Nitric oxide unravels the enigmatic function of the paranasal sinuses: a review of literature

Abstract

Background: The physiological functions of the paranasal sinuses are as yet unclear, and it is often assumed that these empty air-filled spaces have no vital function in our body. Recently, nitric oxide has been reported to be synthetized in high concentration by the paranasal sinuses which seems to be the main function of these air-filled empty spaces. Body of abstract: The functional role of the paranasal sinuses is still ambiguous despite the several hypotheses that have been put forward to justify their existence. Although it has been recently demonstrated that the paranasal sinuses produce large amounts of nitric oxide (NO), otolaryngologists overwhelmed by attempting to unravel the enigmatic etiology underlying chronic rhinosinusitis have interpreted the high NO output in this context. Nevertheless, NO prime function is vasodilation and has long been recognized to be produced by the endothelial cells. In this review, evidence in the literature is piled and pieces of the puzzle are put together to show that NO synthesized in the paranasal sinuses functions as an airborne messenger that induces pulmonary vasodilation and thereby decreases the workload on the heart. Recognition that the paranasal sinuses are in fact an organ with known function is likely to foster further research and has an impact on our current surgical philosophy. Conclusion: The paranasal sinuses seem to play a vital physiological role in our body rather than being evolutionary remnants as initially thought. They are likely responsible for regulating the pulmonary blood pressure thereby preventing pulmonary hypertension.

Nitric Oxide, Humming and Bhramari Pranayama

“…NO could also act as a defense mechanism in the upper airways by modulating the ciliary motility and low levels of NO can be linked to weakened mucociliary activity (5) . Numerous bacteria and many airway pathogens are sensitive to NO gas in concentrations as low as 100 ppb (6) , and the level of NO in the healthy maxillary sinuses is much higher than this. Nasal NO levels are generally very low in patients suffering from sinusitis of different etiology.…”

“…Part of the gas leaked to the nasal cavity is diluted in the inhaled breath and is transported by the airstream to the lungs. It is tempting to conjecture that the production of NO in the paranasal sinuses has the purpose of modulating lung function in humans which reduces pulmonary vascular resistance and thus the workload of the heart (6) . NO inhaled from a proximal source will affect pulmonary vessels in contact with ventilated alveoli, thereby improving ventilation/perfusion matching and also reducing vascular resistance.…”

“…It is also postulated that nasal Nitric Oxide output is considerably greater during inhalation than exhalation in healthy adults (6) . The ostial opening of the sinuses which oscillate to acoustic vibration is said to respond to humming during inhalation similar to humming during exhalation as already observed in various experiments (15) .…”