmonary circulation and supporting lung development. Although inhaled nitric oxide is commonly used for acute neonatal pulmonary hypertension, the potential benefits of prolonged low-dose therapy in chronic hypoxic conditions had not been well defined.
To investigate this question, the researchers used a murine model in which neonatal mice were exposed to chronic hypoxia beginning on postnatal day 3 to 4. Animals were maintained either in normal oxygen conditions (21% FiO₂) or in hypoxia (11% FiO₂). Within these groups, some mice received continuous inhaled nitric oxide at a concentration of 10 parts per million, while others did not.
Several physiologic and structural outcomes were assessed when the animals reached adulthood. The investigators measured exhaled nitric oxide levels and circulating nitric oxide metabolites (plasma nitrite and nitrate) to evaluate systemic NO signaling. Pulmonary hypertension and right ventricular function were assessed using echocardiography and invasive hemodynamic measurements. Histologic analysis was also performed to evaluate pulmonary vascular structure and alveolar development.
The study confirmed that chronic hypoxia impaired lung development and produced significant pulmonary hypertension in the mice. Hypoxia also reduced nitric oxide biomarkers, including exhaled NO and circulating nitrite and nitrate levels, indicating suppression of endogenous NO signaling pathways.
Long-term inhaled nitric oxide therapy partially reversed several of these abnormalities. Continuous exposure to low-dose inhaled NO restored nitric oxide biomarkers and significantly improved pulmonary hemodynamics. Mice treated with inhaled NO showed reduced pulmonary hypertension, decreased right ventricular hypertrophy, and improved right ventricular function compared with untreated hypoxic animals.
However, inhaled nitric oxide did not reverse the structural changes associated with impaired lung development. Histologic examination demonstrated persistent alveolar simplification and vascular rarefaction despite NO therapy. This finding suggests that while nitric oxide can improve pulmonary vascular tone and cardiac function, it does not correct the underlying developmental abnormalities in lung architecture caused by early hypoxia.
Overall, the results indicate that prolonged low-dose inhaled nitric oxide may provide physiologic benefit in chronic hypoxia-induced pulmonary hypertension by restoring nitric oxide signaling and improving right ventricular performance. However, the therapy does not appear to reverse structural defects in lung development.
The authors conclude that these findings support further investigation of chronic inhaled nitric oxide therapy as a potential treatment strategy for pulmonary hypertension associated with long-term hypoxia, such as that experienced by populations living at high altitude or by infants with developmental lung disease.
What You Should Know
Chronic hypoxia during early life can impair lung development and lead to pulmonary hypertension and right ventricular hypertrophy.
Nitric oxide is an important regulator of pulmonary vascular tone and normal lung physiology.
In this murine model, long-term inhaled nitric oxide improved pulmonary hypertension and right ventricular function.
Despite these benefits, nitric oxide therapy did not reverse structural abnormalities in lung development caused by chronic hypoxia.
These findings suggest that inhaled nitric oxide may be useful as a physiologic therapy but not a structural regenerative treatment.
Key Points
Chronic hypoxia reduced endogenous nitric oxide signaling and produced pulmonary hypertension in mice.
Continuous inhaled nitric oxide at 10 ppm restored nitric oxide biomarkers.
Inhaled nitric oxide significantly improved pulmonary hypertension and right ventricular function.
Right ventricular hypertrophy was reduced with nitric oxide therapy.
Structural lung abnormalities, including alveolar and vascular rarefaction, were not corrected by nitric oxide.
The results support further study of prolonged inhaled nitric oxide therapy in chronic hypoxic pulmonary disease.
Thank you to Anesthesiology for allowing us to summarize this article.