Key Points
Nasal nitric oxide (NO) acts as our first line of defense against airborne pathogens by sterilizing incoming air and enhancing cilia movement
Nasal NO plays a role in warming the air we breathe as it travels into the lungs
Humming significantly increases nasal NO and could be used as a test for sinus disorders
The Breathing Diabetic Summary
I spend a lot of time reading about nitric oxide (NO). But, the more I learn, the more interested I become. It seems to pop up everywhere I look. Sometimes I wonder what it can’t do.
Nitric oxide’s physiological relevance was discovered in 1987, the same year I was born. Its effects were known several years prior, but it wasn’t until two separate papers (both in prestigious journals, PNAS and Nature) were published that NO’s benefits became “official.”
In the respiratory system, the primary source of NO is the upper airways. The paranasal sinuses, in particular, produce ~90% of the NO measured in exhaled air.
Previously, we have learned that NO acts as our first line of defense against airborne pathogens by sterilizing incoming air. The breathing community often touts aspect of NO. Here, we learn there is more to it: nitric oxide also increases the cilia motility.
Cilia are tiny hairs lining the back of your nose and respiratory tract. They oscillate back and forth to move mucus out of the upper and lower airways, bringing pathogens and other potentially harmful agents along for the ride. Cilia are your lung’s first defense against inhaled particles and nitric oxide enhances their activity.
Nitric oxide also plays a role in warming incoming air. The precise mechanism is unclear, but increased nasal NO release is associated with increased temperature in the nasal airways.
Here is my speculation: NO increases blood flow in your nose, which warms the nasal passages and airways. As air travels through, it extracts this warmth before entering the lungs. Makes sense, but is just a hypothesis and likely oversimplifies what is going on…
Nasal nitric oxide also redistributes blood flow in the lungs when in the upright position, leading to better oxygen uptake. (Nasal NO might even be an adaptation to gravity, allowing us to walk upright.)
Finally, humming causes a significant increase in nasal NO. However, some sinus disorders inhibit this enhanced NO release. Therefore, the measurement of nasal NO after humming might be a way to test for sinus disorders.
To summarize, nasal nitric oxide is a powerful gas. It acts as our first line of defense against airborne pathogens by sterilizing incoming air and by improving cilia motility. Additionally, NO helps warm the air we breathe as it travels into our lungs. NO also redistributes blood flow in the lungs, resulting in better oxygen uptake. Lastly, humming increases NO significantly and might provide a way to test for sinus disorders.
Abstract
Exhaled nitric oxide (NO) originates from the upper airways, and takes action, to varying extents, in regulation, protection and defense, as well as in noxious processes. Nitric oxide retains important functions in a wide range of physiological and pathophysiological processes of the human body, including vaso-regulation, antimicrobial activity, neurotransmission and respiration. This review article reports the ongoing investigations regarding the source, biology and relevance of NO within upper respiratory tract. In addition, we discuss the role of NO, originating from nasal and paranasal sinuses, in inflammatory disorders such as allergic rhinitis, sinusitis, primary ciliary dyskinesia, and cystic fibrosis.
Journal Reference:
Maniscalco M, Bianco A, Mazzarella G, Motta A. Recent Advances on Nitric Oxide in the Upper Airways. Curr Med Chem. 2016;23(24):2736-2745.