“…The goal of EES is to increase ventilation and drainage of the paranasal sinuses (PNS) involved, enabling the proper functioning of mucociliary movements in the nasal and PNS mucosa, thus facilitating the drainage of these cavities and enabling the penetration of medication and solutions for nasal flushing [1][2][3][4] . This method, despite bearing numerous benefits when compared to the conventional open procedures, still has some inherent challenges and limitations, especially because it ends up removing bone tissue and nasal mucosa fragments, which can cause bleeding, temporary physiological changes to the nasosinusal mucosa, especially the paradox reduction of mucociliary movements in the post-operative period and local scar fibrosis, which can cause re-obstruction of the treated PNS 1,2 . The recent finding of high levels of nitric oxide (NO) in the nose and PNS in healthy persons in comparison with the tracheobronchial tree is also a current object of study; nonetheless, very little is known about the role of this gas in the nose and PNS, and which are the clinical and surgical implications of this substance in the upper airways.…”