Nasal breathing is an extremely popular up and coming protocol with various cardio/conditioning performances to optimise our breathing function and possible beneficial health effects. The issue is that people are quick to jump on the band wagon before doing their own research, and so I am going to clear up the literature, outlining any pros and cons of the popular method of breathing. ‘Normal’ breathing, despite being normal, is actually quite uncommon. As you have heard me say before, just because something is common, it doesn’t necessarily mean it’s normal, so this is kind of the flip of that phrase. Most subjects spontaneously breathed with their mouths open when instructed to breathe "naturally." Subsequently, when they were required to breathe only through the nose during the exercise, an almost complete inhibition of the post-exercise bronchoconstrictive airway response was demonstrated [1]. When instructed to breathe only through the mouth during exercise, an increased bronchoconstrictive airway response occurred, as measured by spirometry, flow-volume relationships, and body plethysmography.
So here are the popular beliefs of what nasal breathing can achieve.
Prepares the air before entering the lungs:
Nasal breathing will promote the air we breath to be cleansed before reaching our lungs. The nose is the only organ that can properly perform this function. The internal lining of the nose has hair, called cilia, that act as filters, while humidifying, and warming or cooling the air we intake. The paranasal sinuses of the nose produce nitric oxide [2], which is harmful to bacteria, viruses and other microbes that could enter the nasal passage way. Essentially breathing through the mouth would bypass these crucial steps for preparing the air we breathe to lower the level of possible damage caused by dirt or pathogenic air.
https://entokey.com/nasal-physiology/
Keeps you calm:
Quite simply, nasal breathing requires you to take bigger, deeper breaths. Without the large opening of the mouth drawing in excessive amount of oxygen, the breath through the nose has to be longer and deeper to accrue the same amount of required oxygen. This process drives oxygen into the lower lobes of the lungs where calming nerves of the PsNS can be activated. The pulmonary parasympathetic nervous system (left and right vagus nerves) lie deeper than the sympathetic fibres of the lungs. So now you know why when people are stressed, they are told to slow down and ‘take a deep breath’ (Yes, some old wives tales are true, although most don’t understand the mechanisms of their advice when advising).
Oxygen Utilisation Efficiency:
When we breathe, we utilise oxygen from the air, and this normally happens on the exhale, when the lungs take the oxygen from the air with help from our little alveoli. Nasal breathing slows the air escape so the lungs have more time to perform this mechanism. When there is proper oxygen-carbon dioxide exchange, the blood will maintain a balanced PH. If carbon dioxide is lost too quickly (when we orally breathe) oxygen absorption is decreased. However, does this mean we have more aerobic and anaerobic power output, thus improved performance? Not necessarily. Hall asked participants to perform exercise on a cycle ergometer at 60% of their maximum heart rate and concluded that oral breathing resulted in a higher ventilation volume and uptake of oxygen in comparison to nasal breathing [3]. Based on RER data they found that nasal breathing did significantly reduce hyperventilation, however this made relatively little difference on power output and performance measures.
Detoxification: Removal of excess CO2
We have little air sacs in our lungs called Alveoli, which have a big influence on the clearance of CO2. Alveoli pick up the incoming energy (oxygen) we breathe and release the outgoing waste product (CO2) we exhale. If this process was impaired and we had excess retention of CO2 in our body, we would enter a state on hypercapnia (excess CO2), and would experience symptoms like fatigue, dizziness, headaches, or some more serious conditions like seizures and loss consciousness. 60-80% of these alveoli are situated in the lower lobes of the lungs, you are therefore clearing the waste from your blood more completely when we inhale deeply, sending the air to the lower parts go the lungs. Recently, nasal high flow (NHF) has been introduced in acute setting in adults [4], too. It is an open nasal cannula system for delivering warm and humidified air or oxygen at high flow rates (2–50 L/min) assisting ventilation. It was shown that this treatment can improve hypercapnia. It is theorised that NHF assisted ventilation through clearance of anatomical dead space, which improves alveolar ventilation.
https://favpng.com/png_view/vector-eye-pulmonary-alveolus-gas-exchange-lung-capillary-respiration-png/XRHMm7t3
Lymph node stimulation:
Dr. Jack Shields, a prominent lymphologist, conducted a study in 1979 that showed deep diaphragmatic breathing causes the lungs to press into the thoracic duct (after its purification by lymph nodes etc.) which presses the fluid from there back into the blood stream where it belongs. With deep, efficient nasal breathing especially during exercise, the rib cage acts as a lymphatic pump designed to move toxic waste out of the heart and lungs and pull toxic lymph from various parts of your body. However, is there a difference between a nasal breath or an orally inhaled breath to promote distended diaphragm? Probably not, so the requirement of nasal breathing for mediating lymph node activity is somewhat a bias.
[1] Bronchoconstriction: Shturman-Ellstein R, Zeballos RJ, Buckley JM, Souhrada JF. The beneficial effect of nasal breathing on exercise-induced bronchoconstriction. Am Rev Respir Dis. 1978;118(1):65-73. doi:10.1164/arrd.1978.118.1.65
[2] Lundberg JO, Settergren G, Gelinder S, Lundberg JM, Alving K, Weitzberg E. Inhalation of nasally derived nitric oxide modulates pulmonary function in humans. Acta Physiol Scand. 1996;158(4):343-347. doi:10.1046/j.1365-201X.1996.557321000.x
[3] Hall RL. Energetics of nose and mouth breathing, body size, body composition, and nose volume in young adult males and females. Am J Human Biol. 2005;17(3):321–330
[4] Fricke K, Tatkov S, Domanski U, Franke KJ, Nilius G, Schneider H. Nasal high flow reduces hypercapnia by clearance of anatomical dead space in a COPD patient. Respir Med Case Rep. 2016;19:115-117. Published 2016 Aug 26. doi:10.1016/j.rmcr.2016.08.010
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