Key Points
Nasal nitric oxide (NO) acts as our body’s first line of defense against airborne pathogens
Nasal NO reduces blood pressure, redistributes blood flow, and increases gas exchange
The humidifying effects of the nose might not be as important as NO
The Breathing Diabetic Summary
Nitric oxide (NO) has, somewhat quietly, become a staple of breathing science. NO is produced in the nasal airways and carried into the lungs with each (nasal) breath we take. This review discussed nasal NO, its origins, and its physiological effects in the body.
The general consensus is that NO is produced in the paranasal sinuses and is continuously released into the nasal airways. Because of this continuous release, NO’s concentration is dependent on flow rate. A lower flow rate will allow more NO to build up, thus bringing higher concentrations down into the lungs with each breath.
This could be yet another benefit of slow breathing: Slower flow rates will increase NO. Each breath then brings in a higher concentration of NO, redistributing blood flow, increasing gas exchange, and potentially increasing infection-fighting capabilities.
Which brings us to the next physiological effect of nasal NO: Host defense. Some bacteria die when NO concentrations are as low as 100 parts per billion (ppb). In the paranasal sinuses, the concentration can be as great as 30,000 ppb(!). Thus, nasal NO might be the first line of defense against airborne bacteria, acting to sterilize the incoming air and reduce infection.
Nasal NO also increases arterial oxygenation and reduces blood pressure in the lungs. For example, one study showed that nasal breathing increased tissue oxygenation by 10% when compared to mouth breathing. That’s pretty remarkable.
For example, one study showed that nasal breathing increased tissue oxygenation by 10% when compared to mouth breathing.
Another study showed that when mouth breathers were given supplemental NO, arterial oxygenation increased and and lung blood pressure decreased similar to nose breathing. Interestingly, if the mouth breathers were just given moistened air (without NO), these effects did not occur. Thus, the main benefits of nasal breathing might be due to NO, not the warming and humidifying effects that are typically touted (although they clearly help).
Finally, widening the nostrils via nasal tape also increases arterial oxygenation during breathing at rest. This could partially be due to an increased delivery of NO to the lungs. We can naturally unblock our noses using simple breath hold techniques or use something like Intake Breathing for assistance.
Overall, this study highlighted several important aspects of nasal NO. It acts as our body’s first line of defense against airborne pathogens by sterilizing incoming air. Then, as NO travels into the lungs, it reduces blood pressure, redistributes blood flow, and increases gas exchange, leading to greater arterial oxygenation. Finally, we learned that the humidifying effects of the nose might not be as important as NO.
I am continually amazed by the many roles of nitric oxide in the body. I believe it might be the most important aspect of nasal breathing.
Journal Reference:
Lundberg JO, Weitzberg E. Nasal nitric oxide in man. Thorax. 1999;54(10):947-52.