Nasal breathing is more than a passive intake of oxygen; it is a complex physiological defense mechanism. The nasal cavity functions as a sophisticated climate control system, filtering, warming, and humidifying incoming air to prepare it for the delicate tissues of the lungs (Holden et al., 2009). Beyond simple filtration, the paranasal sinuses continuously produce Nitric Oxide (NO), a potent signaling molecule. When you breathe through your nose, this reservoir of NO is swept into the lungs—a process known as “autoinhalation”—which helps sterilize incoming air and combat pathogens (Martel et al., 2020).
The physiological impact of this inhaled Nitric Oxide is profound. Once it reaches the lungs, NO acts as a selective vasodilator, expanding the blood vessels in the pulmonary circulation to increase blood flow and enhance oxygen uptake (Lundberg et al., 1996). Research indicates that this mechanism can significantly improve arterial oxygenation and reduce pulmonary vascular resistance, effectively lowering the workload on the heart (Sánchez Crespo et al., 2010). Mouth breathing bypasses this entire system, depriving the body of this naturally produced vasodilator and reducing overall oxygen efficiency.
Chronic mouth breathing also carries significant risks for oral health and sleep quality. Saliva provides a protective barrier against bacteria; however, mouth breathing causes rapid evaporation, leading to xerostomia (chronic dry mouth), which significantly increases the risk of dental caries, gum disease, and halitosis (Maniaci et al., 2024). Furthermore, mouth breathing during sleep is strongly correlated with sleep-disordered breathing and obstructive sleep apnea (OSA), as the open mouth position alters upper airway muscle tone and increases the likelihood of airway collapse (Schroeder & Gurenlian, 2019). If you wake up with a dry mouth, it is a clear indicator that your sleep physiology and oral microbiome are being compromised.
References
- Holden, W. E., Sippel, J. M., Nelson, B., & Giraud, G. D. (2009). Greater nasal nitric oxide output during inhalation: Effects on air temperature and water content. Respiratory Physiology & Neurobiology, 165(1), 22–27. https://doi.org/10.1016/j.resp.2008.09.009
- Lundberg, J. O. N., Settergren, G., Gelinder, S., Lundberg, J. M., Alving, K., & Weitzberg, E. (1996). Inhalation of nasally derived nitric oxide modulates pulmonary function in humans. Acta Physiologica Scandinavica, 158(4), 343–347. https://doi.org/10.1046/j.1365-201x.1996.557321000.x
- Maniaci, A., Lavalle, S., Anzalone, R., Lo Giudice, A., Cocuzza, S., Parisi, F. M., Torrisi, F., Iannella, G., Sireci, F., Fadda, G., Lentini, M., Masiello, E., & La Via, L. (2024). Oral health implications of obstructive sleep apnea: A literature review. Biomedicines, 12(7), 1382. https://doi.org/10.3390/biomedicines12071382
- Martel, J., Ko, Y.-F., Young, J. D., & Ojcius, D. M. (2020). Could nasal nitric oxide help to mitigate the severity of COVID-19? Microbes and Infection, 22(4), 168–171. https://doi.org/10.1016/j.micinf.2020.05.002
- Sánchez Crespo, A., Hallberg, J., Lundberg, J. O., Lindahl, S. G. E., Jacobsson, H., Weitzberg, E., & Nyrén, S. (2010). Nasal nitric oxide and regulation of human pulmonary blood flow in the upright position. Journal of Applied Physiology, 108(1), 181–188. https://doi.org/10.1152/japplphysiol.00285.2009
- Schroeder, K., & Gurenlian, J. R. (2019). Recognizing poor sleep quality factors during oral health evaluations. Clinical Medicine & Research, 17(1–2), 20–28. https://doi.org/10.3121/cmr.2019.1465
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